Final Document Dissertation Paramesh Nirmal

Northumbria University Final Year Project 2009-2010

Paramesh Nirmal

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CEIS

Flow measurement around typical car shapes using a wind tunnel

BENG (Honours) Mechanical Engineering

-Paramesh Nirmal

28th March 2010

ABSTRACT Car designers have been testing their designs in various ways to understand the airflow around it. With the knowledge, they have been attempting to improve the vehicles aerodynamics in every way possible. Since the early 1900s, better aerodynamics has progressed towards being the chief goal in terms of car design. The aim of this project is to investigate the flow around typical car shapes using a Wind Tunnel. The analysis will be carried out in two dimensions, the maximum speed of the wind tunnel is 15 m/s which accounts to around 40 km/h. A Pitot tube will be used to measure pressure and velocity around the car shapes. The three typical car shapes that are investigated are the Saloon, Hatchback and Fastback. The results will be analysed and also be compared with results from numerical testing done using Computational Fluid Dynamics (CFD). The investigation showed that the rear shape of the car causes low pressure in the rear region leading to recirculation of air. The results also showed that the data obtained from the Pitot tube is only reliable when measuring uniform flow in one direction.

Supervisor: Dr. Reaz Hasan


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Acknowledgments

The author would like to show gratitude to his supervisor Dr Reaz Hasan for his consistent support

and guidance throughout the study. Also thanks to Dr Roger Penlington for his assistance in the use

of CFD and for his guidance with using the instruments.

Appreciation is also extended to Dr Phillip Hackney for his aid towards fabricating the car shapes.

Finally the author would like thank his colleagues for their encouragement all through the

completion of this project.


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List of Figures

Fig.# Description

1.1 The four primary phases of Aerodynamics

1.2 Torpedo Shape Vehicle (1899)

1.3 Air-ship shape vehicle (1913)

1.4 Boat-tail Shape Vehicle (1913)

1.5 Drag Measurements of Jaray Cars (1922)

1.6 Comparison of rear-end shapes

1.7 Design phases of a car shape

1.8 The change in shapes of the Porsche car models from 1950 to 1981.

1.9 The flow around a passenger car

2.0 Wind tunnel

2.1 2-dimensional measurement in a wind tunnel

2.2 2-dimensional hatchback

2.3 Points on Hatchback

2.4 Total Pressure Readings

2.5 A limitation of the Total Head tube

2.6 Hatchback constructed in Solidworks

2.7 Fastback constructed in Solidworks

2.8 Saloon constructed in Solidworks

2.9 Static Pressures measured on Hatchback

3.0 Experimental data of Fluid velocity around Hatchback in a wind tunnel (steady)

3.1 Experimental data of Fluid velocity around Hatchback in a wind tunnel (erroneous)

3.2 Points on Hatchback (reference for fig. 3.0 and 3.1)

3.3 Total Pressure contours on FLUENT

3.4 Attempt to elevate car on a platform on CFD.

3.5 Hatchback mesh setup

3.6 Fine Mesh

3.7 Defining Boundary Conditions

3.8 Lines created on FLUENT

3.9 x-velocity contours on hatchback

4.0 Height vs Velocity (Point 3.5 on Hatchback)

4.1 Contours of Static Pressure for the hatchback on FLUENT

4.2 Height vs. Static Pressure on Hatchback

4.3 x-velocity vectors at rear end of Hatchback

4.4 Contours of Turbulent Intensity on Hatchback

4.5 Height vs. Static Pressure for Pitot tube placed in opposite directions

4.6 Turbulent Intensity contours around a saloon shape

4.7 Contours of static pressure around a saloon shape

4.8 Contours of turbulent intensity around a fastback shape

4.9 Contours of Static pressure around a fastback shape

5.0 x-velocity vectors in rear region of fastback shape


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5.1 Turbulent Recirculation length (Hatchback)

5.2 Turbulent Recirculation length (Fastback)

5.3 Turbulent Recirculation length (Saloon)

5.4 Turbulent intensity at rear region of Saloon.

5.5 Holes to place dowels

5.6 Wind Tunnel Chamber

5.7 Non-streamlined platform

5.8 Streamlined platform

5.9 Wind tunnel apparatus

6.0 Inclined manometer

6.1 Inclined manometer setting

6.2 Height gauge, accurate to one hundredth of a mm 6.3 Static Pressure Errors

6.4 Case 1: measuring pressure at front of car using Pitot Tube 6.5 Case 2: measuring pressure at front of car using a total pressure

tube 6.6 Ford Fiesta (Hatchback) www.dekstopmachine.com

6.7 Ford GT40 (Fastback) www.dekstopmachine.com

6.8 Lincoln Town Car (Saloon) www.dekstopmachine.com

List of Tables

Table # Description

1 List of Coordinates

2 Velocity and Static Pressure Readings for Point 3.5 on Hatchback

3 Dynamic Head at Rear of Car (experimental results).

4 Static Pressure at point 0 on Hatchback (experimental results).

5 Empirical results for Hatchback. Wind Tunnel Setting: 8.5 m/s.

6 Empirical Results for Fastback. Wind tunnel setting: 8.5m/s.

7 Preliminary Readings

8 Estimated project costing.


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List of Notation

v Experimental air velocity m/s u0 Air inlet velocity m/s ρ Air Density kg/m3

u CFD air velocity m/s PTotal Total Pressure N/m2 PDyn Dynamic Pressure N/m2 PStat Static Pressure N/m2 l Length of car mm Pref Reference Point Pressure N/m2 uref Reference Point Velocity m/s cp Pressure Coefficient Dimensionless


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Table of Contents

CHAPTER 1 PROJECT BACKGROUND AND RESEARCH .......................................................... 8

1.1 Introduction ................................................................................................................................................. 8

1.2 Literature Review ......................................................................................................................................... 9

CHAPTER 2 PROPOSED PROJECT WORK............................................................................ 16

2.1 Project Aims ............................................................................................................................................... 16

2.2 Objectives .................................................................................................................................................. 16

CHAPTER 3 EXPERIMENTAL METHOD: .............................................................................. 17

3.1 Introduction. .............................................................................................................................................. 17

3.2 Instruments. ............................................................................................................................................... 17

3.2.1 Pitot Tube. ........................................................................................................................................... 17

3.2.2 Accuracy of Total Head tube. ............................................................................................................... 20

3.2.3 Height gauge ....................................................................................................................................... 22

3.3 Car Shapes.................................................................................................................................................. 22

3.4 Speed ......................................................................................................................................................... 24

3.5 Number of Readings................................................................................................................................... 24

3.6 Results........................................................................................................................................................ 25

3.6.1 Static Pressure ..................................................................................................................................... 25

3.6.2 Velocity ............................................................................................................................................... 26

CHAPTER 4 NUMERICAL METHOD: ................................................................................... 28

4.1 Introduction ............................................................................................................................................... 28

4.2 Fluent Results............................................................................................................................................. 28

4.2.1 x-velocity ............................................................................................................................................. 28

4.2.2 Static Pressure ..................................................................................................................................... 29

4.2.3 Turbulence intensity ............................................................................................................................ 29

4.3 Two dimensional mesh set-up using ICEM CFD .......................................................................................... 29

4.4 Two dimensional analysis in FLUENT ......................................................................................................... 31

4.4.1 Boundary Conditions ........................................................................................................................... 31

CHAPTER 5 RESULTS AND DISCUSSION ............................................................................. 32


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5.1 Introduction ............................................................................................................................................... 32

5.2 Velocity ...................................................................................................................................................... 35

5.3 Static Pressure (ps) ..................................................................................................................................... 37

5.4 Rear End ..................................................................................................................................................... 38

5.5 Saloon and Fastback .................................................................................................................................. 42

5.5.1 Saloon ................................................................................................................................................. 42

5.5.2 Fastback .............................................................................................................................................. 43

5.6 Recirculation Length (RL) ........................................................................................................................... 45

CHAPTER 6 CONCLUSION ................................................................................................. 48

CHAPTER 7 RECOMMENDATION FOR FURTHER STUDIES .................................................. 49

REFERENCES..................................................................................................................... 50

CHAPTER 8 APPENDIX: ..................................................................................................... 54

8.1 Separation: ................................................................................................................................................. 54

8.2 Design of experimental components: ........................................................................................................ 54

8.3 Design the Test Rig. .................................................................................................................................... 55

8.4 Choosing correct Material. ......................................................................................................................... 55

8.5 Building the components. .......................................................................................................................... 56

8.6 Assembling the components. ..................................................................................................................... 57

8.7 Total Pressure Tube: .................................................................................................................................. 57

8.8 Manometer setting: ................................................................................................................................... 58

8.9 Height Gauge: ............................................................................................................................................ 59

CHAPTER 9 APPENDIX II ................................................................................................... 60

9.1 Pitot Tube Limitations ................................................................................................................................ 60

9.2 Car Shapes.................................................................................................................................................. 62

CHAPTER 10 APPENDIX III ................................................................................................ 64

10.1 Project Costing ......................................................................................................................................... 77


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Chapter 1 Project Background and Research

1.1 Introduction The shape of a car greatly affects its aerodynamic performance. A less ‘streamlined’ vehicle would

be less aerodynamic hence it would have an increased amount of drag towards the wind. A

streamlined vehicle would be a vehicle that has less sharp corners on its body, less ‘box like’ shapes,

etc.

Since the late 19th century and the 20th century, automobile manufacturers have made efforts to

improve the aerodynamics of vehicles.

The performance, handling and comfort of an automobile are significantly affected by its

aerodynamic properties. A low drag is a significant requirement for good fuel economy. Increasing

fuel prices and stringent legal regulations ensure that this long-established relationship becomes

more widely acknowledged.

Initial development concentrated entirely on drag, and other problems such as cross-wind sensitivity

only became significant with increasing driving speeds. Lately attempts have been made, by suitable

shaping, to eliminate the deposition of dirt and water of the windows and lights; leading to a

‘smoother’ shape and low drag.

Fig. 1.1. The four primary phases of Aerodynamics [1]


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Fig. 1.3 Air-ship shape vehicle (1913) [1]

Fig. 1.4 Boat-tail Shape Vehicle (1913) [1]

1.2 Literature Review Dating from the turn of the 20th century, an attempt was made to apply the automobile

‘streamlined’ shapes from the other authorities such as naval architecture and airship engineering.

Due to poor roads and low engine power, speeds were still so low that aerodynamic drag only

played a subordinate role. Most cars derived from these basic shapes had one error in common:

they neglected the fact that the flow past a body of revolution is no longer axially symmetrical when

the body is close to the ground and when wheels and axles are added.

The shapes of the vehicles did lead to gradual aerodynamic success (torpedo and air ship shapes),

however due to low speeds they were nearly ineffective.

In contrasts to the shapes shown in fig 1.2 and fig 1.3 the ‘boat tail’ is solely unproductive in terms of

aerodynamics (fig 1.4). The flow, separating at the front and from the wheel arches, will not re-

attach due to ‘boat tailing’ the rear end. The boat tail, which was applied in different variants on

mass-production of limos and sports cars, is

an example of how aerodynamic arguments

are often misused to justify stylistic

curiosities. [2]

After World War I, E. Rumpler developed several

vehicles which he called ‘teardrop cars’. [1]

The Teardrop shape was claimed to be the most

aerodynamic shape that can be developed.

However, on the Rumpler car the wheels are

uncovered, resulting in an increase in drag, which

becomes more significant as the aerodynamic

quality of the vehicle body improves.

P. Jaray was the first person to recognise that the

flow around a body of revolution, which has a

very low drag coefficient in free air, is no

longer axially symmetrical when close to

the ground.

After wind tunnel tests performed by

Klemperer at Jaray’s request, Jaray

assembled individual aerodynamically

shaped bodies which were later used again

and again by a number of designers.

Fig. 1.2 Torpedo Shape Vehicle (1899) [1]


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Fig. 1.5 Drag Measurements of Jaray Cars

(1922) [1]

Jaray considered that “low drag can only be achieved when the separation at the rear end is

eliminated and this can be achieved only with a very long, slender tail”. Jaray cars weren’t too

popular at their time they were not readily accepted by the public. Only several prototypes were

built by many manufacturers in Europe and the U.S. However, they showed a progress in

aerodynamics.

Jaray’s ideas were denied great success

because his cars had a relatively large length:

height ratio.

However, Lay working at Michigan University

started to get close to achieving a low drag

coefficient for his car shapes. Unfortunately,

Lay’s model had “parallel side walls and sharp

corners, which resulted in a fairly high drag

and limited the significance of his findings”.

The Most important result of Lay’s work was

that a blunt rear end resulted in only a

relatively small increase in drag in

comparison to a long tapered rear end.

The blunt rear end shape which Lay proposed

led to the development of the ‘Kamm-back’

shape. The Kamm-back, Lay’s blunt back and

Klemperer’s long tail design are shown in Fig.

1.6 The flow remains attached for as long as possible until is separated at the rear end as the cross

sectional area decreases on approach, resulting in low drag. W. Kamm was the first to investigate

the rear end design of motor vehicles in 1935 leading to the first passenger vehicle with a Kamm

read end being built in 1938. [1] Fig. 1.6 illustrates the differences between Kamm, Jaray and

Klemperer’s read end shapes:


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Fig. 1.6 Comparison of rear-end shapes [1]

The development of streamlined vehicles was interrupted by the Second World War. Despite the

success of modern streamlined vehicles, aerodynamics has only recently become a significant design

criterion. Aerodynamic development starts with the stylistic design. Details such as radii, curvature,

taper, spoilers etc are added to the initial shape, in combination, step by step, to prevent or control

separation (see appendix for info on Separation) so that the drag is minimized. Practice has shown

that in comparison to the initial shape significant reductions in the drag can be achieved in this

manner as shown in Fig. 1.7.

Fig.1.7 Design phases of a car shape [1]

Car manufacturers began to carry out aerodynamic development in their own purpose built wind

tunnels. The aerodynamicist became a dominant automobile engineer and had to interact with


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design. The stylist faced difficulties in designing the vehicle with aerodynamic demands, but soon

discovered that aerodynamics could set a more logical and reasonable trend than did fashion. Since

the trend was accepted as valid design criteria, car aerodynamics has progressed. [2]

Fig. 1.8 shows the change in shapes of the Porsche car models from 1950 to 1981. [1]

(A = frontal area, CD = coefficient of drag).

Large disciplines undergo major work and research in the field of aerodynamics. All car

manufacturers test their cars aerodynamics in some way. Their main aim was to reduce the drag

hence better aerodynamics.

Fig.1.9 shows the flow around a passenger car.


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Modern cars are characterized by streamlined forms. Wind tunnel tests have been carried out on

cars to observe the effects of automobile add-ons on the vehicles aerodynamics. It is necessary to

carry out wind tunnel tests in unstable conditions i.e. with crosswinds in addition to normal

atmospheric conditions. [5]

The aerodynamic characteristics of vehicles under cross winds depend not only on the shapes of the

vehicles but also on those of infrastructures [6]. Model testing is widely employed to predict

characteristics of vehicles with both external and internal flow of wind [7]. Wind tunnel tests were

made to evaluate the aerodynamic characteristics of typical configurations of cars on bridges under

wind directing:

- perpendicular to the vehicle

- relative to the vehicle.

- And for vehicles on embankments. [6]

The aim of these experiments was towards the safety of the vehicles passengers, and not so much

for the aerodynamic characteristics of the shape of the vehicle in terms of performance and fuel

efficiency which is why it is not totally relevant to the project.

The scale wind tunnel has been a principal development tool ever since aerodynamics has become

significant in automobile design. However, for true simulation of on-road conditions, the wind tunnel

has its own limitations. In a wind tunnel test, the ground is fixed relative to the vehicle, allowing a

boundary layer to develop. Also, the wheels of the vehicle do not rotate, and thus the drag of the

wheels is not taken into account. Aerodynamic data obtained from different wind tunnels show a

significant degree of scatter which may state that the tests are not as accurate as they have been

considered to be. [8]

Vehicles are never placed straight into a wind tunnel without enhancements. Usually, vehicles are

mounted on some sort of platform when tested in wind tunnels. The mount itself can cause

aerodynamic ‘disturbances’ such as turbulence leading to inaccuracy of results. The research into

building a magnetic levitation system has started in the field of Formula 1 racing cars. The

aerodynamics team at Durham University is attempting the use of Maglev (Magnetic levitation)

technology for scale wind tunnels. “The technology could significantly improve testing by eliminating

the interference caused by physical supports”. This technology has been attempted before by NASA

but with very limited success. In a real situation, on-road cars move through still air over a fixed

surface. However, during simulation in a wind tunnel, the car is held still while the air moves past.

So, to simulate the correct conditions, F1 teams make the ground under the car move, using a rolling

road. But then, the use of a moving belt means the model has to be supported by a

strut/beam/platform (usually from above) which interferes with the airflow around the vehicle and

thus reducing the accuracy of the experiment. This is why Durham researchers are developing a

maglev system to eliminate this interference; “which can have significant effects on the measured

drag and downforce”.

CFD technology is progressing to be more and more useful. But, “For predicting the aerodynamics of

the whole vehicle, computer simulations do not yet deliver the goods, Computer simulations are not

well validated, particularly for automotive work” [9].

Another method of experimentations is the use of Pressure Sensitive Paint abbreviated to PSP. The

use of PSP improves wind tunnel testing by reducing the amount of physical mechanical sensors

needed, which of course obstruct the flow around the mode. Also, the reduction of these

mechanical sensors reduces the cost of the experiments. However, PSP technology is developed

mainly for aircraft simulation, and they are accurate only at high speeds.


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Flow can be analyzed using then experimental method i.e. using a wind tunnel. And there is a

computational method using CFD software. And many times, they are both used in conjunction to

each other.

There are advantages of using CFD software over experimental methods such as wind tunnel testing.

A lot of aerodynamic testing is required in the field of Motorsport. Mainly for Formula 1, Le Mans

and Nascar racing.

The advantage of using CFD over wind tunnels is abundant. Using a computational method saves a

lot of time, money and effort. The results from computational testing are more informative than an

experimental result. Dimensional characteristics and surrounding characteristics can be changed

using mouse clicks and is very quick and effective. A computational method provides the ability to

conduct testing very early on in a programme. Engineers can make decisions in preliminary stages of

development rather than building a prototype, testing it and then making decisions. Because

computational software is entirely computational, a lot of cost is reduced because it is not

completely necessary to build a prototype before the testing is initiated. Prototypes can be built on

computational software and modified and tested without having to physically endure the operation.

The correlation between computational software and wind tunnel results is good; CFD is as accurate

as experimental wind tunnel testing. [10]

However, there are some drawbacks of using computational methods for aerodynamic testing. CFD

testing is quite complicated and requires some effort to get superior results. It requires many tweaks

to obtain the full potential of the software and its accuracy. There are still issues with prediction of

lift on a car with computational methods which is generally more difficult than the prediction of

drag. Also, the simulation of turbulence is not very accurate with Computational testing. [10]

CFD is commonly used in combination with scale-model and full-scale wind tunnels. For stock car

racing, Daimler Chrysler’s Dodge Division Aerodynamics team used computational methods in

combination with both scale and full-scale wind tunnel tests, and also in combination with on-track

testing. The reason for the use of scale models in wind tunnels in combination with computational

methods is because these tools are commonly used with commercial car design and testing.

Computational results are validated by comparing them to wind tunnel test results. The use of CFD

testing is necessary because it is very difficult to visualize the airflow streams under a ground vehicle

or under its hood during a wind tunnel test. [11]

The field of aerodynamics is vastly significant in the development of Grand Prix Cars. All the leading

teams of Formula 1 make use of wind tunnels almost continuously and the related cost of models,

tools and labour is colossal. F1 teams rely on wind tunnels significantly. The use of wind tunnels is far

more noteworthy than computational analysis for these disciplines. [12]

In 1999, the General Motors team proposed developed a new concept car with a significantly low

drag coefficient. Their PNGV (Partnership for a New Generation of Vehicles) project concept car had

a coefficient of drag, CD of 0.163. The aim for GM was to reduce drag by as much as possible and the

way to do this was by reducing turbulence. “Hold your hand out the window of a new car, and you

will get 20 fewer miles to the gallon”. By the end of 1997, a six person team including engineers,

aerodynamics and wind tunnel experts assembled for GM to start the PNGV project. Their aim was

to develop a sedan with an aerodynamically efficient shape. “The ideal aerodynamic shape is a

raindrop”. However, it wasn’t practical to force that shape upon a functional car body. Though,


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mounting the engine in the rear relieved some of this concern. The advantage of a rear mounted

engine is that it eliminates front air intakes and under body discharges, which in turn improves drag.

GM believed that Wind Tunnel testing proved more efficient than CFD analysis for checking drag. For

this reason, the team prominently used wind tunnels over computational analysis. However, the

team still used this method for a number of reasons. “CFD software was used as a diagnostic tool to

see how they could change surfaces and understand the consequences of those changes in

aerodynamic design”. However, their models needed wind tunnel tuning because there were many

details that simply could not be evaluated effectively using mathematical methods. [13]


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Chapter 2 Proposed Project Work

2.1 Project Aims The aim of this project is to perform flow measurement on 1/15th scale car shapes. The flow

measurement was carried out via two methods: experimental and numerical. Using knowledge of

aerodynamic theory acquired from a literature review, it was possible to conduct wind tunnel tests

on model car shapes and identify the flow characteristics around a typical car shape.

In order to perform experimental flow measurement, a test rig was designed and fabricated using

knowledge of materials and manufacture. The experimental data achieved was studied and

evaluated to identify the aerodynamic characteristics of the car.

This experimental data was compared with numerical data obtained through CFD study in order to

evaluate the flow characteristics and to verify the accuracy of the results.

2.2 Objectives Design and fabricate the test rig components to affix in the wind tunnel

Acquire theoretical knowledge about flow measurement using wind tunnel experiments and measurement systems

Design and fabricate 1:15th scale model car shapes

Conduct preliminary runs to check for functionality of the test rig

Make necessary improvements to optimize the test rig functionality

Conduct experimental analysis on model car shapes

Study numerical methods for flow measurements such as CFD

Use CFD software to conduct flow measurement on the car shapes

Compare the numerical results with the experimental results

Conclude and propose improvements for further study


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Chapter 3 Experimental Method:

3.1 Introduction. In order to conduct the experimentation, the wind tunnel would require some apparatus attached to

it. The apparatus must have precise dimensions and be made of suitable material in order to

conduct the experimentation in a smooth manner, and to achieve accurate results.

The experiment was carried out on scale model car shapes which were acquired. The scale of the

model car shape must be correct so that it fits in with the apparatus and the wind tunnel. For

detailed info on the fabrication of the test rig, see appendix.

The following figure shows the wind tunnel design:

Fig. 2.0 Wind tunnel

The dimensions of the test section inside the wind tunnel are 1000 x 300 x 300 mm.

3.2 Instruments.

3.2.1 Pitot Tube.

A Pitot tube connected to a manometer was used to measure the pressure inside the wind tunnel.

The experiment is to study the flow around different car shapes. To prevent complications in the

procedure, the flow was studied in 2 dimensions, an x-axis and a y-axis. Fig 2.1 shows the axis on the

wind tunnel chamber:

Fig.2.1 2-Dimensional measurement in a wind tunnel.

y-axis

x-axis


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The following diagram shows the points taken on a hatchback and their coordinates. Figure 2.3

shows the location of the points. For info on coordinates taken for the fastback, see appendix.

Point Coordinate (x,y)

(mm)

1 (330,0)

2 (290,70)

3 (250, 100)

3.5 (200,120)

4 (120,110)

5 (70,60)

6 (50,50)

6.5 (5,40)

7 (-10,0)

0 (370,0)

Table 1 List of coordinates.

Fig.2.3 Points on Hatchback.

To position the Pitot tube precisely so that it is possible to take readings along the Y axis, a height

gauge was used. The height gauge enables precise measurements to be taken along the y-axis.

Once the pressure readings are obtained, the velocity and resultant force can be calculated.

The measurement technique was based on Bernoulli’s principle, using the following equations:

Note: The coordinates were taken from a reference,

the reference is the point at the very front of the car in

contact with the floor.

The front of the car is located at 0mm and the rear at

321mm.

X=321 Fig.2.2 Two Dimensional Hatchback

X=0


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Total pressure (head), PTotal = PStatic + 𝛒𝐯𝟐

𝟐 --------------------------------Eq.1

PStatic = Static pressure

PDyn = ρV2/2 = Dynamic pressure

Integrating the pressures gives the resultant force, exerted by the relative motion of the air

(aerodynamic force, F) [15].

Using the calculated dynamic pressure, the air flow velocity can be calculated using the equation:

Air flow velocity, v = 𝟐×𝐏𝐃𝐲𝐧

𝛒 (in m/s)----------------------------------- Eq.2

Where,

ρ = air density in kg/m3 Note: varies with temperature, atmospheric pressure and humidity.

Pdyn = dynamic pressure in Pascals.

The Pitot-tube was used to measure static, dynamic and total pressure; however the instrument has

its own limitations. For detailed info on these limitations, see appendix.


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3.2.2 Accuracy of Total Head tube.

Before testing on a car shape in the wind tunnel, some preliminary measurements were taken to

verify the accuracy of the instruments.

The following diagram shows the total head readings from the copper total head tube compared

with readings from a Pitot Static tube:

Fig. 2.4 Total pressure readings

The results were taken in an empty wind tunnel with the following coordinates and air speed:

Coordinates are with reference to the front of the wind tunnel:

x coordinate: 500mm

y coordinate: 150mm

Air Speed: 8.5 m/s

As seen in the diagram above, the copper tube is as accurate as the pitot static tube for measuring

total head. However, this accuracy only exists for pressure readings within the central area of the

wind tunnel. At positions (along the y-axis) close to the bottom and top of the wind tunnel, the total

head tube gives erroneous results. The reason for these erroneous results are as follows:

- The entry point of the total head tube is much larger than that of the pitot static tube. This

large diameter means that the readings taken from the total head tube take into the account

pressure differences caused by boundary layers forming near the walls of the wind tunnel.

The following figure illustrates:

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

160.0

180.0

-1.2 -1 -0.8 -0.6 -0.4 -0.2 0

Hei

ght,

h (

mm

)

Total Head (mm of H2O)

Height against Total Head in an empty wind tunnel

Pitot Static Tube

Total Head Tube


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Low clearance for

total head tube

High clearance for

Pitot Static tube

Fig.2.5 A limitation of the Total Head tube

As seen in fig2.3 that the large entry point diameter of the total head tube allows the readings to

take into account the boundary layer caused near the walls (ceiling and floor) of the wind tunnel.

However, the boundary layers caused are not taken into account for the Pitot Static tube.


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3.2.3 Height gauge

Flow measurement was carried out at precise locations around the vehicle. To ensure precise

displacement of the Pitot tube along the y-axis, a height gauge was utilised. The height gauge was

placed on the external platform situated above the wind tunnel. The platform on which the car is

situated is used as the datum.

For detailed info about the height gauge, see appendix.

3.3 Car Shapes Three primary car designs were selected for flow measurement: Hatchback, Fastback and Saloon.

The rear end of these three car shapes is what particularly makes them distinct from one another.

These shapes are constructed in Solidworks and then manufactured out of foam. Foam is the

material choice for these car shapes because it is easily cut into distinct shapes, and it can be sanded

to generate smooth curves on the surface. The foam was cut into shape using a hot wire cutter

followed by a sanding process to ensure smooth curves.

The shapes are sketched in 2D, followed by extruding the shapes to form the car shape on

Solidworks. The following figures show the three shapes constructed and dimensioned using

Solidworks:

Fig2.6 Hatchback constructed in Solidworks


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Fig 2.7 Fastback constructed in Solidworks

Fig 2.8 Saloon constructed in Solidworks

In reality, the car would be supported by wheels at a certain height. In this analysis, the wheels of

the car are not taken into account. The reason being is that the study is conducted on the shape of

the car i.e. the car body rather than its accessories and attachments.


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The three shapes are based on three mass produced cars:

The hatchback being the 2002-2009 Ford Fiesta, the fastback being the Ford GT40 sports car. And

finally, the saloon is the Lincoln Town Car model. See appendix for images.

To ensure accuracy of the 2-Dimensional readings, measurements are taken at two locations along

the z-axis, and an average between the two is considered the correct reading. This practice

eliminates the chance of errors caused due to the position of measurement along the z-axis.

This is also to avoid recording results on the boundary wall sitting through the middle of the car, and

on the edges of the car [21].

3.4 Speed The wind tunnel is equipped with variable speed settings. Preliminary runs showed that at top speed

the wind tunnel undergoes extensive vibration causing the instruments to vibrate too. This situation

can potentially cause inaccuracy within the results.

So, the wind tunnel was operated on a slightly lower speed setting to prevent vibrations. The wind

tunnel was set at speed setting #4. Using the Pitot tube connected to an anemometer, the wind

speed was tested.

Wind speed setting #4: 8.5 m/s = 23.61 km/h

Top speed of wind tunnel: 14.5 m/s = 40.28 km/h

3.5 Number of Readings Several readings were taken to obtain a clear picture of the flow around a car, and to ensure

repeatability of the flow measurement. The three pressure components (total, dynamic and static

pressure) were taken at different height intervals at particular points along the x-axis. The y-axis

intervals are small closer to the surfaces and as the Pitot is moved away from the vehicle the

intervals are larger.


Paramesh Nirmal

07002348 25

3.6 Results Once the readings were taken, the results were analysed and enhanced. The pressure readings

require converting to standard units such as mm of H2O and N/m2. See appendix for conversion of

manometer readings. The results are stored in tabular form and analysed.

3.6.1 Static Pressure

The results show that the static pressure remains somewhat constant around the hatchback,

especially in the frontal region where there is minimum flow obstruction. There is no major

fluctuation in this pressure component. It is seen in Fig. 3.0 that the static pressure is fluctuating

however the fluctuation is minute, only between 2 mm of H2O.

Fig 2.9 Static Pressures measured on Hatchback

It is also noted from the experimental results that the static pressure is at it’s minumum value over

the roof of the vehicle in the central region.

0.0020.0040.0060.0080.00100.00120.00140.00160.00

-8.50 -8.00 -7.50 -7.00

Hei

ght,

h/m

m

Static Pressure (mm of H2O)

Height against Static Pressure on line 6.5 on Hatcback

0.0020.0040.0060.0080.00100.00120.00140.00160.00180.00

-4.50 -4.00 -3.50 -3.00 -2.50

Hei

ght,

h/m

m

Static Pressure (mm of H2O)

Height against Static Pressure on line 1 on (hatchback)


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85.00

95.00

105.00

115.00

125.00

135.00

145.00

155.00

165.00

2 4 6 8 10 12 14 16

Hei

ght,

h/m

m

fluid velocity, v / ms-1

Height against velocity on Hatchback

x coordinate 330

x coordinate 290

x coordinate 200

x coordinate 5

x coordinate 370

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00

Hei

ght,

h/m

m

fluid velocity, v / ms-1

Height against velocity on Hatchback

x coordinate 330

x coordinate 290

x coordinate 5

x coordinate 370

3.6.2 Velocity

The velocity is calculated using Eq. 2 stated earlier. The velocity calculated is the fluid velocity at the

point where the Pitot tube is placed.

The results show that the velocity increases when the area which it passes through decreases.

Fig 3.0 Experimental data of Fluid velocity around Hatchback in a wind tunnel (steady)

Fig 3.1 Experimental data of Fluid velocity around Hatchback in a wind tunnel (erroneous)


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Fig. 3.2 Points on Hatchback (reference for fig. 3.0 and 3.1)

As seen in figure 3.0 above, the fluid velocity is uniform at coordinates in the frontal region of the

car and the maximum velocity occurs at the top of the car (x-coordinate 200mm).

However, the data in figure 3.1 above shows that the velocity fluctuates extensively behind the car

(x-coordinates 290,330,370mm). The data representing velocities calculated in this is not very

reliable due to limitations of the instrument used. The fluid flow behind the car was expected to be

‘chaotic’ caused by recirculation of the fluid. As stated in the literature review, this recirculation is

the reason why the design of the rear end of the car is crucial for achieving improved aerodynamics.

At line 2 (x-coordinate 290mm), there is a lot of change in the velocity readings however, the

velocity stops fluctuating after reaching a certain height (95mm) and remains steady since. This

shows that only the velocity readings above a height of 85mm on line 2 can be considered reliable,

thereby the velocities below a height of 85mm are considered due to recirculation in that region. For

more info on recirculation see section 4.1 and 5.6.


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Chapter 4 Numerical Method:

4.1 Introduction The external airflow causes the largest amount of drag and handling instability for a car [20]. The

main difference in aerodynamics between cars is due to the vehicle’s rear. As the air flows over the

roof of the vehicle, some of the air drops to zero velocity due to friction. A velocity profile starts

close to the vehicle surface and this is known as the ‘boundary layer’. Where the boundary layer

detaches from the car body is known as the ‘separation point’. The boundary layer detaches from

the vehicle roof and continues to flow in a straight line. As it flows, it tries to remove air from behind

the vehicle, causing a pressure drop or drag [1]. By numerical testing methods, this pressure drop

and low velocity region at the rear of the car was inspected.

Implementing numerical flow measurement around car shapes involves the employment of CFD

software.

A model was built in CFD (FLUENT 12.0), which represents a system that can be subjected to a

number of simulations. Fluid Physics can predict how fluid will act in a pipe or heat through different

surfaces. [20]

Fig.3.3 Total Pressure contours in FLUENT

4.2 Fluent Results

4.2.1 x-velocity

This is the x component of the velocity vector encountered by the vehicle due to the air flow against

it. This velocity is at its maximum value at the top of the car, and at the top of the windscreen of the

car. In FLUENT, this area of high velocity is denoted by the colour red and blue for low velocity [21].


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4.2.2 Static Pressure

This is the pressure exerted on the car body in the y-direction. Maximum static pressure occurs at

the front face of the car and is denoted by the colour red in FLUENT, and low static pressure is

denoted by the colour blue [21].

4.2.3 Turbulence intensity

Turbulence intensity is the level of turbulent flow. Turbulent flow is measured by chaotic fluid flow

changes. The flow is expected to be characterized by low turbulence intensity:

Flow originating from a fluid that stands still, like external flow across cars, submarines and aircrafts.

Very high-quality wind-tunnels can also reach really low turbulence levels. Typically the turbulence

intensity is very low, well below 1% [22].

4.3 Two dimensional mesh set-up using ICEM CFD A ‘virtual’ wind tunnel was created using this particular software, then transferred to FLUENT to

analyse flow measurement. The virtual wind tunnel was created as an exact replica of the wind

tunnel used for experimental flow measurement. Hence, the dimensions of this 2-D wind tunnel

were 1000 x 300 x 300 mm. The geometry of the wind tunnel is shown in section 3.

The car body and the wind tunnel were meshed using a hexagonal (hexa-dominant) mesh on ICEM

CFD to a surface. The surface was created using explicit coordinates, using the front of the car as the

reference point. A fine mesh was used so that the resultant change in velocity and pressure at

minute height intervals can be noted. The mesh size was set to be variable between 1-2 mm.

Based on the available research, one of the most vital areas of interest in vehicle aerodynamics is the

‘wake’ region created behind the vehicle as air passes over it, causing recirculation [13].

During experimental analysis, the vehicle was positioned on a platform which was at a certain height

above the wind tunnel. This platform was not constructed using CFD setup for the following reasons:

- When carrying out 2-D flow measurement on CFD, the software assumes the legs of the

platform as an obstruction to the air flow. In reality, this is not true.

Fig.3.4 Attempt to elevate car on a platform on CFD.

The car shape was positioned on a platform during experimental testing in a wind tunnel, meaning

the car was slightly elevated above the bottom of the wind tunnel (by 130mm). This means that the


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07002348 30

distance from the top of the car to the top of the wind tunnel is 50mm. To ensure that this situation

is simulated in FLUENT, the dimensions of the wind tunnel were modified for numerical analysis. The

height of the wind tunnel is changed from 300mm to 170mm in ICEM CFD and then transferred to

FLUENT.

To run a simulation, the boundary conditions need to be set so that when the mesh is transferred to

FLUENT they can be assigned certain characteristics. The walls of the wind tunnel are labelled in

ICEM so that they can be utilised to set boundary conditions in FLUENT. For example, the inlet vent

of the wind tunnel is labelled as inlet on ICEM so that it is recognised in FLUENT as the flow inlet. The

case is similar for the ceiling, floor and outlet vent of the wind tunnel so that the boundary

conditions can be set accordingly.

Fig. 3.5 Hatchback mesh setup

Fig. 3.6 Fine Mesh

321mm


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4.4 Two dimensional analysis in FLUENT

4.4.1 Boundary Conditions

Once the mesh has been transferred from ICEM CFD to FLUENT 12.0, the boundary conditions are to

be allocated. The front of the wind tunnel is defined as inlet with an air inlet speed of 8.5 m/s. The

rear of the wind tunnel is defined as outflow. The top and bottom of the wind tunnel are walls.

These boundary conditions make the virtual wind tunnel a close replication of the wind tunnel set up

during experimental testing.

The air flowing over the model was investigated as Turbulent flow using the K-Epsilon turbulence

model.

Fig. 3.7 Defining boundary conditions

1. Inlet – Velocity inlet

2. Outlet – Outflow

3. Top – Wall

4. Bottom 1 – Symmetry

5. Bottom 2 - Symmetry

1

3

4 5

2


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Chapter 5 Results and Discussion

5.1 Introduction The results discussed in this section are from both, experimental testing and numerical testing. Both

data are results from 2-Dimensional analysis. The investigation has been carried out at low speed

(8.5 ms-1).

Around 20 sets of data for each position along the x-direction are taken, although, the size of the

sets of data depend on the height of the plane along the y-axis. There are 5 points along the x-axis

when taking measurements around the hatchback, totalling to roughly 100 sets of data taken

experimentally for the one car shape. Similar numbers of data sets are to be extracted from the

numerical results, making sure that the (x,y) coordinates for the numerical data matches exactly with

the (x,y) coordinates for the experimental data.

The data from FLUENT was extracted using the lines/rakes feature. Lines with the same coordinates

and dimensions as used during experimental testing were created in FLUENT and the data values

along these lines were extracted. Using the software’s post-processing feature, the data was

exported into Microsoft Excel.


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Turbulent Flow

Line 3.5 on Hatchback

x-coordinate = 200mm

Wind Tunnel Speed, u0= 8.5 ms-1

Height above base

(a)

Velocity (Experimental

results), v (b)

Velocity (FLUENT

results), u (b)

pressure coefficient

(static) experimental,

cp.exp (c)

pressure coefficient

(static) FLUENT,

cp.cfd (c)

0.3738 1.0140 0.9869 -0.0013 0.0006

0.3894 1.0067 0.9869 0.0060 0.0006

0.4050 1.0033 1.0148 0.0495 0.0244

0.4206 0.9920 1.0163 0.0786 0.0508

0.4361 0.9813 1.0153 0.1004 0.0735

0.4517 0.9700 1.0141 0.1294 0.1016

0.4673 0.9587 1.0139 0.1440 0.1167

0.4829 0.9473 1.0147 0.1585 0.1346

0.4984 0.9320 1.0157 0.1803 0.1433

(a) Non dimensional height = height/length of car = h/321 mm

(b) Non dimensional velocity = velocity/velocity at reference point

(c) Cp = p−pref

1

2𝜌 .(𝑢𝑟𝑒𝑓 )2

Where pref.exp = -143Pa, pref.CFD= -765Pa, uref.exp = 15ms-1, uref.CFD = 32ms-1

Table 2 Velocity and Static Pressure Readings for Line 3.5 on Hatchback

Line 3.5


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07002348 34

Turbulent Flow

Line 0 on Hatchback

x-coordinate = 370 mm


height (y)

Dyamic head

reading

Dynamic Head mm of H2O (x

0.1)

Dynamic Head, PD (N/m2)

0.0000 -16.0000 -1.6000 -15.6906

5.0000 -16.0000 -1.6000 -15.6906

10.0000 -16.0000 -1.6000 -15.6906

15.0000 -15.0000 -1.5000 -14.7100

20.0000 -15.0000 -1.5000 -14.7100

30.0000 -14.0000 -1.4000 -13.7293

40.0000 -10.0000 -1.0000 -9.8067

50.0000 -5.0000 -0.5000 -4.9033

60.0000 23.0000 2.3000 22.5553

70.0000 69.0000 6.9000 67.6659

80.0000 85.0000 8.5000 83.3565

90.0000 88.0000 8.8000 86.2985

100.0000 95.0000 9.5000 93.1632

120.0000 98.0000 9.8000 96.1052

140.0000 95.0000 9.5000 93.1632

160.0000 79.0000 7.9000 77.4725

Table 3 Dynamic Head at Rear of Car (experimental results).

Line 0


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5.2 Velocity As stated in Chapter 3, maximum velocity occurs at the top of the car, in the central region. This is

due to the decrease in area that the air has to flow through. This is the case for both, experimental

results and FLUENT results. The following figure illustrates that the central region over the roof of

the vehicle is the region of maximum velocity (highlighted by the colour red).

Fig. 3.9 x-velocity contours on hatchback.

The following discussion concerns the results from Table 2.

The experimental results obtained from this region can be considered reliable because the air

predominantly flows in one direction only, the x-direction. Fig. 4.0 shows the comparison of the

experimental results with CFD results. Both results are similar as both velocities are moderately

steady and at their maximum value in this region. The similarity in the results is because the Pitot

tube is reliable for measuring pressure where the fluid flow is in one direction.

Max Velocity


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07002348 36

Fig.4.0 Height vs. Velocity (Line 3.5 on Hatchback).

0.40

0.42

0.44

0.46

0.48

0.50

0.52

0.00 0.20 0.40 0.60 0.80 1.00 1.20

h /

l

Velocity/u0

Height vs. Velocity (Line 3.5 on Hatchback)

experimental

fluent


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07002348 37

5.3 Static Pressure (ps) As stated in Chapter 3, it can be seen that the static pressure is at its minimum value over the roof of

the vehicle from the experimental data obtained. The case is the same with the FLUENT results (see

Fig.4.1).

Fig. 4.1 Contours of Static Pressure for the hatchback on FLUENT

The following discussion concerns the results from Table 2.

As well as the velocity measurements, the static pressure measurements are considered trustworthy

because the Pitot tube is reliable for taking measurements where there is no recirculation/negative

velocity. As seen in Table 2, the Static Pressure coefficient obtained from experimental results

correlates with the static pressure obtained from CFD analysis in FLUENT (see Fig. 4.2).

0.00

0.10

0.20

0.30

0.40

0.50

0.60

-0.05 0.00 0.05 0.10 0.15 0.20

h /

l

Static Pressure Coefficient, cp

Height vs Static Pressure (Point 3.5 on Hatchback)

Experimental

FLUENT

Fig.4.2 Height vs. Static Pressure on Hatchback


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07002348 38

Maximum static pressure occurs at the front of the car. This is shown in Fig. 4.1, the area in front of

the vehicle consists of high static pressure. Previous experiments also show the same case [21]. This

significantly high static pressure can be attributed to the front face of the vehicle’s poor curvature

and high projected area [25].

5.4 Rear End As mentioned earlier, the results obtained from experimental results are erroneous at points behind

the vehicle. This is the region where the pressure drops and recirculation occurs [4] [8]. These

incorrect readings exist in the data obtained for dynamic pressure, velocity and total pressure. See

Fig. 4.3 for recirculation velocities at the rear end of the vehicle.

Fig. 4.3 x-velocity vectors at rear end of Hatchback

This recirculation occurring at the rear of the vehicle is the result of airflow from the car roof causing

vortices to form [21]. As seen in Fig. 4.3, the velocity vectors show that the air is undergoing

recirculation in this region. The air velocity is at its minimum in this region, this is also shown from

the experimental results (see appendix).

The air velocity is negative in this region, which may be due to increased mixing of the air flow due

to turbulence (see Fig.4.4) [21]. The velocities obtained in this region from experimental results may

well be negative because of the fact that the dynamic pressure in this region is a negative number as

seen in Table 2. However, the velocity is calculated using Bernoulli’s equation (eq.2) [15]:

PDyn = ρV2/2 = Dynamic pressure


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07002348 39

=> Air flow velocity, v = 𝟐×𝐏𝐃𝐲𝐧

𝛒

The air flow velocity is the square root of the dynamic pressure meaning the velocity cannot be a

negative number as it is not possible to square root a negative number. Therefore, the velocity is

calculated using the following equation (eq.3), where the velocity is the square root of the modulus

of the dynamic pressure, thus giving a positive velocity. This case is the same for all velocities

calculated in the experimental results.

Equation.3.0:

Air flow velocity, v = 𝟐×|𝐏𝐃𝐲𝐧|

𝛒

Fig.4.4 Contours of Turbulent Intensity on Hatchback

Shown in figure 4.4 above, the region behind the car is intensely turbulent. This turbulence causes

the negative pressure behind the car, resulting in recirculation of air flow.

As stated in the previous page, the experimental readings behind the car are erroneous. This is due

to the limitations of the Pitot tube. The Pitot tube only measures pressure in a single direction

meaning areas where flow is occurring in several directions cannot be investigated using just a Pitot

tube.

The negative dynamic pressure obtained in the recirculation region means that the pressure is acting

in the opposite direction i.e. against the direction of the flow. To check for this, the Pitot tube was

placed facing the rear of the wind tunnel at point 0. The data obtained for a rear facing Pitot tube

was erroneous too, however, it was noted that the Static pressure remains unaffected by the change

in direction of the Pitot tube. This is because static pressure is the pressure exerted by the fluid


Paramesh Nirmal

07002348 40

when static [24] therefore, static pressure acts in one direction only, the y-direction. See table 4 and

Figure 4.5 for static pressure readings for Pitot tube facing the front and rear of the wind tunnel.

Fig.4.5 Height vs. Static Pressure for Pitot tube placed in opposite directions (Line 0 on Hatchback).

The above graph is related to the data in Table 4 in the next page.

0.00

0.10

0.20

0.30

0.40

0.50

0.60

-1.0 0.0 1.0 2.0 3.0 4.0

h /

l

Static Pressure coefficient, cp

Height vs. Static Pressure (Line 0 on Hatchback)

Pitot facing the rear

Pitot facing the front


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07002348 41

Turbulent Flow

Line 0 on Hatchback

x-coordinate = 370 mm


Height, mm

(a)

Static

Pressure

coefficient

(Pitot facing

rear)

(b)

Static Pressure

coefficient (Pitot facing

front) (b)

0.0000 0.0829 0.0829

0.0156 0.2136 0.2136

0.0312 0.0175 0.0175

0.0467 -0.1787 -0.3094

0.0623 -0.3094 -0.3094

0.0935 -0.0479 -0.1787

0.1246 -0.3094 -0.3094

0.1558 -0.5709 -0.5709

0.1869 -0.5055 -0.5055

0.2181 -0.4402 -0.5055

0.2492 -0.1787 -0.1787

0.2804 0.0829 0.0829

0.3115 0.4097 0.3444

0.3738 2.4365 2.3711

0.4361 2.5018 2.6326

0.4984 2.7633 3.0249

Table 4 Static Pressure at Line 0 on Hatchback (experimental results).

(a) Non dimensional height =

height/length of car = h/321

mm

(b) Cp = p−pref

1

2𝜌 .(𝑢𝑟𝑒𝑓 )2

Where pref.= -115Pa, uref =

5ms-1

Line 0


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07002348 42

5.5 Saloon and Fastback

5.5.1 Saloon

In comparison to the Hatchback, CFD results show that the Saloon shape undergoes fairly low

turbulence. The turbulent intensity around the saloon shape only persists behind the car in the rear

region, causing negative x-velocities thus resulting in recirculation of the air flow. The saloon shape

also experiences high turbulent intensity over its roof. This may be due to the formation of a

boundary layer over the top of the car.

Fig. 4.6 Turbulent Intensity contours around a saloon shape

Similar to the hatchback, the saloon shape experiences maximum static pressure on its front face.

However, unlike the hatchback, minimum static pressure does not occur over the roof of the car.

This may be due to the shorter height of the saloon in comparison to the hatchback. This shorter

height increases the distance from the roof of the car to the top of the wind tunnel, allowing the air

to flow over the car through a larger volume.


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07002348 43

Fig. 4.7 Contours of static pressure around a saloon shape

5.5.2 Fastback

Out of the three shapes, the fastback is expected to be the most ‘streamlined’ shape. The fastback is

a type of sports car shape, the car having a low height and the shape being similar to the teardrop

shape, making it more aerodynamically efficient [2].

Similar to the saloon shape, the fastback experiences high turbulent intensities over the roof of the

car. This again may be due to the development of a boundary layer. The case is the same for the

area of maximum static pressure around the fastback (see Fig. 5.0).

Fig.4.8 Contours of turbulent intensity around a fastback shape


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07002348 44

Fig. 4.9 Contours of Static pressure around a fastback shape

Fig. 5.0 x-velocity vectors in rear region of fastback shape


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07002348 45

5.6 Recirculation Length (RL) Recirculation occurs at the rear of the vehicle due to the airflow over the car roof leading to a

sudden expansion in area the air flows through. This expansion causes a vortex to form in this newly

expanded area. The recirculation affects the drag at the rear of the vehicle. To reduce recirculation,

the rear of the car is modified to allow the trailing air vortices to merge smoothly and avoid the

sudden increase in rear area. The teardrop shape mentioned in the literature review is the perfect

aerodynamic shape where the air vortices merge smoothly [15]. However, a teardrop shape is

impractical in many ways.

The car models were analysed at quicker speeds during this part of the analysis:

70 mph = 31.29 m/s

50 mph = 22.35 m/s

In order to calculate the recirculation length, the line/rake function in FLUENT was utilised. A

horizontal line was created behind each car passing through the vortex of recirculation. The distance

(x coordinate) against velocity on this line is plotted. The recirculation length is defined as the length

of negative x-velocity.

Fig. 5.1 Turbulent Recirculation length (Hatchback)

-0.35

-0.30

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0.98 1.03 1.08 1.13 1.18 1.23

velo

city

, u/u

0

RL (distance / length of car)

Recirculation length vs. x-velocity for Hatchback

70mph

50mph


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07002348 46

Fig. 5.2 Turbulent Recirculation length (Fastback)

The length of recirculation does not change with respect to speed for the Hatchback and the

Fastback.

RL for Hatchback: 0.257

RL for Fastback: 0.154

However, there is a major change in RL with respect to speed for the Saloon shape. The following

figure shows:

Fig. 5.3 Turbulent Recirculation length (Saloon)

As seen in the figure above, the recirculation length of the saloon is 0.173 when u0=70mph and just

0.148 at 50mph. The RL has reduced by 0.025. This change is RL is only seen with flow around the

Saloon and not with the fastback and hatchback due to the shape of the vehicle. The saloon has a

-0.14

-0.12

-0.10

-0.08

-0.06

-0.04

-0.02

0.00

1.15 1.20 1.25 1.30 1.35

velo

city

, u/u

0


Recirculation length vs. x-velocity for Fastback

70mph

50mph

-0.35

-0.30

-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0.90 0.95 1.00 1.05 1.10 1.15

velo

city

, u/u

0


Recirculation length vs. x-velocity for Saloon

70mph

50mph


Paramesh Nirmal

07002348 47

‘notch’ at the rear end; this notch is there for practicality, giving the car more ‘boot space’. However,

this notch creates turbulence at the rear end (see fig. 5.4).

Fig. 5.4 Turbulent intensity at rear region of Saloon.

The fastback shape is based on the teardrop shape, its smooth sloping rear, and the spoiler attached

to the rear allows the air to flow smoothly through the newly expanded region behind the car.

Fig.5.4 shows the recirculation around the fastbacks rear.


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07002348 48

Chapter 6 Conclusion

The aim of the investigation was to carry out flow measurement around typical car shapes using

experimental and numerical methods. The result of the investigation states:

The airflow around vehicles causes a low pressure region behind the vehicle. This low

pressure region causes negative x-velocities resulting in recirculation of the air. The main

reason to this is the turbulence caused. All three shapes undergo turbulent flow of air

around them; the negative pressure region is the effect of this turbulence.

The fastback is the most aerodynamic shape because there is least turbulence around the

vehicle.

The Pitot tube is reliant for carrying out flow measurement around shapes however; it is

only valid for areas where the air is flowing ‘smoothly’ in one direction.

The Pitot tube is incapable of providing true values of pressure and velocity in the region

behind the vehicles.

The vast difference between the experimental results and numerical results at the rear end

of the car is due to these limitations the Pitot tube has with flow measurement around car

shapes.

It is possible to use a total pressure tube to measure total pressure at places incapable of the

Pitot tube to reach. However, the total pressure tube cannot measure velocity or static

pressure.

Maximum static pressure occurs at the front face of the car due to the large area for the air

to act upon, minimum static pressure occurs above the car roof.

Maximum x-velocity occurs above the car roof due to the small area between the top of the

car and the top of the wind tunnel which the air flows through.

The height gauge has proved to be a very useful instrument to be used when carrying flow

measurement of such scale in a wind tunnel.

At regions where the flow is stagnant and undisturbed, the experimental results correlate

with the CFD results.

The main factor in improving car aerodynamics is the shape of the vehicles rear end.

At such low speeds (8.5 m/s) it was not copiously possible to perceive all differences

between the three car shapes, and not possible to carry out a full analysis of flow around the

vehicles.

CFD results can be considered very reliable, and CFD has the capability to analyse flow

around car shapes with intricate detail, even with such low speeds.

Because the wind tunnel had a low maximum speed (12.5 m/s), it was not possible to carry

out a full analysis of flow around the car shapes. Even when the wind tunnel as operating at

full speed, the vibrations caused inaccuracy in results thus, the wind tunnel was operated at

lower speed, 8.5 m/s.


Paramesh Nirmal

07002348 49

Chapter 7 Recommendation for further studies

Due to time constraints with this project, a full flow analysis was not accomplished. With available

time, other instruments could be used to investigate the flow around a car in the future. Instead of a

Pitot tube, a hot wire can be used to investigate flow in 3 dimensions. If flow is analyzed in 3

dimensions, it is possible to investigate the effects of accessories such as wing mirrors, spoilers, etc

to a vehicle’s aerodynamics. Also, 3D flow measurements will provide a clearer understanding of the

aerodynamics of road vehicles and a better, thorough analysis can be carried out. Other instruments

such as pressure-sensitive paint can be used to analyze the effects of flow around a car.

If a high speed tunnel can be employed, the flow around the car shapes can be investigated in more

realistic situations, where aerodynamics is crucial. More different car shapes can be analyzed with

more time, giving chance to analyze the design of vehicles. These may include estates, jeeps, vans,

even buses or trucks.

The force on the car was not analyzed in this project. A sensitive scale or balance may be used to

measure the drag force and lifts on a car shape.

Using more detailed shapes can provide a better understanding of flow around the shapes. This may

include shapes with wheels so the air passing under the car shape can be applied to make the

investigation more thorough.

A moving floor can be used with both experimental and numerical testing. The moving floor can

provide a better understanding of the aerodynamics of a car in a real life situation.


Paramesh Nirmal

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References ___________________________________________________________________________

1. Hucho, W.-H., Introduction to automobile aerodynamics, in Aerodyamics of road

vehicles W.-H. Hucho, Editor. 1987, Butterworths. p. 1 - 36

2. Necati, G.A., Measurement and test techniques, in Aerodynamics of Road Vehicles,

W.-H. Hucho, Editor. 1987, Butterworths. p. 437-478

3. Pope, A. and J.J. Harper, Instrumentation and Calibration of Test Section, in Low-

Speed Wind Tunnel Testing. 1966, John Wiley & Sons. p. 85-125

4. Pankhurst, R.C. and D.W. Holder, Measurement of Fluid Velocity, in Wind-Tunnel

Technique. 1965, Pitman & Sons LTD. p. 176-225

5. Watkins, S. and G. Oswald, The flow field of automobile add-ons - with particular

reference to the vibration of external mirrors. Journal of Wind Engineering and

Industrial Aerodyanmics, 1999. 83: p. 541-554

6. Suzuki, M., K. Tanemoto, and T. Maeda, Aerodynamic characteristics of

train/vehicles under cross winds. Journal of Wind Engineering and Industrial

Aerodyanmics, 2003. 91: p. 209-218

7. Nakayama, Y. and R. Boucher, Measurement Technique, in Introduction to Fluid

Mechanics. 1998, Butterworth-Heinemann.

8. Bischof, G., et al., On-road determination of aerodynamic drag improvements.

Automotive Engineering, Institute of Mechanical Engineering (IMechE) Proceedings

D, 2004. 1-6(218): p. 1-5

9. Knight, H., Wind of Change. Engineer, 2005. 293(7677): p. 30-33

10. Slavnich, D., Quick, quick flow. Automotive Engineering, 2002. 27(6): p. 46-53

11. Thilmany, J., Design like the Wind. Mechanical Engineering, 2004. 126(7): p. 12

12. Dominy, R.G., Aerodynamics of Grand Prix Cars. Automotive Engineering, Institute

of Mechanical Engineering (IMechE) Proceedings D, 1992(206): p. 267, 268

13. Sharke, P., Smooth Body. Mechanical Engineering, 1999. 121(10): p. 74-77

14. Klein, C., Application of Pressure Sensitive Paint (PSP) for the determination of the

instantaneous pressure field of models in a wind tunnel. Aerospace Science and

Technology, 2000. 4(2): p. 103-109


Paramesh Nirmal

07002348 51

15. Scibor-Rylski, A.J., Introduction, Aerodynamic Forces and Moments, in Road Vehicle

Aerodyanmics. 1975, Pentech Press. p. 1-12

16. Ashby, M.F., Engineering Materials and their properties in Materials Selection in

Mechanical Design, 3rd

Edition, 2005 p. 27-44

17. CES Edupack Selector Version 5.1.0.

18. Doebelin, E., Measuring Devices, in Measurement Systems: Application and Design

1983. p 492 - 296.

19. Physics Forums, Mechanical Engineering Questions, www.physicsforums.com

Accessed 03-11-09

20. FLUENT – What is CFD?

www.fluent.com/solutions/whatcfd.html Accessed 03-11-09

21. March S., Numerical investigation of flow fields over three dimensional car shapes

2006. p. 9-12

22. Turbulence Intensity, Estimating the Turbulence Intensity – www.cfd-online.com

Accessed 05-11-09

23. Hucho, W.-H., Some fundamentals of fluid mechanics, in Aerodyamics of road

vehicles W.-H. Hucho, Editor. 1987, Butterworths. p. 55

24. wiseGeek,

What is Static Pressure?

http://www.wisegeek.com/what-is-static-pressure.htm Accessed 03-03-10

25. Chainani A. Perera N., CFD Investigation of Airflow on a Model Radio Control Race

Car. World Congress on Engineering Proceedings, 2008 Vol II p. 2-4

http://www.physicsforums.com/

http://www.fluent.com/solutions/whatcfd.html

http://www.cfd-online.com/

http://www.wisegeek.com/what-is-static-pressure.htm


Paramesh Nirmal

07002348 52

Bibliography Hucho, W.-H., Introduction to automobile aerodynamics, in Aerodyamics of road

vehicles W.-H. Hucho, Editor. 1987, Butterworths. p. 1 - 36

Necati, G.A., Measurement and test techniques, in Aerodynamics of Road Vehicles, W.-

H. Hucho, Editor. 1987, Butterworths. p. 437-478

Pope, A. and J.J. Harper, Instrumentation and Calibration of Test Section, in Low-Speed

Wind Tunnel Testing. 1966, John Wiley & Sons. p. 85-125

Pankhurst, R.C. and D.W. Holder, Measurement of Fluid Velocity, in Wind-Tunnel

Technique. 1965, Pitman & Sons LTD. p. 176-225

Watkins, S. and G. Oswald, The flow field of automobile add-ons - with particular

reference to the vibration of external mirrors. Journal of Wind Engineering and Industrial

Aerodyanmics, 1999. 83: p. 541-554

Suzuki, M., K. Tanemoto, and T. Maeda, Aerodynamic characteristics of train/vehicles

under cross winds. Journal of Wind Engineering and Industrial Aerodyanmics, 2003. 91:

p. 209-218

Nakayama, Y. and R. Boucher, Measurement Technique, in Introduction to Fluid

Mechanics. 1998, Butterworth-Heinemann.

Bischof, G., et al., On-road determination of aerodynamic drag improvements.

Automotive Engineering, Institute of Mechanical Engineering (IMechE) Proceedings D,

2004. 1-6(218): p. 1-5

Knight, H., Wind of Change. Engineer, 2005. 293(7677): p. 30-33

Slavnich, D., Quick, quick flow. Automotive Engineering, 2002. 27(6): p. 46-53

Thilmany, J., Design like the Wind. Mechanical Engineering, 2004. 126(7): p. 12

Dominy, R.G., Aerodynamics of Grand Prix Cars. Automotive Engineering, Institute of

Mechanical Engineering (IMechE) Proceedings D, 1992(206): p. 267, 268

Sharke, P., Smooth Body. Mechanical Engineering, 1999. 121(10): p. 74-77

Klein, C., Application of Pressure Sensitive Paint (PSP) for the determination of the

instantaneous pressure field of models in a wind tunnel. Aerospace Science and

Technology, 2000. 4(2): p. 103-109

Scibor-Rylski, A.J., Introduction, Aerodynamic Forces and Moments, in Road Vehicle

Aerodyanmics. 1975, Pentech Press. p. 1-12


Paramesh Nirmal

07002348 53

Ashby, M.F., Engineering Materials and their properties in Materials Selection in

Mechanical Design, 3rd

Edition, 2005 p. 27-44

CES Edupack Selector Version 5.1.0.

Doebelin, E., Measuring Devices, in Measurement Systems: Application and Design

1983. p 492 - 296.

Physics Forums, Mechanical Engineering Questions, www.physicsforums.com

Accessed 03-11-09

FLUENT – What is CFD?

www.fluent.com/solutions/whatcfd.html Accessed 03-11-09

March S., Numerical investigation of flow fields over three dimensional car shapes 2006.

p. 9-12

Turbulence Intensity, Estimating the Turbulence Intensity – www.cfd-online.com

Accessed 05-11-09

Hucho, W.-H., Some fundamentals of fluid mechanics, in Aerodyamics of road vehicles

W.-H. Hucho, Editor. 1987, Butterworths. p. 55

wiseGeek,

What is Static Pressure?

http://www.wisegeek.com/what-is-static-pressure.htm Accessed 03-03-10

Chainani A. Perera N., CFD Investigation of Airflow on a Model Radio Control Race

Car. World Congress on Engineering Proceedings, 2008 Vol II p. 2-4

Car Images: www.desktopmachine.com

http://www.physicsforums.com/

http://www.fluent.com/solutions/whatcfd.html

http://www.cfd-online.com/

http://www.wisegeek.com/what-is-static-pressure.htm

http://www.desktopmachine.com/


Paramesh Nirmal

07002348 54

Chapter 8 Appendix:

8.1 Separation: Laminar and turbulent boundary layer flows depend strongly on pressure distribution which

is imposed by the external flow. For a pressure increase in low direction the boundary layer

flow is retarded, especially near the wall, and even reversed flow may occur. This is known

as flow separation. [23]

8.2 Design of experimental components: The components to be designed are:

- Internal Platform

The internal platform was placed inside the wind tunnel. The model car shapes was placed

on this platform during experimentation.

- Lid

The lid will have various holes drilled into it. When taking measurements of pressure, the

Pitot tube was inserted into the platform through these holes. The purpose of the lid is to

ensure that very little air escapes the wind tunnel through the top. The experiment could be

conducted without using a lid and just inserting the Pitot tube through the top. However,

not using a lid means plenty of air will escape through the top thus disrupting the flow

leading to inaccuracy of results.

- External Platform

The external platform was held above the wind tunnel chamber either using stands and

clamps or by building a new stand. The purpose of the external platform is to allow

instruments such as the height gauge to be placed in a suitable position (above the wind

tunnel).

- Dowels

Dowels was used to hold the internal platform at a certain height above the bottom of the

wind tunnel (See fig 5.5).

Fig: 5.5 holes to place dowels

The dowels will securely fit the holes on the internal platform and the holes at the bottom

of the wind tunnel, creating an elevated platform inside the chamber.

Holes to insert dowels

and secure the internal

platform into place

Bottom of wind tunnel

Top of wind tunnel


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- Plugs

The holes in the lid will require plugs so that when holes are not in use they are plugged

shut to ensure no losses.

8.3 Design the Test Rig.

The wind tunnel chamber is 1m long x 0.3 m high x 0.3m deep (see fig. 5.6).

Fig 5.6 Wind Tunnel Chamber

The apparatus was designed so that it fits with the above chamber.

8.4 Choosing correct Material. 8.4.1 Material Properties.

The optimum material to use to build the components must have the following mechanical

properties: Electrical and thermal properties are non-applicable.

Wood is a suitable material to build the components required for this experiment. Metals

consist of the above properties however, a metal for example aluminium; it is not as easy to

machine aluminium into the shape required as it is with wood. Because the thickness of the

platform is high (10mm), it is much more straightforward to machine a piece of wood which

is 10mm thick than it is to machine a piece of metal 10mm thick.

8.4.2 Chosen Materials.

The platforms was built from MDF because MDF consists of the optimum mechanical

properties required, and it is very cheap. The lid will also be made from MDF because of its

dimensions.

The dowels was built from balsa wood because of their shape. Balsa wood is a hardwood,


Paramesh Nirmal

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but it is also very soft. It has the mechanical properties of a hardwood so dowels made from

balsa wood will withstand the load of the internal platform with ease.

The plugs will also be built from balsa wood because of their cylindrical shape, and the

mechanical properties of balsa wood.

8.5 Building the components.

The platforms and the lid were built by means of machining. Sheets of MDF were machined

to the correct dimensions using an electric saw.

To avoid turbulence near the front of the vehicle, the internal platform was sanded until it

characterized a smooth, streamlined shape (See Fig 5.7)

Fig 5.7 Non-streamlined platform

If the internal platform wasn’t smoothened to a streamlined shape, turbulence will occur at

the front of the car when testing in the wind tunnel, which can disrupt the results.

Once the platform is ‘streamlined’, the air will flow underneath the platform in laminar

fashion, preventing turbulence at the front of the car (see Fig 5.8)

Fig 5.8 Streamlined platform

The figure shows how the air passes through the bottom of the platform rather than a

turbulent flow near the front of the car.


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8.6 Assembling the components.

Prior to the experiment, the components must be attached to the wind tunnel.

Fig 5.9 shows the platforms attached to the wind tunnel. The external platform is attached

using a stand and a clamp on either side. The internal platform is attached using dowels.

Fig. 5.9 Wind tunnel apparatus

8.7 Total Pressure Tube: Copper is the optimum material to make a total pressure tube because it is very ductile and

malleable. Due to copper’s high ductility, a copper tube can be bent 90 degrees without any

sort of failure (such as dents or cracks).

A general rule of thumb is that the diameter of the tube must be 1/4 – 1/8 the size of the

bend [19]


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8.8 Manometer setting:

The manometer has 3 inclination settings. The angle of inclination affects the reading given

by the manometer. If the manometer was placed vertically, the reading given by the

manometer would not require scaling. However, when inclined, the reading given by the

manometer requires scaling depending on the inclination.

Fig.6.0 Inclined Manometer

Top inclined: scale 0.2

Middle inclined: scale 0.1

Bottom inclined: scale 0.05

Vertical: scale 1


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Fig.6.1 Inclined manometer setting

For example, if the manometer was top inclined and gave a reading of 25 mm of H2O, the

correct value would be 25 x 0.2 mm of H2O i.e. 5 mm of H2O.

8.9 Height Gauge: The height gauge used to vary the height of the instrument (Pitot tube or total pressure

tube) must be accurate. This height gauge used is accurate to a hundredth of a millimeter.

This kind of accuracy enables precise results, and it also enables the user to notice

fluctuations of pressure against minor changes in height.

Fig 6.2 Height gauge, accurate to one hundredth of a mm

Top inclined

Middle inclined

Bottom inclined


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Fig 6.3 Static pressure errors [19].

Chapter 9 Appendix II

9.1 Pitot Tube Limitations

The Pitot-tube can calculate the static pressure, dynamic pressure and total pressure at a

given point. However, there are some limitations.

The static pressure is usually difficult to measure accurately. The difference between true

(pstat) and measured (pstat.m) values of static pressure may be due to the following: [19]

1. Misalignment of the tube axis and velocity vector. The tube axis and velocity vector must

be parallel in order to achieve accurate results. Misalignment exposes the static taps to

some component of velocity.

2. Nonzero tube diameter. Streamlines next to the tube must be longer than those in

undisturbed flow, which indicates an increase in velocity.

3. Influence of stagnation point on the tube-support leading edge (dimensions of Pitot-static

tube). The higher pressure (at stagnation point) causes the static pressure upstream of the

leading edge also to be high causing inaccuracy. If the static taps are too close to the

support, they will read high because of this effect. However, this error and the error stated

above in item 2 tend to cancel. By proper design of the Pitot tube, the effect of this

cancellation may be achieved. Fig. 433 shows the nature of errors 2 and 3.

The errors in stagnation

pressure are likely to be smaller

than those in the static

pressure. Misalignment

prevents formation of a true

stagnation point at the

measuring hole since the

velocity is not zero.

The effect of viscosity can also

play a part in error

development. At sufficiently

low Reynolds number, the

viscosity of the fluid exerts a

noticeable additional force at

the stagnation hole, causing

the stagnation pressure to be

higher than predicted. The

following equation used

assumes the flow to be


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frictionless:

V = √[2(pstag – pstat)/ρ] [19]

Where V = flow velocity

ρ = fluid density (density of air = 1.2 kg/m3

pstag = stagnation or total pressure

pstat = static pressure

9.2 Total Pressure Tube.

A total pressure tube is a metal tube which reads the total pressure at a specific point when

connected to a manometer. Similar to a Pitot tube, the total pressure tube has a 90 degree

bend at the inlet. Unlike a Pitot tube, the total pressure tube has no major limitations to its

dimensions (see appendix).

To compensate the limitations of the Pitot tube because of its size, a total pressure tube can

be used. The Pitot tube was incapable of reading pressure at certain points around the car;

the pressure at these points was measured using a total pressure tube.

For example, the Pitot tube is incapable of measuring pressure at the very front end of the

car. It is suitable to use a total pressure tube (of smaller dimensions than the Pitot tube) to

measure pressure acting on this area of the car. The following figure illustrates the idea:

Fig 6.4 Case 1: measuring pressure at front of car using Pitot Tube

As seen in the Fig above, the Pitot tube is incapable of measuring pressure at point A. Point

B is the closest point to point A which the instrument is capable of reaching.

Pitot tube


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Although, a total pressure tube is capable of measuring pressure at point A because of its

smaller dimensions as illustrated case 2:

Fig 6.5 Case 2: measuring pressure at front of car using a total pressure tube.

The total pressure tube has its own limitations. The major limitation is that it can only read

the total pressure at a certain point, and not the dynamic head or static head.

9.2 Car Shapes

Fig. 6.6 Ford Fiesta (Hatchback) www.dekstopmachine.com

Total pressure

tube


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Fig. 6.7 Ford GT40 (Fastback) www.dekstopmachine.com

Fig. 6.8 Lincoln Town Car (Saloon) www.dekstopmachine.com

http://www.dekstopmachine.com/

http://www.dekstopmachine.com/

Northumbria University Final Year Project

2009-2010

Paramesh Nirmal 64

Chapter 10 Appendix III

Table 5: Experimental results for Hatchback. Wind Tunnel Setting: 8.5 m/s.

x coordinate

Point

height (y)

Dyamic head

reading

Dynamic Head

mm of H2O (x

0.1)


Static head reading

Static Head

mm of H2O (x

0.1)

Static, PSt

(N/m2)

Total head

reading

Total Head

mm of H2O (x

0.1)

Total Head,

PT (N/m2)

Velocity, v (ms-1)

330 1 0.00 -91.00 -9.10 -89.24 -40.00 -4.00 -39.23 -76.00 -7.60 -74.53 12.17

330 1 1.00 -90.00 -9.00 -88.26 -40.00 -4.00 -39.23 -76.00 -7.60 -74.53 12.11

330 1 2.00 -91.00 -9.10 -89.24 -40.00 -4.00 -39.23 -77.00 -7.70 -75.51 12.17

330 1 3.00 -92.00 -9.20 -90.22 -40.00 -4.00 -39.23 -77.00 -7.70 -75.51 12.24

330 1 4.00 -92.00 -9.20 -90.22 -40.00 -4.00 -39.23 -77.00 -7.70 -75.51 12.24

330 1 5.00 -94.00 -9.40 -92.18 -40.00 -4.00 -39.23 -77.00 -7.70 -75.51 12.37

330 1 6.00 -94.00 -9.40 -92.18 -40.00 -4.00 -39.23 -78.00 -7.80 -76.49 12.37

330 1 7.00 -96.00 -9.60 -94.14 -40.00 -4.00 -39.23 -79.00 -7.90 -77.47 12.50

330 1 8.00 -97.00 -9.70 -95.12 -40.00 -4.00 -39.23 -79.00 -7.90 -77.47 12.57

330 1 9.00 -98.00 -9.80 -96.11 -40.00 -4.00 -39.23 -79.00 -7.90 -77.47 12.63

330 1 10.00 -99.00 -9.90 -97.09 -40.00 -4.00 -39.23 -80.00 -8.00 -78.45 12.70

330 1 15.00 -100.00 -10.00 -98.07 -40.00 -4.00 -39.23 -80.00 -8.00 -78.45 12.76

330 1 20.00 -102.00 -10.20 -100.03 -40.00 -4.00 -39.23 -81.00 -8.10 -79.43 12.89

330 1 30.00 -104.00 -10.40 -101.99 -40.00 -4.00 -39.23 -83.00 -8.30 -81.40 13.02

330 1 40.00 -103.00 -10.30 -101.01 -40.00 -4.00 -39.23 -82.00 -8.20 -80.41 12.95


2009-2010

Paramesh Nirmal 65

330 1 60.00 -101.00 -10.10 -99.05 -40.00 -4.00 -39.23 -79.00 -7.90 -77.47 12.83

330 1 70.00 -96.00 -9.60 -94.14 -40.00 -4.00 -39.23 -76.00 -7.60 -74.53 12.50

330 1 80.00 -85.00 -8.50 -83.36 -40.00 -4.00 -39.23 -62.00 -6.20 -60.80 11.77

330 1 85.00 -51.00 -5.10 -50.01 -38.00 -3.80 -37.27 -42.00 -4.20 -41.19 9.11

330 1 90.00 -50.00 -5.00 -49.03 -37.00 -3.70 -36.28 -11.00 -1.10 -10.79 9.02

330 1 100.00 40.00 4.00 39.23 -36.00 -3.60 -35.30 -4.00 -0.40 -3.92 8.07

330 1 120.00 42.00 4.20 41.19 -34.00 -3.40 -33.34 -3.00 -0.30 -2.94 8.27

330 1 140.00 28.00 2.80 27.46 -34.00 -3.40 -33.34 -5.00 -0.50 -4.90 6.75

330 1 160.00 12.00 1.20 11.77 -31.00 -3.10 -30.40 -15.00 -1.50 -14.71 4.42

x coordinate

Point

height (y)

Dyamic head

reading

Dynamic Head

mm of H2O (x

0.1)


Static head reading

Static Head

mm of H2O (x

0.1)

Static, PSt

(N/m2)

Total head

reading

Total Head

mm of H2O (x

0.1)

Total Head,

PT (N/m2)

Velocity, v (ms-1)

290 2 70.00 45.00 4.50 44.13 -117.00 -11.70 -114.74 -119.00 -11.90 -116.70 8.56

290 2 75.00 46.00 4.60 45.11 -117.00 -11.70 -114.74 -119.00 -11.90 -116.70 8.66

290 2 80.00 48.00 4.80 47.07 -118.00 -11.80 -115.72 117.00 11.70 114.74 8.84

290 2 85.00 58.00 5.80 56.88 -116.00 -11.60 -113.76 -96.00 -9.60 -94.14 9.72

290 2 90.00 87.00 8.70 85.32 -114.00 -11.40 -111.80 -32.00 -3.20 -31.38 11.90

290 2 95.00 103.00 10.30 101.01 -114.00 -11.40 -111.80 -12.00 -1.20 -11.77 12.95

290 2 100.00 106.00 10.60 103.95 -110.00 -11.00 -107.87 -6.00 -0.60 -5.88 13.14

290 2 110.00 105.00 10.50 102.97 -107.00 -10.70 -104.93 -5.00 -0.50 -4.90 13.08

290 2 130.00 102.00 10.20 100.03 -103.00 -10.30 -101.01 -4.00 -0.40 -3.92 12.89


2009-2010

Paramesh Nirmal 66

290 2 150.00 97.00 9.70 95.12 -106.00 -10.60 -103.95 -17.00 -1.70 -16.67 12.57

x coordinate

Point

height (y)

Dyamic head

reading

Dynamic Head

mm of H2O (x

0.1)


Static head reading

Static Head

mm of H2O (x

0.1)

Static, PSt

(N/m2)

Total head

reading

Total Head

mm of H2O (x

0.1)

Total Head,

PT (N/m2)

Velocity, v (ms-1)

200 3.5 120.00 142.00 14.20 139.25 -146.00 -14.60 -143.18 -7.00 -0.70 -6.86 15.21

200 3.5 125.00 140.00 14.00 137.29 -145.00 -14.50 -142.20 -2.00 -0.20 -1.96 15.10

200 3.5 130.00 139.00 13.90 136.31 -139.00 -13.90 -136.31 -2.00 -0.20 -1.96 15.05

200 3.5 135.00 136.00 13.60 133.37 -135.00 -13.50 -132.39 -2.00 -0.20 -1.96 14.88

200 3.5 140.00 133.00 13.30 130.43 -132.00 -13.20 -129.45 -2.00 -0.20 -1.96 14.72

200 3.5 145.00 130.00 13.00 127.49 -128.00 -12.80 -125.53 -2.00 -0.20 -1.96 14.55

200 3.5 150.00 127.00 12.70 124.54 -126.00 -12.60 -123.56 -2.00 -0.20 -1.96 14.38

200 3.5 155.00 124.00 12.40 121.60 -124.00 -12.40 -121.60 -4.00 -0.40 -3.92 14.21

200 3.5 160.00 120.00 12.00 117.68 -121.00 -12.10 -118.66 -11.00 -1.10 -10.79 13.98

x coordinate

Point

height (y)

Dyamic head

reading

Dynamic Head

mm of H2O (x

0.1)


Static head reading

Static Head

mm of H2O (x

0.1)

Static, PSt

(N/m2)

Total head

reading

Total Head

mm of H2O (x

0.1)

Total Head,

PT (N/m2)

Velocity, v (ms-1)


2009-2010

Paramesh Nirmal 67

5 6.5 40.00 76.00 7.60 74.53 -81.00 -8.10 -79.43 -6.00 -0.60 -5.88 11.13

5 6.5 45.00 73.00 7.30 71.59 -78.00 -7.80 -76.49 -6.00 -0.60 -5.88 10.90

5 6.5 50.00 70.00 7.00 68.65 -74.00 -7.40 -72.57 -6.00 -0.60 -5.88 10.68

5 6.5 55.00 70.00 7.00 68.65 -74.00 -7.40 -72.57 -4.00 -0.40 -3.92 10.68

5 6.5 60.00 70.00 7.00 68.65 -75.00 -7.50 -73.55 -3.00 -0.30 -2.94 10.68

5 6.5 80.00 70.00 7.00 68.65 -73.00 -7.30 -71.59 -2.00 -0.20 -1.96 10.68

5 6.5 100.00 70.00 7.00 68.65 -74.00 -7.40 -72.57 -2.00 -0.20 -1.96 10.68

5 6.5 120.00 70.00 7.00 68.65 -73.00 -7.30 -71.59 -3.00 -0.30 -2.94 10.68

5 6.5 140.00 59.00 5.90 57.86 -74.00 -7.40 -72.57 -15.00 -1.50 -14.71 9.80

24/02/2010

Pitot Tube placed facing the rear

x coordinate

Point

height (y)

Dyamic head

reading

Dynamic Head

mm of H2O (x 0.05)

(bottom inclined


Velocity, v (ms-1)

Static head

reading

Static Head

mm of H2O (x

0.1)

Static, PSt

(N/m2)

Total head

reading

Total Head

mm of H2O (x

0.1)

Velocity, v (ms-1)

370 0 0.00 35.00 1.75 17.16 5.34 -140.00 -14.00 -137.29 -120.00 -12.00 5.34

370 0 1.00 35.00 1.75 17.16 5.34 -140.00 -14.00 -137.29 -122.00 -12.20 5.34

370 0 2.00 34.00 1.70 16.67 5.26 -140.00 -14.00 -137.29 -122.00 -12.20 5.26

370 0 3.00 32.00 1.60 15.69 5.11 -140.00 -14.00 -137.29 -122.00 -12.20 5.11

370 0 4.00 31.00 1.55 15.20 5.02 -140.00 -14.00 -137.29 -123.00 -12.30 5.02

370 0 5.00 29.00 1.45 14.22 4.86 -140.00 -14.00 -137.29 -125.00 -12.50 4.86

370 0 6.00 27.00 1.35 13.24 4.69 -140.00 -14.00 -137.29 -127.00 -12.70 4.69

370 0 7.00 27.00 1.35 13.24 4.69 -140.00 -14.00 -137.29 -128.00 -12.80 4.69


2009-2010

Paramesh Nirmal 68

370 0 8.00 25.00 1.25 12.26 4.51 -140.00 -14.00 -137.29 -130.00 -13.00 4.51

370 0 9.00 24.00 1.20 11.77 4.42 -140.00 -14.00 -137.29 -130.00 -13.00 4.42

370 0 10.00 21.00 1.05 10.30 4.14 -140.00 -14.00 -137.29 -130.00 -13.00 4.14

370 0 15.00 20.00 1.00 9.81 4.04 -140.00 -14.00 -137.29 -134.00 -13.40 4.04

370 0 20.00 16.00 0.80 7.85 3.61 -140.00 -14.00 -137.29 -135.00 -13.50 3.61

370 0 30.00 12.00 0.60 5.88 3.13 -142.00 -14.20 -139.25 -136.00 -13.60 3.13

370 0 40.00 10.00 0.50 4.90 2.85 -142.00 -14.20 -139.25 -138.00 -13.80 2.85

370 0 60.00 6.00 0.30 2.94 2.21 -142.00 -14.20 -139.25 -135.00 -13.50 2.21

370 0 70.00 9.00 0.45 4.41 2.71 -142.00 -14.20 -139.25 -130.00 -13.00 2.71

370 0 80.00 10.00 0.50 4.90 2.85 -135.00 -13.50 -132.39 -125.00 -12.50 2.85

370 0 85.00 10.00 0.50 4.90 2.85 -131.00 -13.10 -128.47 -125.00 -12.50 2.85

370 0 90.00 8.00 0.40 3.92 2.55 -130.00 -13.00 -127.49 -121.00 -12.10 2.55

370 0 100.00 7.00 0.35 3.43 2.39 -125.00 -12.50 -122.58 -117.00 -11.70 2.39

370 0 120.00 7.00 0.35 3.43 2.39 -121.00 -12.10 -118.66 -117.00 -11.70 2.39

370 0 140.00 9.00 0.45 4.41 2.71 -120.00 -12.00 -117.68 -117.00 -11.70 2.71

370 0 160.00 17.00 0.85 8.34 3.72 -130.00 -13.00 -127.49 -114.00 -11.40 3.72

Pitot facing towards the front

x coordinate

Point

height (y)

Dyamic head

reading

Dynamic Head

mm of H2O (x

0.1)


Velocity, v (ms-1)

Static head

reading

Static Head

mm of H2O (x

0.1)

Static, PSt

(N/m2)

Total head

reading

Total Head

mm of H2O (x

0.1)

Velocity, v (ms-1)

370 0 0.00 -23.00 -2.30 -22.56 6.12 -139.00 -13.90 -136.31 -85.00 -8.50 6.12


2009-2010

Paramesh Nirmal 69

370 0 1.00 -23.00 -2.30 -22.56 6.12 -137.00 -13.70 -134.35 -86.00 -8.60 6.12

370 0 2.00 -24.00 -2.40 -23.54 6.25 -139.00 -13.90 -136.31 -85.00 -8.50 6.25

370 0 3.00 -24.00 -2.40 -23.54 6.25 -138.00 -13.80 -135.33 -85.00 -8.50 6.25

370 0 4.00 -24.00 -2.40 -23.54 6.25 -139.00 -13.90 -136.31 -87.00 -8.70 6.25

370 0 5.00 -23.00 -2.30 -22.56 6.12 -139.00 -13.90 -136.31 -88.00 -8.80 6.12

370 0 6.00 -23.00 -2.30 -22.56 6.12 -139.00 -13.90 -136.31 -90.00 -9.00 6.12

370 0 7.00 -23.00 -2.30 -22.56 6.12 -139.00 -13.90 -136.31 -88.00 -8.80 6.12

370 0 8.00 -23.00 -2.30 -22.56 6.12 -139.00 -13.90 -136.31 -88.00 -8.80 6.12

370 0 9.00 -23.00 -2.30 -22.56 6.12 -139.00 -13.90 -136.31 -90.00 -9.00 6.12

370 0 10.00 -22.00 -2.20 -21.57 5.99 -139.00 -13.90 -136.31 -91.00 -9.10 5.99

370 0 15.00 -19.00 -1.90 -18.63 5.56 -139.00 -13.90 -136.31 -93.00 -9.30 5.56

370 0 20.00 -19.00 -1.90 -18.63 5.56 -139.00 -13.90 -136.31 -95.00 -9.50 5.56

370 0 30.00 -20.00 -2.00 -19.61 5.71 -139.00 -13.90 -136.31 -96.00 -9.60 5.71

370 0 40.00 -20.00 -2.00 -19.61 5.71 -140.00 -14.00 -137.29 -96.00 -9.60 5.71

370 0 60.00 -19.00 -1.90 -18.63 5.56 -140.00 -14.00 -137.29 -71.00 -7.10 5.56

370 0 70.00 74.00 7.40 72.57 10.98 -140.00 -14.00 -137.29 -40.00 -4.00 10.98

370 0 80.00 79.00 7.90 77.47 11.34 -139.00 -13.90 -136.31 -20.00 -2.00 11.34

370 0 85.00 87.00 8.70 85.32 11.90 -136.00 -13.60 -133.37 -16.00 -1.60 11.90

370 0 90.00 90.00 9.00 88.26 12.11 -130.00 -13.00 -127.49 -14.00 -1.40 12.11

370 0 100.00 94.00 9.40 92.18 12.37 -127.00 -12.70 -124.54 -10.00 -1.00 12.37

370 0 120.00 84.00 8.40 82.38 11.70 -120.00 -12.00 -117.68 -5.00 -0.50 11.70

370 0 140.00 48.00 4.80 47.07 8.84 -121.00 -12.10 -118.66 -10.00 -1.00 8.84

370 0 160.00 37.00 3.70 36.28 7.76 -130.00 -13.00 -127.49 -19.00 -1.90 7.76


2009-2010

Paramesh Nirmal 70

Pitot facing the front

x coordinate

Point

height (y)

Dyamic head

reading

Dynamic Head

mm of H2O (x

0.1)


Velocity, v (ms-1)

Static head

reading

Static Head

mm of H2O (x

0.1)

Static, PSt

(N/m2)

Total head

reading

Total Head

mm of H2O (x

0.1)

Velocity, v (ms-1)

370 0 0.00 -16.00 -1.60 -15.69 5.11 -116.00 -11.60 -113.76 -130.00 -13.00 5.11

370 0 5.00 -16.00 -1.60 -15.69 5.11 -114.00 -11.40 -111.80 -130.00 -13.00 5.11

370 0 10.00 -16.00 -1.60 -15.69 5.11 -117.00 -11.70 -114.74 -131.00 -13.10 5.11

370 0 15.00 -15.00 -1.50 -14.71 4.94 -120.00 -12.00 -117.68 -132.00 -13.20 4.94

370 0 20.00 -15.00 -1.50 -14.71 4.94 -122.00 -12.20 -119.64 -134.00 -13.40 4.94

370 0 30.00 -14.00 -1.40 -13.73 4.78 -118.00 -11.80 -115.72 -134.00 -13.40 4.78

370 0 40.00 -10.00 -1.00 -9.81 4.04 -122.00 -12.20 -119.64 -134.00 -13.40 4.04

370 0 50.00 -5.00 -0.50 -4.90 2.85 -126.00 -12.60 -123.56 -127.00 -12.70 2.85

370 0 60.00 23.00 2.30 22.56 6.12 -125.00 -12.50 -122.58 -90.00 -9.00 6.12

370 0 70.00 69.00 6.90 67.67 10.60 -124.00 -12.40 -121.60 -57.00 -5.70 10.60

370 0 80.00 85.00 8.50 83.36 11.77 -120.00 -12.00 -117.68 -24.00 -2.40 11.77

370 0 90.00 88.00 8.80 86.30 11.97 -116.00 -11.60 -113.76 -15.00 -1.50 11.97

370 0 100.00 95.00 9.50 93.16 12.44 -111.00 -11.10 -108.85 -10.00 -1.00 12.44

370 0 120.00 98.00 9.80 96.11 12.63 -80.00 -8.00 -78.45 -5.00 -0.50 12.63

370 0 140.00 95.00 9.50 93.16 12.44 -79.00 -7.90 -77.47 -13.00 -1.30 12.44

370 0 160.00 79.00 7.90 77.47 11.34 -75.00 -7.50 -73.55 -27.00 -2.70 11.34


2009-2010

Paramesh Nirmal 71

Pitot facing the rear

x coordinate

Point

height (y)

Dyamic head

reading

Dynamic Head

mm of H2O (x

0.1)


Velocity, v (ms-1) Static

head reading

Static Head

mm of H2O (x

0.1)

Static, PSt

(N/m2)

Total head

reading

Total Head

mm of H2O (x

0.1)

Velocity, v (ms-1)

370 0 0.00 17.00 1.70 16.67 5.26 -116.00 -11.60 -113.76 -116.00 -11.60

370 0 5.00 10.00 1.00 9.81 4.04 -114.00 -11.40 -111.80 -121.00 -12.10

370 0 10.00 6.00 0.60 5.88 3.13 -117.00 -11.70 -114.74 -127.00 -12.70

370 0 15.00 5.00 0.50 4.90 2.85 -122.00 -12.20 -119.64 -130.00 -13.00

370 0 20.00 4.00 0.40 3.92 2.55 -122.00 -12.20 -119.64 -131.00 -13.10

370 0 30.00 3.00 0.30 2.94 2.21 -120.00 -12.00 -117.68 -134.00 -13.40

370 0 40.00 3.00 0.30 2.94 2.21 -122.00 -12.20 -119.64 -134.00 -13.40

370 0 50.00 3.00 0.30 2.94 2.21 -126.00 -12.60 -123.56 -134.00 -13.40

370 0 60.00 4.00 0.40 3.92 2.55 -125.00 -12.50 -122.58 -135.00 -13.50

370 0 70.00 4.00 0.40 3.92 2.55 -125.00 -12.50 -122.58 -131.00 -13.10

370 0 80.00 4.00 0.40 3.92 2.55 -120.00 -12.00 -117.68 -125.00 -12.50

370 0 90.00 1.00 0.10 0.98 1.28 -116.00 -11.60 -113.76 -122.00 -12.20

370 0 100.00 2.00 0.20 1.96 1.80 -112.00 -11.20 -109.83 -119.00 -11.90

370 0 120.00 5.00 0.50 4.90 2.85 -81.00 -8.10 -79.43 -115.00 -11.50

370 0 140.00 7.00 0.70 6.86 3.38 -77.00 -7.70 -75.51 -116.00 -11.60

370 0 160.00 10.00 1.00 9.81 4.04 -71.00 -7.10 -69.63 -117.00 -11.70


2009-2010

Paramesh Nirmal 72

Reynolds number = ρvl/μ ρ = density of air = 1.2 kg/m3

Re= 183943.8

v = 8.5 m/s Generally,

l = length of car = 321 mm

If Re >2000, flow is turbulent μ = viscosity of air = 1.78 x 10-5 kg/ms

If Re<2000, flow is laminar


2009-2010

Paramesh Nirmal 73

Table 6: Experimental Results for Fastback. Wind tunnel setting: 8.5m/s.

x-coordinate

Height above

platform (y/mm)

Dyamic head

reading

Dynamic Head

mm of H2O (x

0.1)


Static head

reading

Static Head

mm of H2O (x

0.1)

Static, PSt

(N/m2)

Total head

reading

Total Head

mm of H2O (x

0.1)

Total Head,

PT (N/m2)

Theoretical Total

Head, PTh (N/m2)

Velocity, v (ms-1)

1 0.00 51.00 5.10 50.01 -109.00 -10.90 -106.89 -107.00 -10.70 -104.93 -56.88 9.11

2 25.00 45.00 4.50 44.13 -110.00 -11.00 -107.87 -110.00 -11.00 -107.87 -63.74 8.56

2 27.00 44.00 4.40 43.15 -110.00 -11.00 -107.87 -110.00 -11.00 -107.87 -64.72 8.47

2 29.00 43.00 4.30 42.17 -110.00 -11.00 -107.87 -110.00 -11.00 -107.87 -65.70 8.37

2 31.00 43.00 4.30 42.17 -110.00 -11.00 -107.87 -110.00 -11.00 -107.87 -65.70 8.37

2 33.00 43.00 4.30 42.17 -110.00 -11.00 -107.87 -110.00 -11.00 -107.87 -65.70 8.37

2 35.00 43.00 4.30 42.17 -110.00 -11.00 -107.87 -110.00 -11.00 -107.87 -65.70 8.37

2 40.00 43.00 4.30 42.17 -109.00 -10.90 -106.89 -110.00 -11.00 -107.87 -64.72 8.37

2 45.00 43.00 4.30 42.17 -108.00 -10.80 -105.91 -110.00 -11.00 -107.87 -63.74 8.37

2 55.00 43.00 4.30 42.17 -107.00 -10.70 -104.93 -110.00 -11.00 -107.87 -62.76 8.37

2 65.00 62.00 6.20 60.80 -105.00 -10.50 -102.97 -100.00 -10.00 -98.07 -42.17 10.05

2 70.00 70.00 7.00 68.65 -104.00 -10.40 -101.99 -57.00 -5.70 -55.90 -33.34 10.68

2 75.00 84.00 8.40 82.38 -102.00 -10.20 -100.03 -39.00 -3.90 -38.25 -17.65 11.70

2 80.00 91.00 9.10 89.24 -100.00 -10.00 -98.07 -15.00 -1.50 -14.71 -8.83 12.17

2 85.00 95.00 9.50 93.16 -98.00 -9.80 -96.11 -10.00 -1.00 -9.81 -2.94 12.44

2 95.00 95.00 9.50 93.16 -94.00 -9.40 -92.18 -2.00 -0.20 -1.96 0.98 12.44

2 115.00 93.00 9.30 91.20 -93.00 -9.30 -91.20 -2.00 -0.20 -1.96 0.00 12.31

2 135.00 93.00 9.30 91.20 -91.00 -9.10 -89.24 -2.00 -0.20 -1.96 1.96 12.31

3 55.00 -51.00 -5.10 -50.01 -38.00 -3.80 -37.27 -42.00 -4.20 -41.19 -87.28 9.11

3 57.00 -5.00 -0.50 -4.90 -37.00 -3.70 -36.28 -11.00 -1.10 -10.79 -41.19 2.85


2009-2010

Paramesh Nirmal 74

3 59.00 40.00 4.00 39.23 -36.00 -3.60 -35.30 -4.00 -0.40 -3.92 3.92 8.07

3 61.00 42.00 4.20 41.19 -34.00 -3.40 -33.34 -3.00 -0.30 -2.94 7.85 8.27

3 63.00 28.00 2.80 27.46 -34.00 -3.40 -33.34 -5.00 -0.50 -4.90 -5.88 6.75

3 65.00 12.00 1.20 11.77 -31.00 -3.10 -30.40 -15.00 -1.50 -14.71 -18.63 4.42

4 60.00 -36.00 -3.60 -35.30 -40.00 -4.00 -39.23 -65.00 -6.50 -63.74 -74.53 7.66

4 62.00 -25.00 -2.50 -24.52 -40.00 -4.00 -39.23 -58.00 -5.80 -56.88 -63.74 6.38

4 64.00 -6.00 -0.60 -5.88 -40.00 -4.00 -39.23 -50.00 -5.00 -49.03 -45.11 3.13

4 66.00 29.00 2.90 28.44 -40.00 -4.00 -39.23 -27.00 -2.70 -26.48 -10.79 6.87

4 68.00 32.00 3.20 31.38 -40.00 -4.00 -39.23 -8.00 -0.80 -7.85 -7.85 7.22

4 70.00 35.00 3.50 34.32 -40.00 -4.00 -39.23 -6.00 -0.60 -5.88 -4.90 7.55

4 75.00 39.00 3.90 38.25 -40.00 -4.00 -39.23 -2.00 -0.20 -1.96 -0.98 7.97

4 80.00 40.00 4.00 39.23 -40.00 -4.00 -39.23 -2.00 -0.20 -1.96 0.00 8.07

4 90.00 40.00 4.00 39.23 -41.00 -4.10 -40.21 -2.00 -0.20 -1.96 -0.98 8.07

4 110.00 40.00 4.00 39.23 -40.00 -4.00 -39.23 -2.00 -0.20 -1.96 0.00 8.07

4 130.00 40.00 4.00 39.23 -40.00 -4.00 -39.23 -2.00 -0.20 -1.96 0.00 8.07

5 67.00 151.00 15.10 148.08 -157.00 -15.70 -153.96 -31.00 -3.10 -30.40 -5.88 15.68

5 69.00 137.00 13.70 134.35 -138.00 -13.80 -135.33 -10.00 -1.00 -9.81 -0.98 14.94

5 71.00 135.00 13.50 132.39 -136.00 -13.60 -133.37 -6.00 -0.60 -5.88 -0.98 14.83

5 73.00 134.00 13.40 131.41 -135.00 -13.50 -132.39 -5.00 -0.50 -4.90 -0.98 14.77

5 75.00 133.00 13.30 130.43 -134.00 -13.40 -131.41 -4.00 -0.40 -3.92 -0.98 14.72

5 77.00 132.00 13.20 129.45 -132.00 -13.20 -129.45 -4.00 -0.40 -3.92 0.00 14.66

5 82.00 130.00 13.00 127.49 -128.00 -12.80 -125.53 -3.00 -0.30 -2.94 1.96 14.55

5 87.00 127.00 12.70 124.54 -123.00 -12.30 -120.62 -3.00 -0.30 -2.94 3.92 14.38

5 97.00 121.00 12.10 118.66 -116.00 -11.60 -113.76 -3.00 -0.30 -2.94 4.90 14.04

5 117.00 115.00 11.50 112.78 -109.00 -10.90 -106.89 -3.00 -0.30 -2.94 5.88 13.69

5 137.00 107.00 10.70 104.93 -108.00 -10.80 -105.91 -3.00 -0.30 -2.94 -0.98 13.20


2009-2010

Paramesh Nirmal 75

7 40.00 86.00 8.60 84.34 -87.00 -8.70 -85.32 -8.00 -0.80 -7.85 -0.98 11.84

7 42.00 83.00 8.30 81.40 -87.00 -8.70 -85.32 -6.00 -0.60 -5.88 -3.92 11.63

7 44.00 82.00 8.20 80.41 -86.00 -8.60 -84.34 -5.00 -0.50 -4.90 -3.92 11.56

7 46.00 82.00 8.20 80.41 -85.00 -8.50 -83.36 -4.00 -0.40 -3.92 -2.94 11.56

7 48.00 82.00 8.20 80.41 -85.00 -8.50 -83.36 -2.00 -0.20 -1.96 -2.94 11.56

7 50.00 82.00 8.20 80.41 -84.00 -8.40 -82.38 -2.00 -0.20 -1.96 -1.96 11.56

7 55.00 81.00 8.10 79.43 -84.00 -8.40 -82.38 -3.00 -0.30 -2.94 -2.94 11.49

7 60.00 82.00 8.20 80.41 -84.00 -8.40 -82.38 -2.00 -0.20 -1.96 -1.96 11.56

7 70.00 83.00 8.30 81.40 -84.00 -8.40 -82.38 -2.00 -0.20 -1.96 -0.98 11.63

7 90.00 84.00 8.40 82.38 -85.00 -8.50 -83.36 -2.00 -0.20 -1.96 -0.98 11.70

7 110.00 85.00 8.50 83.36 -86.00 -8.60 -84.34 -2.00 -0.20 -1.96 -0.98 11.77

7.5 30.00 96.00 9.60 94.14 -97.00 -9.70 -95.12 -6.00 -0.60 -5.88 -0.98 12.50

7.5 32.00 95.00 9.50 93.16 -96.00 -9.60 -94.14 -5.00 -0.50 -4.90 -0.98 12.44

7.5 34.00 95.00 9.50 93.16 -95.00 -9.50 -93.16 -4.00 -0.40 -3.92 0.00 12.44

7.5 36.00 94.00 9.40 92.18 -92.00 -9.20 -90.22 -4.00 -0.40 -3.92 1.96 12.37

7.5 38.00 93.00 9.30 91.20 -93.00 -9.30 -91.20 -3.00 -0.30 -2.94 0.00 12.31

7.5 40.00 90.00 9.00 88.26 -91.00 -9.10 -89.24 -3.00 -0.30 -2.94 -0.98 12.11

7.5 45.00 86.00 8.60 84.34 -88.00 -8.80 -86.30 -3.00 -0.30 -2.94 -1.96 11.84

7.5 50.00 82.00 8.20 80.41 -86.00 -8.60 -84.34 -3.00 -0.30 -2.94 -3.92 11.56

7.5 60.00 78.00 7.80 76.49 -82.00 -8.20 -80.41 -2.00 -0.20 -1.96 -3.92 11.27

7.5 80.00 74.00 7.40 72.57 -80.00 -8.00 -78.45 -2.00 -0.20 -1.96 -5.88 10.98

7.5 100.00 76.00 7.60 74.53 -77.00 -7.70 -75.51 -3.00 -0.30 -2.94 -0.98 11.13


2009-2010

Paramesh Nirmal 76

Table 7: Preliminary Readings

Pitot Static Tube

Copper Total Head Tube

Height above

datumn (h/mm)

Dynamic head

reading

Dynamic Head

mm of H2O (x

0.1)

Dynamic Head, Pd (N/m2)

Static Head

Reading

Static Head

mm of H2O (x

0.1)

Static Head,

Ps (N/m2)

Theoretical Total Head (Pth) N/m2

Total Head

Reading

Total Head

mm of H2O (x

0.1)

Total Head,

PT (N/m2)

Total head

reading from Total head tube

Total Head

mm of H2O (x

0.1)

Total Head,

PT (N/m2)

0.0 74 7.4 72.57 -75 -7.5 -73.55 -0.98 -2 -0.2 -1.96 -8 -0.8 -7.85

20.0 75 7.5 73.55 -75 -7.5 -73.55 0.00 -2 -0.2 -1.96 -2 -0.2 -1.96

40.0 75 7.5 73.55 -75 -7.5 -73.55 0.00 -2 -0.2 -1.96 -3 -0.3 -2.94

60.0 74 7.4 72.57 -74 -7.4 -72.57 0.00 -2 -0.2 -1.96 -3 -0.3 -2.94

80.0 72 7.2 70.61 -73 -7.3 -71.59 -0.98 -2 -0.2 -1.96 -2 -0.2 -1.96

100.0 72 7.2 70.61 -72 -7.2 -70.61 0.00 -3 -0.3 -2.94 -2 -0.2 -1.96

120.0 72 7.2 70.61 -72 -7.2 -70.61 0.00 -3 -0.3 -2.94 -2 -0.2 -1.96

140.0 71 7.1 69.63 -70 -7 -68.65 0.98 -4 -0.4 -3.92 -6 -0.6 -5.88

160.0 66 6.6 64.72 -70 -7 -68.65 -3.92 -10 -1 -9.81 -11 -1.1 -10.79


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10.1 Project Costing There are various costs involved in an experimental project. The costs include cost of labour,

equipment, software, etc.

The following table shows the estimated costs involved in the project and an estimated total

cost:

Field Cost/hr (£) Hours Cost (£)

Employee 20 400 8000

Supervisor 45 26 1170

Technician 30 4 120

Wind Tunnel cost 10 20 200

Cost of car shapes - - 80

Cost of materials - - 50

Cost of CFD Software & License - - 2500

Total Cost £ 12,120

Table 8. Estimated project costing.

The Gant Chart overleaf shows the project planning.


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28-S

ep

05-O

ct

12-O

ct

19-O

ct

26-O

ct

02-N

ov

09-N

ov

16-N

ov

23-N

ov

30-N

ov

07-D

ec

14-D

ec

21-D

ec

28-D

ec

04-J

an

11-J

an

18-J

an

25-J

an

01-F

eb

08-F

eb

15-F

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22-F

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01-M

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08-M

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15-M

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22-M

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29-M

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05-A

pr

Project Proposal

Research

Complete background

Complete literature review

Complete draft document

Practice CFD software (FLUENT)

Build different car shapes on FLUENT

Design Apparatus

Build Apparatus

Acquire car shells

Wind tunnel preliminary testing

Wind tunnel testing of 3 different shapes

CFD testing

Analyse results

Compare results

Discussion of results

Conclude

Hand in final document to Reaz

Final improvements

Gantt Chart


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School of Computing, Engineering and Information Sciences

Project Specification Form

Project Details

Course: Mechanical Engineering Full Time

Student's Name: Paramesh Nirmal

Project Title: Flow measurement of different car shapes

Project Supervisor: Reaz Hasan

Project Location: Northumbria University

Background to the Project:

The shapes of cars have changed in the past few decades to enhance them

aerodynamically. New cars are streamlined to reduce fuel emissions and improve

performance by increasing their aerodynamic characteristics. Car shapes are tested,

experimentally and mathematically; ideally, using a wind tunnel and computational

fluid dynamics (CFD) software.

Overall Aims of the Project:

To establish an experimental technique to install the models in the wind tunnel and

obtain experimental data. To test the aerodynamics of different car shapes using the

wind tunnel and CFD software. To understand what makes the flow features different

around different car shapes.

Envisaged End Point of the Project:

- Design and build an experimental facility to measure pressure, drag force, flow

velocity etc in the wind tunnel.

- Test and establish the accuracy of this facility.

- Fully test at least 3 different car shapes in both the wind tunnel and using CFD.

- Both results are analysed and compared.

- Understand the differences between the two methods and their accuracy.

Approved by supervisor:................................... Date: ...................................


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School of Computing, Engineering and Information Sciences

Project Risk Assessment

Name: Paramesh Nirmal

Course: Mechanical Engineering Full Time

Project Title: Flow measurement of different car shapes

Supervisor: Reaz Hasan Project Location: Northumbria

University

List the significant hazards associated with your project.

The instruments used in the project are not significantly dangerous. The only hazard

that can be considered is the rotating blades of the wind tunnel. However, the rotating

blades are protected by a cage to ensure safety.

List the other people at risk:

Other people/colleagues working in the lab may be at risk if they accidently get

caught with the rotating blades of the wind tunnel.

Risk Control

Are you aware that no one is allowed to work alone in the laboratory? YES

Describe the working procedures to be used to minimise risk:

I should ensure that I keep my hands away from the rotating blades of the wind tunnel

to prevent any accidents. Any small parts/tools should be kept at a distance from the

rotating blades to prevent accidents. It would be necessary to take precautions

ensuring that nobody but myself gets too close to the equipment.

When will you and your supervisor review the risk assessment?

When the experimentation has started

Signature: Paramesh Nirmal (Student) .................................. (Supervisor)

Date:……………………

Final Document Dissertation Paramesh Nirmal

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