(Introduction to Aerospace)EAS105 -Lab1

8/7/2019 (Introduction to Aerospace)EAS105 -Lab1

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Mohd Ashraf Mohd Ismail

Laboratory Experiment 1

Name : Mohammed Ashraf Bin Mohammed Ismail

Student No: N0806406

Contact No: 98225529

Date Submitted:

Lab. : Flow Visualization

Course Instructor: Mr Roger Chua



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Table of Contents

Abstract..........................................................................................................................3

INTRODUCTION.........................................................................................................4

DEFINATION ............................................................................................................... 5

EXPIREMENT RESULT.............................................................................................. 6Cylinder diameter(12mm) ......................................................................................... 6

Slow Speed at 0 Degree Angle of Bank ................................................................6Fast Speed at 0 Degree Angle of Bank ..................................................................6

Cylinder diameter(25mm) ......................................................................................... 6Slow Speed at 0 Degree Angle of Bank ................................................................6Fast Speed at 0 Degree Angle of Bank ..................................................................6

2mm thick plate curved plate.....................................................................................7Slow Speed at 0 Degree Angle of Bank ................................................................7Fast Speed at 0 Degree Angle of Bank ..................................................................7

Block of Dimension 70mmX25mmX40mm .............................................................7Slow Speed at 0 Degree Angle of Bank ................................................................7Fast Speed at 0 Degree Angle of Bank ..................................................................7

2mm thick plate rounded on one side ........................................................................ 8Slow Speed at 0 Degree Angle of Bank ................................................................8Slow Speed at 15 Degree Angle of Bank ..............................................................8Fast Speed at 0 Degree Angle of Bank ..................................................................8Fast Speed at 15 Degree Angle of Bank ................................................................8

Symmetrical Aerodynamic Wing Model................................................................... 9Slow Speed at 0 Degree Angle of Bank ................................................................9Slow Speed at15 Degree Angle of Bank ...............................................................9Fast Speed at 0 Degree Angle of Bank ..................................................................9Fast Speed at 15Degree Angle of Bank.................................................................9

DISCUSSION OF RESULT........................................................................................ 10

CONCLUSION............................................................................................................ 11

APPENDIX and REFERENCE................................................................................... 12



Introduction to Aerospace Engineering Lab 1 3

Abstract

This lab work is concerned with the experimental studies of the aerodynamic airflow

over different types of objects. Object used are of different size and dimension and in

some instances the angle of attack is being adjusted. Flow Visualisation technique is

used to clarify the flow behavior, of air especially wake structure behind the objects.

In this experiment we shall show how the behavior of the boundary layer can affect

lift, drag, and separation. We will use 8 different types of geometrical shape in our

experiment and in various stage changing the air speed and the angle of attack



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IntroductionIn the study of aerodynamic, understanding of the influence of the ‘boundary layer’

over the aerofoil is very important. The boundary layer is a very thin layer of air that

is closed to the aerofoil and “understanding it holds the key on how air flow behave,

and particular how lift is generated” [1]

Boundary layer is the friction of air molecules with the surface of the airfoil that

caused this change in speed. It’s the air closest to the airfoil till the edge of the layer

as the position where the flow speed reaches 99% of the free stream value.

Figure 1

The boundary layer will grow thicker as it gets further away from the leading edge.

There are 2 forms of boundary flow a)Laminar flow b)Turbulent flow

The Boundary layer can be separated into 5 main parts. 1)Laminar Flow,

2)Turbulent Flow ,3)Separation Point 4) Transition Point 5)Stagnation Point




Definition

Laminar Flow - Is the smooth, uninterrupted flow of air over the contour of the

wings, fuselage, or other parts of an aircraft in flight.

Turbulent Flow - Turbulent flow is when the air is subject to continual changes in

speed and direction. It consists of irregular eddies (circular currents) of air that push

on a surface in unexpected ways.

Transition Point – An instability develops and is the point when laminar flowchanges to turbulent flow

Separation Point – Is the point when the air can no longer return to the original free

stream condition It is because of this action therefore the boundary layer at this point

gets thicker and creates the formation of “wakes”. Beyond this point air will flow in

the reverse direction and a stall will occure.

Stagnation Point – Is the flow of the air that gets slowed down by following the

dividing streamline as it approaches the aerofoil.(First point of contact)

Angle of Attack (AoA) - The Angle at which the wing Strikes the air stream.

Figure 2



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Experimental Procedure and Result

Slow 12mm

Fast 12mm




Slow

Fast

Slow

Fast



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Slow Speed 0(AOA)

Fast Speed 0(AOA)

Slow Speed 15AOA)

Fast Speed 15 (AOA)




Slow Symmetrical 0(AOA)

Fast Symmetrical 0(AOA)

Slow Symmetrical 15(AoA)

Fast Symmetrical 15(AOA)



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Discussion of Result

Cylinder diameter (12mm) & (25mm)

• The faster the airspeed, the more turbulent the air flow becomes (Both)

• For the 25mm, the airflow is more turbulent but it tends to follow the contour of the shape after passing through rather that than the 12mm which formssmall eddies after pass through right behind the shape.

• More resistances for the 25mm at the stagnation point than the 12mm

2mm thick plate curved plate

• The air follows the contour of the shape better on the upper side

• The air flow is more laminar at slow speed that at fast speed

• At faster airspeed, the air flow still follows the contour of the shape on theupper side but becomes drastically turbulent at the lower side. Eddies to startform on the lower side and furthermore lower flowing air is also met withgreat resistance because of the curved shape on the lower part

Block of Dimension 70mmX25mmX40mm

• Not much difference between the both a fast speed and slow speed.

• The resistance, (Stagnation point) seems to be more at faster speed.

2mm thick plate rounded on one side

• At 0 (AOA) for slow and fast speed, the airflow is very ideal; it is laminar flow and follows the contour of the shape.

• At 15 (AOA) for slow speed, the airflow is still very ideal, only at fast speed;the separation point is nearly at the tip of the object. Airflow on top is veryturbulent and air flow below is met with some resistance as it comes in contactwith the structure.

Symmetrical Aerodynamic Wing Model

• At 0 (AOA) for the slow and fast speed the airflow is ideal. At Slow speed, theair tends to follow the shape of the contour very closely but at fast speed it stillfollow the contour only slightly further away

• At 15 (AOA) for slow speed the airflow is still ideal, only at fast speed, theairflow starts to separates (separation point) and nearly ¾ of the aerofoil .Airflow on top looks slightly more bumpy that at slow speed.




Conclusion

Turbulent flow usually happens at faster speed

At turbulent flow, the air is less prone to separation.

At Higher Angle of Attack (AOA), the separation point moves forward

towards the leading edge.

The boundary layer thickens when turbulent flow is formed

From the experiment, shows that the Symmetrical aerofoil is the best

wing shape aerodynamically.



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Appendix and Reference

1. R H Barnard and D R Philpott. (2004)(3 rd Edition) Aircraft Flight . England

Pearson Education Limited

2. http://history.nasa.gov/SP-367/f37htm

3. http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml

4. http://acam.ednet.ns.ca/curriculum/wing.htm

5. David F.Anderson and Scott Eberhardt (2001) Undersanding Flight, New

York(USA) McGraw-hill Companies




/ w w w. c a r t a g e . o r g . l b / e n / t h e m e s / S c i e n ce s / P h y s i c s / M e c h a n i c s / F l u i d M e c h a n i c s /R e a l F l u i d s / B o u n d a r y L a y e r s / B o u n d a r y L ay e r s . h t m )

(

1) http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml)

The stagnation point is the point at which the stream of airmoving toward the wing divides into two streams, one flowingabove and the other flowing below the wing. Air flows faster

above a wing with greater camber since the same amount of



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air has to flow through a narrower space. According toBernoulli's principle, the faster flowing air exerts less pressureon the top surface, so that the pressure on the lower surface ishigher, and there is a net upward force on the wing, creating

lift. The camber is varied, using flaps and slats on the wing inorder to achieve different degrees of lift during takeoff, cruise,and landing.( http://www.enotes.com/earth-science/aerodynamics )

Angle of AttackThe angle at which a wing strikes the air stream.

The ability to create lift is dependent on the airflow remainingsmooth around the airfoil. At zero degrees angle of attack there is

just a small turbulent wake.

At very high angles of attack the separated flow region expands andthe lift is reduced and drag increases. There will be a largeturbulent wake.



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(Introduction to Aerospace)EAS105 -Lab1

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