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WIND TUNNEL TESTING

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Wind Tunnels

Objective

• Accurately simulate the fluid flow about atmospheric vehicles

• Measure -Forces, moments, pressure, shear stress, heat transfer, flow field

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Working of wind tunnel

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WIND TUNNEL LAYOUTS

Closed Return Open Return Double Return Annular Return

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Closed Return(Open Test Section)

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25 to 1 C o n tra c tio nS c ree n s Hig h Con traction W in d T u n n el

T op V iew

D iffu se r

Open Return(Closed Section)

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Double Return

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Annular Wind Tunnel

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TYPES OF WIND TUNNELS

Subsonic Transonic Supersonic Hypersonic Specialty (Automobiles)

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SUBSONIC TUNNELS

Low speed wind tunnels are used for operations at very low mach number(M<0.5), with speeds in the test section up to 480 km/h They may be of open-return type with air moved by a propulsion system.

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80X120 NASA AMES

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80x120 Wind Tunnel NASA Ames

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12 Foot Pressure Tunnel

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TRANSONIC WIND TUNNELS High subsonic wind tunnels (0.4 <

M < 0.75) or transonic wind tunnels (0.75 < M < 1.2) are designed on the same principles as the subsonic wind tunnels.

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TRANSONIC WIND TUNNEL

Testing at transonic speeds presents additional problems, mainly due to the reflection of the shock waves from the walls of the test section

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8x6 Functions & CapabilitiesThe 8x6 Foot Supersonic Wind Tunnel provides customers with a Facility capable of testing largescale aero propulsion hardware

Relative altitude 1000 - 35000 ft Dynamic Pressure 3.6 - 4.8 x 106/f Temperature 60 - 250oF

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8X6 AT NASA LEWIS

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SUPERSONIC WIND TUNNELS A supersonic wind tunnel is a

wind tunnel that produces supersonic speeds (1.2<M<5) The Mach number and flow are determined by the nozzle geometry.

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HYPERSONIC WIND TUNNELS A hypersonic wind tunnel is

designed to generate a hypersonic flow field in the working section.

The speed of these tunnels vary from Mach 5 to 15.

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AUTOMOBILE WIND TUNNELS External flow tunnels - Used to

study the external flow through the chassis

Climatic tunnels - Used to evaluate the performance of door systems, braking systems etc. under various climatic conditions.

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TYPES OF WIND TUNNEL TESTING Force Test

Force measurement requires a force to be exerted (lift & drag forces so termed force test)

The balance can measure only two forces: lift & drag

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TYPES OF WIND TUNNEL TESTING Pressure Tests

Insert tiny tubes into the model surface or airstream and connect them to a pressure measuring device

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Pressure Test: Lowered pressure over the wing

surface reduced the pressure in the manometer tubes and draws the water level up to a high level

The lower the pressure, the higher the water level goes

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TYPES OF WIND TUNNEL TESTING Flow Patterns

Allow the streamlines of air flow to look at the body’s aerodynamic properties

Tufting allows for the flow pattern visualization

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Flow Patterns

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INSTRUMENTS USED IN WIND TUNNELS 1.Force Balance 2.Static Pressure Measurement 3.Strain gauge 4.Spring Gauge 5.Laser Doppler Velocimetry 6.Laser Sheet

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FORCE BALANCE

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STATIC PRESSURE MEASUREMNT

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STRAIN GAUGE

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SPRING GAUGE

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LASER DOPPLER VELOCIMETRY

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LASER SHEET

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HOW ARE CARS TESTED IN WIND TUNNELS?? It is used to quantify and validate

what is going on aerodynamically to the vehicle by measuring forces exerted on the body through a 6 component balance.

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HOW ARE CARS TESTED IN WIND TUNNELS?? Adding a rear wing to your car might

gain you down force, but a wind tunnel will tell you in fact if it is, how much, and how it affected the overall front to rear balance of your car. 

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HOW ARE CARS TESTED IN WIND TUNNELS?? Each test will output the drag, down

force (front & rear), and side force (front & rear), yaw/pitch/roll moments, in order to see the big picture of what is really happening for any given configuration.

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Few Examples

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COST OF A WIND TUNNEL

A high quality portable vertical wind tunnel will cost you anywhere from 1.6crores to 4.1crores. This type of tunnel can accommodate skydivers as well as tourists.

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WIND TUNNELS IN THE WORLD

1.Altitude Icing Wind Tunnel(Ontario Canada)

2.Wright Brothers Wind Tunnel(MIT Massachusetts USA)

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WIND TUNNELS IN THE WORLD 3.Wind Tunnel at NASA Ames

(World’s Largest USA) 4.Langley Low Pressure

Turbulence Wind Tunnel(NASA Virginia USA)

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REFERENCES

www.wikipedia.com www.nasa.org

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THANK YOU