Gayon, Jio Ross Gayon, Jio Ross Godfrey S. Godfrey S.

Oarde, Kevin Victor L.Oarde, Kevin Victor L.Zaide, John Chester A.Zaide, John Chester A.

AE 412AE 4126/17/20136/17/2013

Wind TunnelWind Tunnel

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Frank WenhamFrank Wenham

Benjamin RobinsBenjamin RobinsGeorge CayleyGeorge Cayley

Osborne ReynoldsOsborne ReynoldsHiram MaximHiram Maxim

Wright BrothersWright Brothers

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IntroductionIntroduction

What is a Wind Tunnel?

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a facility that provides a controllable flow field for investigating various flow phenomena and testing aerodynamic models

a tool used in aerodynamic research to study the effects of air moving past solid objects

*** Advantage: experiments can be performed under well-controlled flow circumstances compared to open environment experiments

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National Full-Scale Aerodynamics Complex ,

NASA Ames Research Center, United States

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Aeronautical Wind Tunnels Automobile Tunnels Aeroacoustic Tunnels

Classifications of Wind TunnelClassifications of Wind Tunnel

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Aeronautical Wind TunnelsAeronautical Wind Tunnels

High Reynold’s Number Tunnels Pressurized Tunnels Heavy Gas Tunnels Cryogenic Tunnels High-altitude Tunnels

V/STOL Tunnels Spin Tunnels

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Tunnels are also classified by flow speed:Subsonic (M<.8),Transonic (.8<M<1.2),Supersonic (1.2<M<5.0), orHypersonic (M>5.0)

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Wind tunnels may also be classified according to their air pressure:atmosphericvariable- densityor their size:ordinaryfull-scale

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Elements of a Elements of a Wind TunnelWind Tunnel

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straightens the airflow*** The less turbulence there is, the better the wind tunnel will simulate actual flying conditions

usually includes a honeycomb flow straightener and wire mesh smoothing screens that produce a smooth airflow; effective at reducing swirling currents in the tunnel airflow

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*** purpose: take a large volume of low-velocity air and reduce it to a small volume of high-velocity air

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models of wings or planes are placed here

*** As airflow is brought to the desired velocity, sensors measure forces, such as lift and drag, on the test article.

Lift is the force on the wing opposite the force of gravity. Lift holds a plane in the air.

Drag is the force on the wing in the direction of the airflow. An engine must overcome this force to move a plane through the air.

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Shapes of Test SectionShapes of Test Section

Rectangular (General Purpose) Circular (Axisymmetric Model) Elliptical (Aircraft Model)

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where the air coming out of the test section slows down prior to exhausting or recirculating

a device to lower the air flow speed, consequently reduce the pressure loss due to friction

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provides the force that causes air to move through the tunnel

*** Fan drive: provide a pressure increase of flow, to overcome the pressure loss in the tunnel circuit.

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Types of Wind TunnelTypes of Wind Tunnel

Closed-type Open-type

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Blowdown Shock Tube

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Open-type Wind Tunnel Open-type Wind Tunnel

also called an Eiffel tunnel

open on both ends and draws air from the room into the test section

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AdvantagesAdvantages

Low construction cost. Superior design for propulsion and smoke

visualization. There is no accumulation of exhaust products in an open tunnel

DisadvantagesDisadvantages

Poor flow quality possible in the test section High operating costs Noisy operation

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Closed-type Wind Tunnel Closed-type Wind Tunnel

also called an Prandtl tunnel or Gottingen tunnel

*** Air is conducted from the exit of the test section back to the fan by series of turning vanes; air is returned to the contraction section and back to the test section; air is continuously circulated

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AdvantagesAdvantages

Superior flow quality in the test section Low operating costs Quiet operation

DisadvantagesDisadvantages

Higher construction cost Inferior design for propulsion and smoke visualization Hotter running conditions than an open return tunnel

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has a high pressure vessel upstream of the test section and a low pressure reservoir downstream of the test section

used for supersonic testing.

Blowdown Wind TunnelBlowdown Wind Tunnel

used for hypersonic testing

Shock TubeShock Tube

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AdvantagesAdvantages High Mach capability Lower construction and operating costs. Superior design for propulsion and smoke visualization Smaller loads on model during startup because of faster

starts

DisadvantagesDisadvantages

Shorter test times require faster (often more expensive) instrumentation.

Need for pressure regulator valves. Noisy operation.

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used to study aerodynamic flow under a wide range of temperatures and pressures that are difficult to obtain in other types of testing facilities;

are also used to investigate compressible flow phenomena and gas phase combustion reactions

Shock TubeShock Tube

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Flow VisualizationFlow Visualization aids the people to see the movement of air while

inside the wind tunnel used to make the flow patterns visible

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Qualitative Smoke Tufts Evaporating Suspensions Oil Fog Sublimation

Quantitative Particle Tracking Velocimetry Particle Image Velocimetry Laser Speckle Velocimetry

Optical Shadowgraph Schlieren Photography Interferometry

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Shadowgraph-

Schlieren Photography

Inferometry

Optical MethodsOptical Methods

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Smoke-

Tufts-

Oil-

Qualitative MethodsQualitative Methods

Evaporating Suspensions

Fog-

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Quantitative MethodsQuantitative Methods Particle Tracking Velocimetry Particle Image Velocimetry Laser Speckle Velocimetry