wind tunnel inroduction

7/26/2019 Wind Tunnel Inroduction

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Gayon Jio Ross Godfrey S.

Oarde Kevin Victor L.

Zaide John Chester A.

AE 412

6/17/2013

Wind unnel


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Frank Wenham

Benjamin Robins

George Cayley

Osborne Reynolds

Hiram Maxim

Wright Brothers


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Introduction

What is a Wind Tunnel?

AE 412Introduction Classifications Elements Types Shapes Flow Visualization

a facility that provides a controllableflow field for investigating variousflow phenomena and testing

aerodynamic models a tool used in aerodynamic research

to study the effects of air moving pastsolid objects

*** Advantage: experiments can be performed under well-controlledflow 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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n Aeronautical Wind Tunnelsn Automobile Tunnels

n Aeroacoustic Tunnels

Classifications of Wind Tunnel

Introduction Classifications Elements Types Shapes Flow VisualizationAE 412


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Aeronautical Wind Tunnels

High Reynolds Number TunnelsPressurized TunnelsHeavy Gas TunnelsCryogenic Tunnels

High-altitude Tunnels

V/STOL TunnelsSpin Tunnels



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Tunnels are also classified by flow speed:Subsonic (M


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Wind tunnels may also be classified according to theirair pressure: atmospheric

variable- densityor their size: ordinary full-scale



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Elements of a Wind Tunnel



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straightens the airflow

*** The less turbulence there is, thebetter the wind tunnel will simulate

actual flying conditions

usually includes a honeycomb flowstraightener and wire mesh

smoothing screens that produce asmooth airflow; effective at reducingswirling currents in the tunnel airflow



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*** purpose: take a large volume of low-velocityair 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 thedesired velocity, sensors measure

forces, such as lift and drag, on thetest 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 aplane through the air.



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Shapes of Test Section

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

AE 412Introduction Classifications Elements Types Shapes Flow Visualization


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where the air coming out of the test sectionslows down prior to exhausting orrecirculating

a device to lower the air flow speed,

consequently reduce the pressure loss dueto friction



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provides the force that causes air to movethrough the tunnel

*** Fan drive: provide apressure increase offlow, to overcome thepressure loss in the

tunnel circuit.



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17/26Introduction Classifications Elements Types Shapes Flow VisualizationAE 412


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Types of Wind Tunnel

Closed-typeOpen-type


Blowdown

Shock Tube


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Open-type Wind Tunnel

also called an Eiffel tunnel

open on both ends and draws airfrom the room into the test section



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Advantages

Low construction cost.Superior design for propulsion and smokevisualization. There is no accumulation of exhaustproducts in an open tunnel

Disadvantages

Poor flow quality possible in the test section

High operating costsNoisy operation



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Closed-type Wind Tunnel

also called an Prandtl tunnel or Gottingen tunnel

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



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Advantages

Superior flow quality in the test sectionLow operating costsQuiet operation

Disadvantages

Higher construction cost

Inferior design for propulsion and smoke visualizationHotter running conditions than an open return tunnel



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has a high pressure vessel upstream of the testsection and a low pressure reservoir downstreamof the test sectionused for supersonic testing.

Blowdown Wind Tunnel

used for hypersonic testing

Shock Tube



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Advantages

High Mach capability

Lower construction and operating costs.Superior design for propulsion and smoke visualizationSmaller loads on model during startup because of fasterstarts

Disadvantages

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 widerange of temperatures and pressures that are difficultto obtain in other types of testing facilities;

are also used to investigate compressible flow

phenomena and gas phase combustion reactions

Shock Tube


Fl Vi li ti


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Flow 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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QualitativeSmokeTuftsEvaporating SuspensionsOil

FogSublimation

Quantitative

Particle Tracking VelocimetryParticle Image VelocimetryLaser Speckle Velocimetry

OpticalShadowgraphSchlieren PhotographyInterferometry


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Shadowgraph-

Schlieren Photography

Inferometry

Optical Methods


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Smoke-

Tufts-

Oil-

Qualitative Methods

Evaporating Suspensions

Fog-


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Quantitative Methods

Particle Tracking Velocimetry

Particle Image VelocimetryLaser Speckle Velocimetry

wind tunnel inroduction

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