What is Wind tunnel: Definition and 107 Discussions

Wind tunnels are large tubes with air blowing through them which are used to replicate the interaction between air and an object flying through the air or moving along the ground. Researchers use wind tunnels to learn more about how an aircraft will fly. NASA uses wind tunnels to test scale models of aircraft and spacecraft. Some wind tunnels are large enough to contain full-size versions of vehicles. The wind tunnel moves air around an object, making it seem as if the object is flying.
Most of the time, large powerful fans blow air through the tube. The object being tested is held securely inside the tunnel so that it remains stationary. The object can be an aerodynamic test object such as a cylinder or an airfoil, an individual component, a small model of the vehicle, or a full-sized vehicle. The air moving around the stationary object shows what would happen if the object was moving through the air. The motion of the air can be studied in different ways; smoke or dye can be placed in the air and can be seen as it moves around the object. Coloured threads can also be attached to the object to show how the air moves around it. Special instruments can often be used to measure the force of the air exerted against the object.
The earliest wind tunnels were invented towards the end of the 19th century, in the early days of aeronautic research,
when many attempted to develop successful heavier-than-air flying machines. The wind tunnel was envisioned as a means of reversing the usual paradigm: instead of the air standing still and an object moving at speed through it, the same effect would be obtained if the object stood still and the air moved at speed past it. In that way a stationary observer could study the flying object in action, and could measure the aerodynamic forces being imposed on it.
The development of wind tunnels accompanied the development of the airplane. Large wind tunnels were built during World War II. Wind tunnel testing was considered of strategic importance during the Cold War development of supersonic aircraft and missiles.
Later, wind tunnel study came into its own: the effects of wind on man-made structures or objects needed to be studied when buildings became tall enough to present large surfaces to the wind, and the resulting forces had to be resisted by the building's internal structure. Determining such forces was required before building codes could specify the required strength of such buildings and such tests continue to be used for large or unusual buildings.
Circa the 1960s, wind tunnel testing was applied to automobiles, not so much to determine aerodynamic forces per se but more to determine ways to reduce the power required to move the vehicle on roadways at a given speed. In these studies, the interaction between the road and the vehicle plays a significant role, and this interaction must be taken into consideration when interpreting the test results. In an actual situation the roadway is moving relative to the vehicle but the air is stationary relative to the roadway, but in the wind tunnel the air is moving relative to the roadway, while the roadway is stationary relative to the test vehicle. Some automotive-test wind tunnels have incorporated moving belts under the test vehicle in an effort to approximate the actual condition, and very similar devices are used in wind tunnel testing of aircraft take-off and landing configurations.
Wind tunnel testing of sporting equipment has also been prevalent over the years, including golf clubs, golf balls, Olympic bobsleds, Olympic cyclists, and race car helmets. Helmet aerodynamics is particularly important in open cockpit race cars (Indycar, Formula One). Excessive lift forces on the helmet can cause considerable neck strain on the driver, and flow separation on the back side of the helmet can cause turbulent buffeting and thus blurred vision for the driver at high speeds.The advances in computational fluid dynamics (CFD) modelling on high-speed digital computers has reduced the demand for wind tunnel testing.

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  1. S

    Other Wind Tunnel Research at a Community College

    I'm a student at a community college that was gifted a wind tunnel by a local uni. I'm leading a group of 5+ engineering / science students to refurbish and tune it. The testing chamber is around 12 x 5 x 5 inches, and we have free reign to do anything we'd like. We've had some ideas like...
  2. prithika

    I Effect of vent ratio on the drag coefficient of round parachutes

    For my 12th grade school project, I'm planning to research on the effect of vent ratio on the drag coefficient of round parachutes. My idea was to make small model parachutes and drop them from a height, and derive the drag coefficient after certain assumptions. But I also thought it'd be...
  3. K

    So who here has tried to make a homemade wind tunnel? My first attempt

    Hello all, i posted this on another forum but didn't get much response, I had an 18” centrifugal fan around around and wanted to see if I can push some real air to make a wind tunnel. I'm just a hobbyist, and like to build and modify cars, figured this would be something to look into. Looks...
  4. O

    How do I calculate static and dynamic pressure for a wind tunnel lab report?

    how do I calculate static and dynamic pressure for the wind tunnel lab report, drag force, and lift force? Please, anyone? thank you.
  5. WhiteWolf98

    [Structural Dynamics] How to model a 3D wing as a 2D Wind Tunnel Model

    Greetings Good People, As the title suggests, I'm having some trouble getting to a 2D model. The process is to select an aircraft (or wing model), and model it as a 2D, 2DOF wing-tunnel model. The aircraft I selected was a Cessna 172. This had a tapered wing, which after some calculations and...
  6. J

    How calculate lift/drag using static pressure taps in wind tunnel test?

    An airfoil section in a wind tunnel has many static ports/holes/taps on its upper and lower surface. These static ports can only read static pressure which acts perpendicularly to the local airfoil surface. In place A are static ports that read a pressure value of relative -100 Pa . This...
  7. agnimusayoti

    How to Measure Very Small Differential Pressure in a Subsonic Wind Tunnel

    I assume that air have ##1 kg/m^3## density. Therefore, using Bernoulli equation, on upside and downside of my test object, there is a differential pressure ##\Delta P##: $$\Delta P=0.5*(v_2^2 - v_1^2)$$ From cases: (a) ##v_1 = 1 m/s## and ##v_2 = 2 m/s##, then ##\Delta P = 1,5 Pa## (b) ##v_1 =...
  8. J

    Wall to wall airfoil in a wind tunnel

    Does wall to wall airfoil produce downwash in wind tunnel ?
  9. Aun Muhammad

    Single and Dual-Rotating Propeller Question

    Hoping that someone can explain what the optimum angular displacement between the front and rear propellers actually means here in the following paragraph. It concerns the single-rotation case of the experiment: "Both the eight-blade single- and dual-rotating propellers were mounted in four-way...
  10. Kevin_787

    Wind tunnel calculations (making my own)

    Hey guys, I'm not sure this is necessarily a physics question, so if it's not I'd appreciate it if someone could point me in the right direction; but here goes. I've been giving some thought to building a wind tunnel lately, I realize this won't be cheap on any large scale, but I just want to...
  11. 0

    Simple lift/drag measurements in a wind tunnel

    Hi everyone, I will be conducting wind tunnel tests of a NACA 0012 airfoil to obtain values of lift and drag in a low-speed wind tunnel (approx M = 0.1). I am looking for a really simple way of measuring these forces. Does anyone know of ways to achieve this? I am aware of force balance...
  12. K

    Lift and Drag force in a Wind Tunnel

    Hello guys, I am trying to calculate the lift force and drag force in a wind tunnel at my school as a part of a project that i am doing. I am varying the length of the airfoils and trying to measure the lift force and drag force. I have 3-d printed 7 airfoils. However, I am not able to find any...
  13. M

    How can i calculate the velocity in a wind tunnel

    Ive done some wind tunnel experiments for a wing design i made, the wind tunnel was set to 50% power and the incidence angle was increased from -2 to 14 at 2 deg increments, how do i calculate the velocity for each recording? I've done this before but I am just having a mental block on...
  14. T

    How accurate is my wind tunnel for testing RC plane wings?

    Hi everyone, I am new and I hope I'm putting this in the right section. I am currently a Sophomore in High school and I am building a wind tunnel. It's not for a class but rather its is like an independent study. I have been into planes pretty much all my life and I am hoping to get a pilots...
  15. zehkari

    Calculating Drag Coefficient from Wind Tunnel Data

    Homework Statement Using a wind tunnel to measure force and velocity at different drive %, we obtained some data for drag. We used one dimpled sphere and one smooth sphere. There are a couple of questions I am stuck on. "The force you have measured is known as the drag force and can be...
  16. S

    Creating a Wind Tunnel Simulation: Where to Begin?

    Hi everyone, I am currently doing my Computer Science A-Level project and I'm thinking of simulating a wind tunnel but I am also having a really hard time figuring out how to start. I am programming it in Visual Basic (XNA) and using Blender for models. Could anyone guide me in the right...
  17. H

    How to choose a fan for open circuit wind tunnel?

    Hi all, I am trying to design a open circuit wind tunnel, and I've got to the point where a fan should be selected. However, I am not familiar with fans at all, so I am wondering if you could help me! My understanding is that the fan selection process is quite similar to the pump selection...
  18. D

    I Build my own virtual wind tunnel

    I want to build a computer simulated wind tunnel. I have experience building physics simulators. I undersand that there are already some existing free wind tunnel simulators out there, but do they work at supersonic speeds? I want to predict the drag coefficient of various rockets and bullets at...
  19. M

    Aircraft model in a wind tunnel and the full size version

    I try to understan this article: https://en.wikipedia.org/wiki/Reynolds_number What does "... such as between an aircraft model in a wind tunnel and the full size version." mean? Why cannot we use a full size version in a wind tunnel or why cannot model be full size? Thank you.
  20. B

    Wind Tunnel -- initial testing speed?

    Hi! I would like to submit a model glider to a CFD wind tunnel so I can determine what would be its optimum glide ratio and forward speed at this incidence. I am not supposed to know in advance the range of speed this glider can fly (between stall and structural damage), so the speed I will...
  21. FQVBSina

    Pressure and flow speed relationship in wind tunnel

    I need 250 m/s of airflow speed in a wind tunnel. I can assume for this purpose, the test section of the wind tunnel has uniform flow. However, the wind tunnel can only generate a flow rate of 100 m/s but the pressure can be increased. I am drawing a blank on how could a generic boundary layer...
  22. F

    Exploring Wind Tunnel Data Collection Methods for Physics Coursework

    I'm nearly at the end of my preliminary testing for a wind tunnel in my A2 physics coursework. My question for my project so far is: "Do different shaped objects exhibit different properties under the influence of high speed air". For my coursework I need to measure or observe something to get a...
  23. O

    Why Does Bernoulli's Equation Apply to Wind Tunnels?

    I hope this question doesn't have too obvious of an answer. Basically, I still cannot grasp why Bernoulli's equation applies for wind tunnels and pitot-static probes. According to my textbook ("Introduction to Flight" by Anderson), Bernoulli's equation holds only when comparing two points...
  24. MdAsher

    Understanding Fluid Dynamics of a Flying Frisbee

    Hi All, I'm hoping to work on deriving the governing fluid flow equations for a frisbee in flight theoretically and then to test it on a wind tunnel, and compare results. If u could please help on how do i apply/derive the necessary equations. Respectful Regards
  25. BP Finn

    Wind Tunnel Help: Building a Simple Fan Setup

    Hi, this is my first post. I teach high school physics and am trying to build a simple wind tunnel. For my first attempt I used a Utilitech high capacity 20 inch fan (nominal 6800 CFM) but the resulting air speed was disappointing – only 4.8 m/s. What type of fan would be better? I was...
  26. yangshi

    Choked flow out of air compressor and wind tunnels

    I posted this on Eng-tips and no replies yet:( I'm trying to design an as-simple-and-cheap-as-possible supersonic wind tunnel using an air compressor (this even possible? given the energy losses from shock waves...). I have access to a Porter-Cable 150psi, .8hp air compressor. Questions: 1...
  27. S

    Searching for a 3D Wind Tunnel App: PC-Compatible?

    I'm looking for a two element 3D wind tunnel app. Any out there that will run on a PC?
  28. Jam 1959

    Automotive Wind tunnel to do smoke testing of my Formula Vee racing car

    Hello.I need help with wind tunnel.The test section is 2m x 2.5 m x 5 m long.How do I work out size of inlet cone.Thanks in advance
  29. Mr.hev

    Calculating Reynolds number for a wind tunnel

    Hi All! as you can see I'm new here! i signed up in order to ask for a wee bit of help with my thesis! (now don't get me wrong I am not exactly asking anyone to write it for me!) I've found myself at a small bit of a loose end here, as a mechanical engineering student i am perfectly capable of...
  30. H

    Calc Oblique Shock Angle for Supersonic Flow 0-5 Degrees

    Is there an equation to calculate the oblique shock angle for supersonic flow when the given angle of attack is greater than 0, but less than the half angle? In my particular practical experiment, the half angle of the aerofoil is 5 degrees, so want to get a variety of figures between 5 and -5...
  31. C

    Calculating Force of Wind on Flat Object: A Skydiving Coach's Guide

    I am a skydiving coach and I am trying to figure out how many pounds of force wind moving approximately 120 mph has on something with a surface area of 25 square inches. I know turbulence and compression play into it as we'll but I just want a general formula to figure it out. The object is...
  32. T

    Using Bernoulli's Equation to find pressure in a wind tunnel

    Homework Statement A wind tunnel is designed to draw in air from the atmosphere and produce a velocity of 100m/s in the test section. THe fan is located downstream of the test section. What pressure is to be expected in the test section if the atmospheric temperature and pressure are -20C...
  33. P

    Drag and Lift Sensors for a Subsonic Wind Tunnel

    Hey everyone, I'm a student working on building a wind tunnel with some classmates. I'm in charge of figuring out the drag and lift force sensors. I'm currently looking these two components: http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2128260_-1...
  34. A

    Matching Reynolds Number in Scale Model Wind Tunnel Testing

    For my senior design project, I have to reduce the aerodynamic drag of a truck and trailer. I am doing CFD simulations and wind tunnel testing. The dimensions of the wind tunnel (test section) are 94 in long, 13.5 in tall and 20 in wide and a cross-sectional area of 270 in^2 and it could go up...
  35. A

    Building a Homemade Wind Tunnel for High School Project | Aerodynamics DIY

    Hi guys! I am doing a project for my High School, here in Spain, that is obligatory for everyone. As a love everything related with planes and aerodynamics I've decided to create this wind tunnel. Is approximately 2,15 meters long and it weights around 10 kilos. It is made 100% of wood and it...
  36. O

    Experimental Measurements in Wind Tunnel

    Hello everyone, the forum looks great and I have been reading it for a long time, but I have only registered. I am writing this post because I have to analyse two flow fields in a wind tunnel. 1) The first flow is generated from a helicopter blade, with Re=2000000, Mach=0.92 and...
  37. A

    Can a wind tunnel simulate a scramjet?

    Can a wind tunnel get up to scramjet speeds; ie. Mach 6-12?
  38. Q

    Calculating Load for a Mini Wind Tunnel?

    Hey guys, so I'm building a mini wind tunnel and I would like to calculate the new RPM,HP and Torque since the propeller will act as a load and change the specs of the motor(note I'm using a air wrench as the motor as it's all I had around and have disabled the impact motion) the current specs...
  39. J

    Where Can I Find UK Companies That Provide Wind Tunnel Model Mold Services?

    Hi, I am currently researching methods available for manufacturing a half-span wing model (approx 0.5m span, low sweep delta wing of varying cross section) to be used in wind tunnel experiments. A recent paper suggested the use of epoxy and micro glass beads injected into an aluminium mold...
  40. D

    Repeating Water Tunnel Studies in Wind Tunnel

    Is there any significance in repeating a water tunnel study in a wind tunnel? If so, would the results be publishable or would it just be considered repetition of a previously published water tunnel study?
  41. G

    Creating controlled turbulence in a home-built wind tunnel

    Hi, I have built an 8' long wind tunnel for use in an experiment to test the effects of turbulence on several variables. However, seeing as this is an educational-level/novice wind tunnel with a fan rating of ~1800 cfm the wind speeds only really go up to ~10 mph. From my understanding, this...
  42. A

    How can I achieve 30mph in my homemade wind tunnel?

    Hey everybody, I have built a 7' wind tunnel. The test section is 7''x7'' and 24" long. The diffuser opens to 22''. I would like to achieve around 30mph through the test section. I am having trouble finding a fan that can meet that need. I have looked into using an electronic radiator...
  43. G

    Strain gage to measure drag in a wind tunnel?

    How would a strain gage be set up (on top of the model? around the sting?) to measure drag? I don't quite understand the connection between the force of drag and some sort of compression/tension force...? Thanks for the clarification.
  44. shinnsohai

    Designing a Wind Tunnel: Homework Assignment and Bernoulli Principle Explanation

    Homework Statement Recently I've been given an assignment Build a Wind Tunnel(That can generated wind speed of 20m/s) -Izzit the chamber(whole tunnel) must be sealed ? -The material of the wind tunnel must be transparent(something like plastic?)on the test section?? Homework...
  45. R

    Wind Tunnel Design Question Re: Test Section and Diffuser/Fan Size

    Hello, My name is Ryan and I'm a volunteer instructor with the local Royal Canadian Air Cadet squadron. I'm looking for ways to try and make the kids' aviation lessons more interactive and hands on, and so I've decided I'd like to build them a small wind tunnel, purely for flow visualization...
  46. L

    Wind Tunnel Power Requirements

    I am designing a wind tunnel for my final year project. I am am now a little lost at the power requirements area. To select a fan, i understand that i have to overcome the pressure drops through out the tunnel by choosing a fan that has a higher pressure rise. So far i have figured out that i...
  47. M

    Calculating Reynolds number in wind tunnel

    when calculating a Reynolds number for an obstacle in wind tunnel Re = air density * air velocity * D / Dynamic viscosity D here is the characteristic length of the immersed body ( frontal length ) 2 dimensional problem Or the Hydraulic diameter which relates the tunnel dimensions to the...
  48. S

    The single strut in wind tunnel test

    I will do research on the vertical single strut. i want to ask if there is something interesting to study?
  49. B

    Definition wind tunnel blockage ratio

    Hello, I’m designing a 2D wind tunnel model for my master thesis. It will be a profile equipped with a fixed hinged trailing edge flap. I’m going to measure at different angle of attacks and different flap settings at low speeds (about 70 to 100 m/s). The aim is to measure steady and unsteady...
  50. V

    What can I do to make my wind tunnel testing project more complex?

    Hello all, I'm in my final year of engineering so I'm required to complete a thesis as part of that. My topic is to investigate the wind loading on a typical conveyor belt + truss arrangement, because there's a lot of uncertainty in industry about drag coefficients etc. I've attached a model...