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Questions tagged [wind-tunnel]

A wind tunnel is a tool used in aerodynamic research to study the effects of air moving past solid objects. A wind tunnel consists of a tubular passage with the object under test mounted in the middle. Air is made to move past the object by a powerful fan system or other means.

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Why would there be a drag discrepency when simulating transonic flow over scaled CRM geometry?

I have a discrepancy when simulating a wind tunnel experiment of a 2.7% scaled NASA CRM geometry as used in the wind tunnel. I am trying to replicate exactly the wind tunnel model and flow conditions ...
Sharan S Pant's user avatar
13 votes
4 answers
3k views

Why does this curved wind tunnel rotate?

Why does this curved wind tunnel rotate, why is it not just curved? A curved wind tunnel has a radial pressure gradient, but this pressure gradient doesn't exist in a real turn, so how do you get ...
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What type of probe can measure induced drag in the wake?

Induced drag can be measured from velocity preturbation in Treffz plane. In Treffz plane what velocity direction is important for induced drag, vertically down, lateral(horizontal, "spanwise&...
user707264's user avatar
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What weather conditions have been tested with a wind tunnel?

If I want to know how my aircraft component performs in different atmospheric conditions, I might want to test it in a wind tunnel. What sorts of weather conditions have been tested in a tunnel? I am ...
Anonymous Physicist's user avatar
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125 views

Aerofoil selection for a Horizontal turbine [duplicate]

I'm currently having a bit of an issue selecting the type of aerofoil I would want to use in my ridge mounted wind turbine honours project. I want to select a high lift generating aerofoil at low ...
Henry's user avatar
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2 answers
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If an aerofoil is placed in a narrow wind tunnel, how will that affect the lift it produces?

This is NACA 0000 aerofoil: This is just a straight line - roughly what a paper plane's aerofoil section looks like (I chose this aerofoil for its simplicity). If we put this aerofoil in a wind ...
Aditya Sharma's user avatar
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2 answers
120 views

is it necessary for the velocity distribution profile over a flat plate to have that kind of parabolic shape?

A wind tunnel boundary layer experiment was done for a flat plate with 5 stagnation probes distributed horizontally (each probe has 5 vertical sensors) and a variable flap, for 2 different free stream ...
I.ham's user avatar
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3 answers
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Does Cd number change at different speeds during wind tunnel testing?

When meassure Cd or Cl of airplane/car in wind tunnel, does number change at different speeds, for example at 100km/h compare to 250km/h? If yes,how much? I know from theory that coefficents change ...
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How can I calculate the TOTAL drag of the ENTIRE airplane?

I have an aircraft similar to a Cessna 172 and am using a virtual wind tunnel software (flowdesign) to get a drag estimate. I import the airplanes 3D model and I get around 2240 lbs of drag with a ...
Vincent Cerowski's user avatar
2 votes
1 answer
146 views

What is the modern approach to extract vehicle system responses to control input? [closed]

What is the modern approach to extract vehicle system responses to control input? Is everything thrown into a CFD simulation and the responses recorded or is something else done? Are wind tunnels ...
FourierFlux's user avatar
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2 answers
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How calculate lift/drag using static pressure taps in wind tunnel test?

An airfoil section in a wind tunnel has many static taps on its upper and lower surface. These static ports can only read static pressure which acts perpendicularly to the local airfoil surface. In ...
user707264's user avatar
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How can I make a serious wind tunnel?

I am looking for specifics of building and the operation of low speed wind tunnels, but most diy wind tunnels on internet are improved versions of science fair projects at best. What would I need to ...
gungun sharma's user avatar
5 votes
1 answer
208 views

How do engineers estimate the aerodynamic effects caused by jet engines or propellers in wind tunnels?

When aircraft models are tested in wind tunnels they don't seem to have engines or propellors on them. So how do engineers get correct parameters from the experiments? Do they just seal the air inlets ...
Mridul's user avatar
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How should I attach an aircraft model in a wind tunnel when testing wind gust/yaw stability?

Where should I attach the rod to the aircraft model when simulating wind gust /weather vane effect in wind tunnel testing? At the center of gravity, behind the CG, in front of the CG...?
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Why do wind tunnels not have oval turns?

Why do wind tunnel not have oval turns to reduce energy which is lost in sharp 90 degree turns and decrease turbulence? Wind tunnel with oval turns: Wind tunnel with 90 degree turns:
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Fan power for 3x3m wind tunnel? [closed]

How much power do I need for 3x3m wind tunnel,with airspeed up to 200km/h? Some formula for calculation?
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1 vote
1 answer
263 views

In wind tunnel testing "same Mach number" is not "same airspeed"?

Wikipedia: "Mach number: the ratio of the airspeed to the speed of sound should be identical for the scaled model and the actual object (having identical Mach number in a wind tunnel and around ...
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1 vote
3 answers
238 views

Wing vs wall to wall wing,total drag comparation at same AoA?

Compare total drag of wall to wall wing vs wing(open tips) in wind tunnel,AT SAME AoA. My first intuition is that wall to wall wing has higher pressure drag at outward parts of wing,because side-walls ...
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2 votes
1 answer
272 views

Can I measure induced drag with a simple wind tunnel test?

Device can measures total drag force and lift of wing for given AoA and airflow speed. Wing both wingtips are far away from side walls. Airflow speed is constant all the time:50m/s TOTAL DRAG=...
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6 votes
2 answers
825 views

Do wall-to-wall airfoils produce induced drag?

The walls in a wind tunnel stop air leakage around the outboard sections of an airfoil, and the pressure distribution at the center section is the same as at the outboard sections (if we neglect ...
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2 votes
1 answer
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Wind tunnel- test section design question? [closed]

1)Why test section room is so so big,is this because to reduce interfrence between test object and walls? 2)Is test section room open to outside atmopsheric pressure or must be 100% air proof? 3)How ...
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4 votes
1 answer
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Can a wind tunnel simulate airflow when a vehicle goes around a curve?

In real life, airflow in a turn is curved, how does a wind tunnel simulate this condition? If we just yaw the test object at some angle in wind tunnel, do we simulate the airflow in correct way?
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17 votes
1 answer
2k views

What are some specific benefits of cryogenic wind tunnels?

What are some benefits to using a cryogenic wind tunnel over a more traditional one? Are there certain aerodynamic properties or principles that are better studied at low temperatures?
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2 votes
1 answer
174 views

is there difference b/w moving object in a fluid and static object in a moving fluid?

wind tunnel is usually based on static object in a moving fluid, but wouldn't stationary/semi wind inevitably fill the tunnel after collision, but in the real world the moving object is always meeting ...
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1 answer
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Which type of fan is better for wind tunnel testing?

I would like to build a small wind tunnel to test a miniaturized wing/airplane. I have two options, using axial blower (picture 1) or using centrifugal blower (picture 2). The first will be the wind ...
AirCraft Lover's user avatar
2 votes
0 answers
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Flow Straightener location

Do wind tunnels with flow straightener after the flow contractors have slower flow velocity compared to a wind tunnel with the flow straightener right after the fan? Note: I'm assuming the same fan is ...
itisyeetimetoday's user avatar
0 votes
2 answers
516 views

How to measure wind speed in a wind tunnel

I'm currently building a wind tunnel that moves air at hundreds of meters per second. How do I cheaply measure the wind speed?
itisyeetimetoday's user avatar
3 votes
2 answers
591 views

What is the explanation of this airfoil phenomenon? Why the air from below the leading edge's tip deflected up?

I have difficulties to understand this air phenomenon, why the air from below the leading edge's tip (from below the horizontal line) is deflected up and not just follow the bottom wing's surface? ...
AirCraft Lover's user avatar
3 votes
2 answers
1k views

How to artificially increase the Reynolds number in a wind tunnel?

I'm currently scaling down a model 64 times for a wind tunnel analysis, where I'm measuring drag force (for drag coefficient) and lift force (for lift coefficient). However, I read that scaling down ...
itisyeetimetoday's user avatar
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1 answer
424 views

Pitching moment as a pure moment and its measurement with a homemade force balance

In mechanics, we learn that a force $F$ acting at a certain application point $P$ can exert a torque (also called moment of the force) about another arbitrary point $Q$ in the plane, i.e. $\tau= F \...
Brett Cooper's user avatar
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1 answer
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Which propeller configuration is the one that generates the least turbulent flow in a wind tunnel?

I looked at the post here but still have some questions Why are push-propellers so rare, yet they are still around? This is along the same idea but the answers are not too helpful either. Pros and ...
Bwebb's user avatar
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2 answers
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Where can you find wind tunnel visualization data online?

I was wondering if there was a repository of flow visualization results somewhere online, preferably of wing sections categorised in some manner.
dipak's user avatar
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1 answer
117 views

Where should the support points be for testing a model wing in a wind tunnel?

When testing a certain wing profile inside a wind tunnel where should the model, small scale wing be supported? Should the support be under the center of mass of the wing or under the aerodynamic ...
Brett Cooper's user avatar
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1 answer
2k views

How do we derive Lift Coefficient of an airplane's wing?

In many references I read that lift coefficient ($C_l$) is a product of wind tunnel test. But many times I read the formula to calculate the coefficient of lift. From the lift equation, $$L=\frac{1}{2}...
AirCraft Lover's user avatar
1 vote
1 answer
1k views

Why do we see a reduction in temperature in a wind tunnel by increasing the velocity, but in a real flight it's the opposite?

In a real flight, when the speed of an aircraft increases, we see an increase in temperature too. So that at high Mach numbers the surfaces of the aircraft will be very hot. Now I have encountered ...
Ramin.A's user avatar
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2 votes
1 answer
581 views

Lift and Drag Coefficients using load cell data

I have a MAV and I need to find out the lift and drag coefficients for the wing and tail. I am not available with a wind tunnel so I will be using a load cell along with a separate wind source. Now I ...
Mani's user avatar
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11 votes
2 answers
7k views

How is windspeed scaled in wind-tunnel tests?

Let's say you have a scale model that is 1:10th the size of the real thing. You want to test this in a wind-tunnel. Do you also scale down the windspeed 10x? Why or why not? I would think it has to ...
DrZ214's user avatar
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3 votes
3 answers
179 views

How is the centre of lift estimated for airplane models before they are being mounted in a wind tunnel?

They mount the airplane models or parts of an airplane like just a wing, or a rudder in wind tunnels to test their drag and lift, stability, etc. How do they know where to hang it from or mount it on....
kamran's user avatar
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5 votes
2 answers
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Does the Reynolds number on a smaller model need to match the one of the original aircraft?

1.Airbus 380-800 : The overall length of it , is 72.72 m and its cruise speed is 903 km/h. Based on the mean chord of wing , its Reynolds number in cruise phase is around 75 millions. Now , a 1/18 ...
alireza abbassi's user avatar
5 votes
4 answers
2k views

Can this design provide more lift force than thrust from engine?

The problem is depicted in the picture: Generally, why we don't use engine blow wings to fly? Can we use wind-tunnel-like wing to generate lift force? Can it generate more lift than thrust? If it ...
Libo Liu's user avatar
1 vote
1 answer
536 views

Is there an analytical description of the NACA 642-015A profile?

While searching for symmetric profiles I stumbled across different definitions (point-clouds) of the NACA 642-015A profile. http://airfoiltools.com/airfoil/seligdatfile?airfoil=n64015a-il http://www....
rul30's user avatar
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4 votes
1 answer
1k views

Does zero-lift angle of attack depend on Reynolds number?

In this post I read that, due to viscous effects, the $C_{l}$ at a given angle of attack increases slightly with the Reynolds number but it seems that it just happens near the stall angle of attack. ...
abcd's user avatar
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How to calculate the drag on an airfoil from momentum equation (Fundamental of Aerodynamics 5th edition, J.D.Anderson)?

If you got the book, please read 2.6 section (page 135). Here is my sumary of this section: An airfoil in a wind tunnel (wingtips were butted against both sidewalls of wind tunnel). The control ...
Dat's user avatar
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2 votes
3 answers
618 views

What is the practical usefulness of a small home made wind tunnel?

Is a small wind tunnel, like in the video, of any value for building planes able to carry a man? Can the lift and drag, corresponding to a scaled down wing (or segment of a wing) introduced in such a ...
Robert Werner's user avatar
9 votes
3 answers
12k views

How are wind tunnels used with scale models?

This answer introduced me to the problem of using scaled models in a wind tunnel. How are wind-tunnels used in practice (for modelling the performance of subsonic airplanes)? In particular: Do they ...
ChrisW's user avatar
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5 votes
1 answer
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What was the first supersonic wind tunnel?

What was the world's first supersonic wind tunnel? Who built it and how did it work? All I've found so far is this Wikipedia article that says: By the end of the war, Germany had at least three ...
DrZ214's user avatar
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1 answer
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What aspect ratio is best for Wind Tunnel Testing an aerofoil with Small Additives? [closed]

Vortex generators will be 3D printed on a panel, which is then to be slotted onto a foam aerofoil to be tested in the wind tunnel for performance and flow physics. What I want to know is which aspect ...
Tristan Júnny Tse's user avatar
2 votes
1 answer
739 views

Are these pressure and velocity distributions calculated by CFD simulation correct?

I am simulating wind tunnel tests for a NACA64210 airfoil with the following conditions: $P_\infty=101300$ $Pa$ ; $\rho = 1.23$ $kg/m^3$ ; $U_\infty = 29.99$ $m/s$ I performed the simulation with ...
user3780731's user avatar
4 votes
1 answer
6k views

How should the pressure coefficient distribution from a wind tunnel experiment be interpreted?

I'm doing a wind tunnel experiment and I'm trying to plot the pressure coefficient distribution for the upper and the lower surfaces of an airfoil based on experimental data. The airfoil chord is 150 ...
user3780731's user avatar
17 votes
2 answers
4k views

Why are wind tunnel models sometimes placed upside down?

Sometimes in wind tunnel tests, models are suspended upside-down: Image obtained from DNW - Interference corrections Image obtained from this Youtube video of testing at AEDC Image obtained from ...
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