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21 votes
Accepted

What are some specific benefits of cryogenic wind tunnels?

Short answer: A cryogenic tunnel works by taking advantage of the different properties of nitrogen gas at cryogenic temperatures as compared to the properties of air at normal ambient conditions (...
Peter Kämpf's user avatar
14 votes

Why does this curved wind tunnel rotate?

While superficially similar, this curved windtunnel solves a very different problem from a straight windtunnel. A straight windtunnel is used to study steady flight without needing a very long ...
Sanchises's user avatar
  • 13.4k
9 votes

Why does this curved wind tunnel rotate?

Here you'll find his paper about the wind tunnel. Apparently the rotation has been introduced in order to compensate for the Coriolis effect.
sophit's user avatar
  • 13.5k
8 votes
Accepted

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

The aerodynamic coefficients $c_l,c_d,c_m$ are in general functions of the angle of attack $\alpha$, Reynolds $Re$ and Mach number $Ma$. For your experiments, since you are operating in a very low $...
ares's user avatar
  • 614
8 votes

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

Because there is no free lunch. A single wing behind a propeller or a fan can see some amount of performance gain from being in the propeller's slipstream, but, when you start stacking multiple wings ...
Marius's user avatar
  • 3,671
8 votes

Does the Reynolds number on a smaller model need to match the one of the original aircraft?

In wind tunnel testing you need to match several similarity parameters; the most well known are the Reynolds number and the Mach number. Since the Reynolds number depends on flow speed, viscosity and ...
Peter Kämpf's user avatar
8 votes

How is windspeed scaled in wind-tunnel tests?

In order to achieve the same flow conditions, you need to match several similarity numbers. The most important one expresses the ratio of inertial forces to viscous forces within a fluid and is called ...
Peter Kämpf's user avatar
6 votes

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

Trip strips will approximate a higher Reynolds number in the sense that you get turbulent flow at a lower Reynolds number, but they will not increase the Reynolds number themselves. You will have ...
zaen's user avatar
  • 443
6 votes
Accepted

Do wall-to-wall airfoils produce induced drag?

A wall-to-wall wing in a windtunnel should best be compared to one in ground effect and not as a segment of an infinite wing. Both are similar since the infinite wing will be infinitely close to the ...
Peter Kämpf's user avatar
6 votes

Why does this curved wind tunnel rotate?

Key point from another related answer: A stationary curved windtunnel would not be the same, because now the air mass needs to curve. This introduces very different phenomena. Perhaps easiest to ...
quiet flyer's user avatar
  • 22.7k
5 votes

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

Fist, I find it odd that your fan lists its thrust in the unit of a mass. Thrust should be a force, not a mass. Now let's assume that this means the thrust is equivalent to the weight force of this ...
Peter Kämpf's user avatar
5 votes
Accepted

How are wind tunnels used with scale models?

During development, a lot of different wind tunnels are used. Scales range from full scale to less than 1/100, and sometimes not only the geometric, but also the dynamic and elastic properties of the ...
Peter Kämpf's user avatar
5 votes

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

There are some things about this wind tunnel that are not as good as the best wind tunnel experiments for actual aircraft. Obvious concerns are that the wing is very close to the bottom of the wind ...
David K's user avatar
  • 1,306
5 votes

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

The short answer is: because not all of the incoming air can fit under the airfoil, so some of it gets pushed up and above the leading edge. This air could also fit under the airfoil by other means ...
AEhere supports Monica's user avatar
5 votes
Accepted

Does Cd number change at different speeds during wind tunnel testing?

Aerodynamic coefficients like $C_d$ and $C_l$ depend at least on Reynolds number, as visible for example in these plots from this answer: So yes, they depends, among other factors, on speed. Anyway, ...
sophit's user avatar
  • 13.5k
4 votes

Which propeller configuration is the one that generates the least turbulent flow in a wind tunnel?

Pusher props are less common than "puller" props for the following reasons. A "puller" prop spins around in air which has not yet been disturbed by the passage of the airplane through it. This means ...
niels nielsen's user avatar
4 votes

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

The Wright brothers certainly thought so, and with obvious results. I highly, highly recommend McCullough's book if you'd like to learn more: Though such apparatus did not look like much, it was to ...
Peter Schilling's user avatar
4 votes

Does the Reynolds number on a smaller model need to match the one of the original aircraft?

This will depend on what you are testing for and how accurately you want to test. It can be sufficient just to match flow regimes. Such that if the actual aircraft has a turbulent boundary layer then ...
DJ319's user avatar
  • 405
4 votes

Why do wind tunnels not have oval turns?

Some closed wind tunnels do have rounded corners, for instance the inner circuit ("thermal test chamber") of the Jules Verne climatic wind tunnel in Nantes. This plan view is from fig. 1 of &...
Camille Goudeseune's user avatar
4 votes

What weather conditions have been tested with a wind tunnel?

Yes, icing tunnels can run at very cold temperatures and can introduce water vapor in quantities sufficient to represent humidity, clouds, and precipitation. Wind tunnels often control pressure and ...
Rob McDonald's user avatar
  • 13.1k
3 votes

How is windspeed scaled in wind-tunnel tests?

It really depends on what data you need and the conditions you need it for. Let's say you want to test a scale aircraft model in a wind tunnel in order to predict the lift forces on the full-sized ...
cbrian's user avatar
  • 340
3 votes

How are wind tunnels used with scale models?

Usually, for low subsonic cases, Reynolds number is matched, while for transonic and supersonic cases, the Mach number is matched. In case you only want the Reynolds number similarity, you can go for ...
aeroalias's user avatar
  • 100k
3 votes
Accepted

What was the first supersonic wind tunnel?

The world's first supersonic wind tunnel started operating in National Physical Laboratory in Teddington, England in 1922. It basically used a pressure tank upstream, which was used to generate ...
aeroalias's user avatar
  • 100k
3 votes
Accepted

Can a wind tunnel simulate airflow when a vehicle goes around a curve?

Wind tunnel is a tool to interrogate aerodynamics, not to investigate flight dynamics (which relies on aerodynamic results to predict vehicular dynamics). As explained in this answer, the additional ...
JZYL's user avatar
  • 11.1k
3 votes

How can I calculate the TOTAL drag of the ENTIRE airplane?

Drag of the $entire$ airplane is readily available by gliding, or monitoring fuel consumption. Checking fuel consumption is a bit more complicated because what you really need is thrust. in steady ...
Robert DiGiovanni's user avatar
3 votes
Accepted

How can I calculate the TOTAL drag of the ENTIRE airplane?

EDIT Doing the math at a speed of 149kts (as suggested by @RobertDiGiovanni) and a weight halfway between EW and MTOW, gives a total drag of some 308lbs which should be a reasonable value. Try with: ...
sophit's user avatar
  • 13.5k
3 votes

Why does this curved wind tunnel rotate?

An automobile with front steering pivots on its rear wheels. This may cause a significant amount of side lift in front from a change in the relative wind, making it more difficult for the tires to ...
Robert DiGiovanni's user avatar
2 votes
Accepted

How to calculate the drag on an airfoil from momentum equation (Fundamental of Aerodynamics 5th edition, J.D.Anderson)?

You are basically asking two questions here: How do we choose an appropriate control volume? What effects does the physical geometry of a wind tunnel have on our ability to make accurate measurements?...
Peter Schilling's user avatar
2 votes

How to calculate the drag on an airfoil from momentum equation (Fundamental of Aerodynamics 5th edition, J.D.Anderson)?

those are some great questions. I will try to be very concise. Firstly, regarding to the line ‘bh’, there is no fixed length you can calculate. Ideally you want to make sure you get measurements of ...
alv's user avatar
  • 21
2 votes

Lift and Drag Coefficients using load cell data

I guess your design is a conventional one. One approach could be integrating two load cells in between the tail and wing sections. You can measure drag force and moment. And the moment may help you ...
Gürkan Çetin's user avatar

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