Small scale windtunnel building.

[Osxy]

Hi all, as a school project we are trying to build a small scale windtunnel.
I've been doing a lot of reading, the design of the tunnel is basicly done now. But now comes the real math's.
So I got a few questions which i hope that can be answered by one of you guys.

To deside the scale of the tunnel i need to know what the proportion is between the scale of the model and the windspeed. I've read several things and really can't figure out what formula to use.
Aka: If scale 1:24 windspeed 1:?

What is the best method to cancel most of the wind turbulence, I've seen some construtions that make a grid before the fan.

Many thanks in advance from this confused physics student from Holland (Havo5).

 

[mgb_phys]

Look at "reynolds number" for an idea of how flow scales.
I think low speed wind tunnels tend to have the fan downstream of the model and pull the air in from outside to reduce the turbulence.

 

[Osxy]

So we are now some time later. And basicly all the planning is done and the first materials are coming in now.

The windtunnel will be a total over 1m 30cm, with a diameter of 30cm.

Some of our 3D concept pictures:
http://wiki.osxy.nl/images/b/b8/V4-final.jpg"
http://www.viddler.com/osxy/videos/4/"

Measuring will be calculated based on the angle of the tube (grafity) and with windmeters placed in front of the fan and in the end of the tunnel.

Hopefully we will have the tunnel working within the next month.

 

[russ_watters]

Very nice rendering. What kind of fan are you going to use? I did this project when I was in school and used a 1 horsepower (750 watt) model airplane engine/propeller, which produced 90 mph (40m/s) in a test section of roughly the same size. People tend to underestimate the necessary fan speed power (though if you are just testing cars, maybe it doesn't matter as much).