Flow test in a wind tunnel

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Chen Chen
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Flow test in a wind tunnel

We would like to test air flow pattern in a wind tunnel. The wind tunnel is made by plastic, and we tried to reduce the surface reflection by putting black aluminum plate on the bottom and back wall. These are two images we took, the signal to noise ratio is very low. Do you have idea where is the problem? Too much smoke, reflection, laser power (it is max now)... Thanks for your help!
Frame 1
Frame 2
William William
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Re: Flow test in a wind tunnel

Hi, this really looks like a bad s2n ratio. I don't know what camera you are using, but it looks like the gain is way too high.
You can try to
-use a longer exposure time and smaller gain
-use a different lens with better f-number
-use more laser power or a pulsed laser
-make the opening angle of the light sheet smaller and move the camera closer to the sheet, so you have more power per area.
-Use a more light sensitive camera
-Use a different wavelength or remove any wavelength filters from the lens

There are many more possibilities that depend on your actual situation. But doing PIV with your current setup will be difficult.

Please consider donating for the PIVlab project:
http://paypal.me/pools/c/81Y8wBVi4y

The developer needs to update to a recent Matlab release in order to keep the project running.

Chen Chen
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Re: Flow test in a wind tunnel

Thank you for your reply. I will try your suggestions to see whether we can reduce the noise level. We have used this PIV system for some other tests, it went well. I am curious how to design a wind tunnel test to eliminate the reflection and reduce the noise. For example what type of material for wind tunnel (we use plastic)?