Basic Wind Tunnel questions

  • Thread starter kaiopaka
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  • #1
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So, I am totally not an aerodynamic engineer, but my boss - an organic chemist- thinks we should get a wind tunnel to test some new polymer coatings that our research group developed. In researching and calling around to companies that make wind tunnels, I got a question that i have no idea how to answer - what uniformity of flow do we need? I cannot find anything on how that is quantified, and I'm hesitant to answer "uhh, good". Could I get a little help?
 

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  • #2
boneh3ad
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Well what are you trying to measure in your tunnel?
 
  • #3
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We want to measure any drag reduction that may occur due to these coatings (over standard coatings). Essentially, I think I want to measure the skin friction of a flat plate, coated with the various canditates.
 
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boneh3ad
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Do you by any chance know by what method it is hoped it will reduce drag?
 
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The coatings have very low surface energies, and nano-scale roughness. I was told by my boss that a .1% drag reduction would be considered a success.
 
  • #6
boneh3ad
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Right but the mechanism you are hoping to control determines what your flow quality should be.

I don't know what surface energy even means to be honest, so if you could briefly explain it I may be able to help a little more.

If the nanoscale roughness is what you are hoping will help, that is a complicated problem.

Are you hoping to keep the flow laminar for longer and reduce drag that way?
 
  • #7
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Have you considered renting time in a wind tunnel as opposed to buying your own. Wind tunnels are expensive and you need to know what you are doing to get anything meaningful. And just buying a wind tunnel won't be enough, you need a way to measure the drag and an accurate force balance will be very expensive as well. You also need space for the tunnel, you will probably need pressure transducers and thermocouples, experience in data acquisition and then you will have to invest time in writing software to run everything.

There are plenty of wind tunnels out there where you can rent time and have experienced test engineers run the experiments and get very accurate drag measurements.
 

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