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Materials to make skin friction negligible

  1. Nov 25, 2015 #1
    Hi,

    I need to run wind tunnel tests on a simple shape which will be made of foam whilst the skin friction is to be negligible. Is there easy ways of cover the model to achieve this ?

    thanks
     
  2. jcsd
  3. Nov 25, 2015 #2
    The best you can do is to make the surface smooth and very even. Spray paint may not work because it often "eats" foam before it drys.
    With some experimentation, you might find some combination of liquids and sprays that will work. Like a primer followed by a glossy coat. Or maybe a glue followed by a glossy. It will depend a lot on what foam you are using.
     
  4. Nov 25, 2015 #3

    cjl

    User Avatar

    Are you trying to measure the drag, or are you trying to measure lift? If you're trying to measure drag, it will be very difficult, and your best bet will be to try to get the reynolds number up as high as possible and make the surface as smooth as possible. If you're measuring lift however, it'll be a lot easier to ensure that skin friction isn't substantially affecting your results, though the procedure is the same (smooth surface, high Re). If you want to confirm that skin friction is small, run tests over a wide range of reynolds numbers and look at how your nondimensional coefficients are affected by changing Re. If your skin friction is having a negligible result on the aerodynamics, the nondimensional coefficients will not vary very much with Re.
     
  5. Jan 11, 2016 #4
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