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-   -   Naca airfoil with to much drag (https://www.cfd-online.com/Forums/cfx/22297-naca-airfoil-much-drag.html)

 Andreas March 15, 2006 11:26

Naca airfoil with to much drag

Hi!

I try to calculate a flow around some Naca 4 digit airfoils. In my calculation the lift is nearly right, but the drag is much too high. I'm comparing the calculated values with the book "theory of wing sections". Can you give me a reason or advice? I use a wall as boundary condition for a profil and the calculations are done with the standard k-epsilon turbulence model.

Thank you Andreas

 ms March 15, 2006 11:41

Re: Naca airfoil with to much drag

The K-E is probably your problem. they are not ideally suited for these kind of flows. An SST model would prob give you better results.

 Andreas March 15, 2006 11:53

Re: Naca airfoil with to much drag

Hi!

I tried this too, because I had the same idea but the results are nearly equal. So I don't know what I'm doing wrong.

Andreas

 Ogbeni March 15, 2006 13:22

Re: Naca airfoil with to much drag

What advection scheme are you using ? Try specified Blend or High Res.

 vijesh joshi March 15, 2006 13:43

Re: Naca airfoil with to much drag

what scheme you are using? because if you are trying for some supersonic / hypersonic case, then use upwind scheme. other thing is use local time scale factor<1.

 PetrK March 15, 2006 13:52

Re: Naca airfoil with to much drag

Check this forum, there are a lot of topics with this problem. You need very fine mesh, y+ bellow 2, run as transident, SST turbulence model with transition model, high resolution advection scheme.

 AndiMb March 17, 2006 07:13

Re: Naca airfoil with to much drag

Hi!

Thanks for your help. It worked. Sorry, that I didn't search in the post.

Andreas

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