Re: [ff3d-users] Navier-Stokes problem

[Thomas B]

Hello,

thank you very much for your help.

Unfortunately the results are not quite the one I expect: F_z should at 
least be positive (a tilted plate in a flow should be experience a force 
upwards).

Is anything basically wrong to simulate such a case?

Regards,
Thomas

Stephane Del Pino wrote:
> Hello Tomas.
>
> I noticed something wrong in your ff3d file:
>
>         double eps = 1000;
>         function P  = eps*one(<1,0,0>)+1
> // ... then ...
>          double fx = int[M](ki/eps*u);
>          double fy = int[M](ki/eps*v);
>          double fz = int[M](ki/eps*w);
>
> The problem is that in my mind, eps is something small and P is defined using 
> 1/eps so the force here is not evaluated correctly. I suggest:
>
>         double eps = 1E-4;
>         function P  = 1/eps*one(<1,0,0>)+1
> // ... then keep ...
>          double fx = int[M](ki/eps*u);
>          double fy = int[M](ki/eps*v);
>          double fz = int[M](ki/eps*w);
>
> I have run you example for a few iterations, and I get for instance
> <#i=8
> <#Fx=-0.378171
> <#Fy=2.7602e-05
> <#Fz=-0.0644279
>
> Is it more what you expect?
>
> Best regards,
> Stéphane.
>
>
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