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-   -   Surface y+ manual calculation (http://www.cfd-online.com/Forums/main/93303-surface-y-manual-calculation.html)

Yur October 11, 2011 08:56

Surface y+ problem
 
Hi guys,

I need toget the surface y+ results for internal flow. I have the following equation now, but it's not showing me the correct values. Could somebody give me a solution for this.

surface_yplus = (y_velocity*cell_size)/char_viscosity;

The y_velocity is the downstream velocity direction. The cell_size is different for each region in the geometry and the char_viscosity is just a constant.

ps. It's a low speed simulation (0.75 m/s)

Thanks in advance.

bluebase October 23, 2011 12:53

Hi Yur,

may be it's late:

Check your formula again and compare with http://www.cfd-online.com/Wiki/Dimen...e_%28y_plus%29

u_star is not the downstream velocity.

When you follow the link for friction velocity one gets:
u_star = sqrt( tau_w / rho )

Follow the link for wall shear stress to get a formula to compute tau_w.

I hope this is helpful.

Sebastian.


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