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-   -   Tips for meshing my geometry (http://www.cfd-online.com/Forums/ansys-meshing/72688-tips-meshing-my-geometry.html)

Gearb0x February 15, 2010 06:50

Tips for meshing my geometry
 
Hello,

I tried to run a simulation on this geometry :

http://yfrog.com/jtgeometryzj

but I get weird results for the pressure. My professor suggested I could have done wrong things with the mesh.

What I would like to have is a Low-Re mesh (y+ = 1)

To find the position of my first cell near a wall I used these formulas, found on a tutorial on the internet wich explains how the distance from the wall :

y+ = U_tau * y / nu
u_tau = sqrt(Tau_wall/rho)
Cf = Tau_wall/(0.5*rho*U_infinite˛)=0.0244/(Rex^(1/7))

My fluid is air so nu = 1.6*10^(-5), rho = 1.2

Imposing y+ = 1 and calculating, I find y = 2.22*10^(-5)
I used my average Reynolds for Rex (I don't remember exactly what Rex is...) wich is 40 000 to find this result

This is quite small ... I don't know if this value is correct or not

And for the mesh, I don't know if it's better to use the "boundary layer tool" from gambit or not.
Since my professor said the problem could be the mesh, I would like tips to mesh this geometry (if you have a good tutorial, ...)

Thanks for the help


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