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Old   January 18, 2007, 07:56
Default Problems considering boundary conditions
Morten Andersen
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Hallo all

I have a problem considering the boundary conditions in CFX. I have made an emty wind tunnel with inlet at all the boundaries. I have specified a velocityprofile as shown below

U=alfa*(y/delta)^0.28 alfa=2.99m/s delta=2m

I have used a standard k-epsilon model and specified the turbulent kinetic energy and the turbulence dissipation rate as shown below

k=Uf^2/sqrt(Cmy) with Uf=0.6m/s Cmy=0.09

epsilon=Uf^3/(karman*y) karman=0.41

After the simulation the values of U,k and epsilon at the top and the bottom of the wind tunnel are not equal to the values defined in the boundary conditions before the simulation?

How does CFX uses the defined values at the boundary?

Regards Morten
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Old   January 18, 2007, 10:04
Default Re: Problems considering boundary conditions
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Dear Morten,

You said all boundaries are inlets.. You mean no walls no outlets. What is the fluid doing? It cannot be compressed because there are no walls. It cannot get out because there are not outlets..I am sorry, but I did not understand the setup.

In any case, are you looking at conservative or hybrid values?


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