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-   -   High turbulent viscosity, problem with BC (http://www.cfd-online.com/Forums/fluent/44544-high-turbulent-viscosity-problem-bc.html)

Narmin April 27, 2007 08:56

High turbulent viscosity, problem with BC
 
I am simulating a case in which I do not have the boundary conditions at inlet and outlet. Instead, I have pressure data at some cross section within the domain. I know the mass flow so I can specify a mass flow inlet and a pressure outlet. I do not know the outlet exact pressure but I assume some close value and I am going to correct it according to the value, I get for different cross section. The problem in my simulation is that I get warning about high turbulent viscosity in many cells while the residuals seem to decreas all the time. Could anyone help me to identify what is the reason for high turbulent viscosity.

Thanks, Narmin

Thomas May 2, 2007 09:41

Re: High turbulent viscosity, problem with BC
 
Could be lot of reasons: First of all: have u scaled up correctly your problem? Where are located the regions of high turbulent viscosity? If they're close to inlets or outlets try to decrease the turbulent length scale or the percentage of velocity used to calculate the turbulent kinetic energy. If the'yre in regions where high velocity gradients exist, you have to refine your grid in those regions. Try and let us know.

thomas

Narmin May 8, 2007 03:17

Re: High turbulent viscosity, problem with BC
 
Hi,

I could not visualize, where the high turbulence intensity cells are situated, the number of my cells are too high, 13.5 m and even when I want to adapt the high turbulence intensity regions the process stops but I will try to make finer meshes at the enterance where I have quite coarse cells. thanks for your help.


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