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-   -   turbulent viscosity ratio on a large duct (http://www.cfd-online.com/Forums/fluent/47514-turbulent-viscosity-ratio-large-duct.html)

newbie March 5, 2008 01:23

turbulent viscosity ratio on a large duct
 
I searched the forum but I couldn't quite get the answer to my problem.

I ran a simulation where water flows through a very large square duct (5x5x30m).

solver: k epsilon standard Inlet: velocity inlet 1 m/s duct wall: smooth wall outlet: outflow

Mesh: quad mesh with 0.3 size (resulting in about 50,000 nodes). gravity on. specified operating density=0

The problem gets the turbulent viscosity limit error (1e5). Strange thing is that when I plotted viscosity ratio, almost all of the water body not close to wall had viscosity ratio around 1e5. How could this be so high in such a simple flow? Is this normal?


Robert March 5, 2008 03:36

Re: turbulent viscosity ratio on a large duct
 
Hi, I think, the FLUENT wrote the following (because this is usually): "Turbulent viscosity RATIO limited to 1e5 in ... cells". You can not (as I know) plot the ratio, only the viscosity, which isn't the same.

You can set the limits in the Solve/Controls/Limits.

Bye

newbie March 5, 2008 13:27

Re: turbulent viscosity ratio on a large duct
 
I really did plot the ratio. To to like pathline or vector or contour, click the turbulance, and than on the below, click the turbulent viscosity ratio.

newbie

shehab March 7, 2008 17:00

Re: turbulent viscosity ratio on a large duct *NM*
 

shehab March 7, 2008 17:05

Re: turbulent viscosity ratio on a large duct
 
may be if you set the specified density to 1000 kg/m^3 this should work. you can't set the specific density to zero. either to deactivate it or to set it as equal to the highest density phase and as you simulate a single phase then you should set it as the density of the water. also what do u mean by smooth wall... is it slipping wall... then try to set it no slip condition. best regards, shehab.....shebos@hotmail.com


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