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turbulent viscosity ratio on a large duct

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Old   March 5, 2008, 01:23
Default turbulent viscosity ratio on a large duct
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newbie
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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?

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Old   March 5, 2008, 03:36
Default Re: turbulent viscosity ratio on a large duct
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Robert
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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
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Old   March 5, 2008, 13:27
Default Re: turbulent viscosity ratio on a large duct
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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
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Old   March 7, 2008, 17:00
Default Re: turbulent viscosity ratio on a large duct *NM*
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shehab
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Old   March 7, 2008, 17:05
Default Re: turbulent viscosity ratio on a large duct
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shehab
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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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