problem: very high turbulent viscosity ratio

November 8, 2005, 11:28

Dear FLUENT-expert,

I do an open channel simulation (VOF) downstream a water power plant. The calculated velocity field seems sensible. There is a problem with the turbulent viscosity ratio (TVR) however.

It is very high and is limited by FLUENT automatically to 100.000 in approx. 1.500 out of approx. 100.000 cells. I've read in the user's guide that the TVR should be < 10 in external flows. My results are far from this.

Any ideas why this is so and how to reduce TVR?

Thank you!

Christine

November 8, 2005, 13:10

Make sure your turbulent initialization is not k=1 and epsilon=1 but something more sensible.

November 9, 2005, 08:23

Hello Christine.

Sometimes this limitation occurs due to bad mesh geometry. So maybe refining/coarsing the mesh will help.

Regards Martin

November 8, 2005, 11:28	problem: very high turbulent viscosity ratio	#1
Christine Sindelar Guest Posts: n/a	Dear FLUENT-expert, I do an open channel simulation (VOF) downstream a water power plant. The calculated velocity field seems sensible. There is a problem with the turbulent viscosity ratio (TVR) however. It is very high and is limited by FLUENT automatically to 100.000 in approx. 1.500 out of approx. 100.000 cells. I've read in the user's guide that the TVR should be < 10 in external flows. My results are far from this. Any ideas why this is so and how to reduce TVR? Thank you! Christine

November 8, 2005, 13:10	Re: problem: very high turbulent viscosity ratio	#2
Ernest Bertrand Guest Posts: n/a	Make sure your turbulent initialization is not k=1 and epsilon=1 but something more sensible.

November 9, 2005, 08:23	Re: problem: very high turbulent viscosity ratio	#3
Martin Guest Posts: n/a	Hello Christine. Sometimes this limitation occurs due to bad mesh geometry. So maybe refining/coarsing the mesh will help. Regards Martin

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