Simcenter STAR-CCM+ What is meant by "Turbulent viscosity limited warning" in the output window
2023-11-02T04:39:07.000-0400
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Summary
The “Turbulent viscosity limited warning” occurs when the ratio of turbulent to laminar viscosity exceeds the Maximum Ratio.
Details
The Turbulent viscosity limited warning occurs when the ratio of turbulent to laminar viscosity exceeds the Maximum Ratio.
There are two occasions when you are likely to encounter repeated warnings saying that the turbulent viscosity is being limited in some cells.
Generally one would only increase the Maximum Ratio if the simulation has a high Reynolds number and no errors seem to be present in the simulation setup. The turbulent| viscosity ratio is proportional to a turbulent Reynolds number, where the velocity scale is typically given as k^0.5 and the length scale as (k^1.5)/epsilon (for a model that is based on the eddy viscosity concept). If you expect high turbulent Reynolds numbers (which occur when the mean flow Reynolds number is high), you could try increasing the Maximum Ratio limit by one or two orders of magnitude.
If you do not expect high turbulent Reynolds numbers, it is likely that another problem is present in your simulation, such as an incorrect boundary condition, or a mesh that has not been scaled correctly.
See also:
Troubleshooting RANS Solvers.
How to display Turbulence Intensity as a scalar value
What turbulence model should be used for my simulation?
Simulating Physics > Turbulence > Reynolds-Averaged Navier-Stokes (RANS) Turbulence Models > K-Epsilon Turbulence > K-Epsilon Solvers Reference
There are two occasions when you are likely to encounter repeated warnings saying that the turbulent viscosity is being limited in some cells.
- During the first few iterations. In this case, it is acceptable due to startup transients.
- Occurring as the flow solution nears convergence. If the flow field yields a reasonable solution, you can modify the limit to remove the warnings.
The Maximum Ratio property is set in the k-epsilon Turbulent Viscosity solver node.
Generally one would only increase the Maximum Ratio if the simulation has a high Reynolds number and no errors seem to be present in the simulation setup. The turbulent| viscosity ratio is proportional to a turbulent Reynolds number, where the velocity scale is typically given as k^0.5 and the length scale as (k^1.5)/epsilon (for a model that is based on the eddy viscosity concept). If you expect high turbulent Reynolds numbers (which occur when the mean flow Reynolds number is high), you could try increasing the Maximum Ratio limit by one or two orders of magnitude.
If you do not expect high turbulent Reynolds numbers, it is likely that another problem is present in your simulation, such as an incorrect boundary condition, or a mesh that has not been scaled correctly.
See also:
Troubleshooting RANS Solvers.
How to display Turbulence Intensity as a scalar value
What turbulence model should be used for my simulation?
Simulating Physics > Turbulence > Reynolds-Averaged Navier-Stokes (RANS) Turbulence Models > K-Epsilon Turbulence > K-Epsilon Solvers Reference