2nd order and Turbulent-viscosity ratio error
I am working on a combustor, and for the moment I simply try to model the airflow inside of it.
I designed 1/6th of it to use its periodicity.
I have generated several grids with various geometries of the devices, and for some reason, I always get a "Turbulent viscosity ratio has been limited" error on some of them when I switch from a 1st order converged solution, to a 2nd order (Presto for the Pressure, 2nd order for the other variables).
The problem always comes from the inlet of my device (I have specified a mass-flow inlet).
Here is a picture of the turbulent viscosity ratio of the inlet, for a converged 1st order :
and after a few iterations with the 2nd order :
I don't know how to get rid of these viscosity bubbles.
I tried to set some yplus modification, but I am not sure I am doing it correctly, and it doesn't have any effect.
Here is the detail of my simulation :
Green-gauss cell based implicit steady solver
k-e standard model for the viscosity, with non-equilibrium wall function.
I set the air as an ideal gas.
The BOCO of the outlet is a negative pressure-outlet.
What should I do to have a correct viscosity near my wall ? (I tried to adapt the model with a normal distance from the boundary, to refine the grid near the wall, but the error keeps appearing a few iterations after).
I suggest you keep on iterating. The problem should dissipate. I expect your "bubbles" are caused by a sudden temperature change due to combustion. You can check if in the locations of high viscosity you have combustion taking place.
Thanks for your fast reply.
The problem is that at the moment, I am only modelling the airflow, with no fuel added and no combustion.
I tried to keep on iterating, but these area usually spread and make the simulation crash :/
in that case go to
solution - monitor - limits
(the path might not be exact)
and change the viscosity limit.
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