Hi,
I have a problem witch have three type of boundary conditions, pressure inlet, pressure outlet and wall, it is a Convergence-Divergence (C-D) Nozzle.
after start calculate in Fluent, this warning is appear:
turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 549537 cells
I was changed turbulent model, refine mesh and checked boundary condition, but this warning did not disappear.
In addition, after 2000 iteration, suddenly Fluent was stop and exit run without any message. i am so confused about this problem. can anyone help me?
This error message or warning appears, if ANSYS Fluent is already on its way to divergence. The eddy viscosity is at this moment in time already so unphysically high, that the "solution" can no longer be interpreted in any physical terms.
I would suggest, that you give your applied boundary conditions a 2nd thought, whether they are realistic and not contradictory in any sense. Sometimes for converging-diverging nozzles which are leading to transonic or even supersonic flows in the nozzle throat it might be necessary to choose a very careful flow initialization or even to slowly ramp up the boundary conditions from subsonic conditions.
Thomas Frank
Thanks for your answer;
would you guide me, how i can simulate supersonic flow in C-D nozzle? Do you know some references about that topic?
The most prbable problem is the quality of the grid, expecially the y+ value near the wall is too large. the height of the first layer of grid can be calculated by using NASA viscous grid space calculator. if this aspect has been considered, it may be the setting of turbulent flow in the boundary conditions.
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