Q: Simulation convergence with EDM combustion model becomes poorer when switching from k-eps to SST turbulence model. Residuals for mass fractions and temperature oscillate. Temperature damping does not help. What is the reason and how to improve?
A.: In the EDM model the source term is proportional to epsilon. Switching to the SST model, the rate becomes proportional to omega in the near of the wall. Due to turbulence modelling omega can get very high values there. Hence convergence becomes poorer. To avoid this activate the Mixing Rate Limiter under ->Domain->Fluid Models -> Combustion Models->Mixing Rate Limit. The default value is 2500 [s^-1]. This is a good value for gas combustion.
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Q: Simulation convergence with EDM combustion model becomes poorer when switching from k-eps to SST turbulence model. Residuals for mass fractions and temperature oscillate. Temperature damping does not help. What is the reason and how to improve? A.: In the EDM model the source term is proportional to epsilon. Switching to the SST model, the rate becomes proportional to omega in the near of the wall. Due to turbulence modelling omega can get very high values there. Hence convergence becomes poorer. To avoid this activate the Mixing Rate Limiter under ->Domain->Fluid Models -> Combustion Models->Mixing Rate Limit. The default value is 2500 [s^-1]. This is a good value for gas combustion. |
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