problem in simulation exhaust fan...
 

Dear all,
I have problem with simulation exhaust fan. My setting is MRF model, RNG k-eps, RNG option: Swirl dominated flow, and wall treatment: enhanced wall treat ment , 500 RPM, second order for all dicretization scheme and default.
I have found convergence problem in continuity. I have tried to change momentum under-relaxation factor from 0.7 (default) to 0.5. But it's no use. What i should do??
Thank you for your help.
THA