We are doing simulations of turbulent flows in stirred tanks equipped with 6-blade radial turbine and using Sliding mech technique (mixsim and Fluent 4.5). We have a problem of convergence of pressure term. We have tried to increase the number of sweeps (more than 100), change the underrelaxation parameters, we have also tested different time steps. However the problem remains. May be someone can help. Many thanks and best regards. Mounir

It often occurs that you encounter poor convergence of the continuity equation when modeling stirred tanks with the sliding mesh capability. The possible culprits are poor grid quality and too large a time step (and possibly a high rotational speed). Reducing the under-relazxation factors by 50% or more is usually necessary. For the time step, start off with auto-time step adjustment setting the grid increment to 1. Consider solving the problem first using the MRF model (see page 13-21 of the Fluent 4 Users Guide).

I hope this helps.