Dear Friend,

The problem is impeller-baffle problem. It is 3-D problem. The geometry is similar to Fig. 16.2.3 in Fluent Manual. The interface is the dash line in the Fig. 16.3.1. MRF method is used here. The flow is rotationally periodic.

If I use periodic boundary condition on the top and bottom boundary, I can calculate the flow field. But if I change the top boundary into velocity inlet boundary and the bottom boundary into outlet pressure boundary, I cannot calculate the flow field. When I interate, the first interation cost a very long time and it cannot be finished. During the calculation, there is no error message coming out.

Then I change one of the top boundaries (two fluid zones) into periodic condition again and the other keeps the inlet velocity boundary. On the same time, I change the corrponding bottom boundary into periodic condition and the other keeps the outlet pressure boundary. The interation is working. Could you tell me what I can do to solve this problem ?

With best regards, You

Try the following:

- reduce the axial extents of the MRF zone, i.e., move the top and bottom of the MRF interface closer to the impellers and away from the inlet and outlet

- set your velocity inlet and pressure outlet BCs

- solve in relative frame of reference (or absolute depending on your convergence behaviour). Define->Solve->Solver...

- follow the guidelines in Section 16.2.6 for solving rotating reference frame problems.