Help!! : AMG ERROR
 

I am trying to simulate a period-inlet-velocity flow (3d, segregated, lam, unsteady)in a tube. What I am using is a compiled UDF which defines the inlet velocity profile.

When I iterate it, an error comes out: Error: divergence detected in AMG solver: x-momentum Error Object: ()

I have adjusted the URF, but it seems to make no contribution, :(

Any one could help me out~~~~~~, THanks a lot