Convergence Problem when using the Periodic Flow Condition

Hi everyone,

I'm currently using the Laminar Two Phase Flow- Phase Field(tpf) model in Comsol 4.4. The geometry setup is attached.

The problem is when I applied Periodic Flow Condition to the left and right side, the time-dependent solver cannot converge. The error message is something like "Fail to get consistent initial values. The last time step is not converged". When I replaced the Periodic Condition with Inlet and Outlet, the error disappeared. So I just assume that there was something wrong with the periodic flow condition.

Thank you all for your attention and your help is much appreciated.

Best regards,
Huifeng