Error about 'Failed to find consistent initial values. Last time step is not converged'

Hi,

I am a new user of COMSOL. I've set up my reactor geometry model and successfully applied the turbulent flow (stationary condition) in my reactor model. However, when I try to simulate my reactor dynamic behavior under time dependent condition of turbulent flow, there is always a problem which says 'Failed to find consistent initial values. Last time step is not converged.'

Besides, when I try to add a turbulent bubbly flow (two phases flow), even under stationary condition, there is a problem about 'the matrix has zero on diagonal'. I don't know how to solve these problems and I will feel very thankful if I can get some advises. Many thanks!

Best wishes,

Dd.