Laminar flow

Hi
I am modelling the flow of liquid alloy during casting process. In the laminar flow physics, I have used inlet boundary condition as velocity field with cast inlet velocity in x-direction, outlet condition as no viscous stress and a volume force calculated by -g_const*rho in y direction. I get an error message on simulation which says 'Failed to find a solution.
Maximum number of Newton iterations reached, Returned solution is not converged'. Can you please help me fix this error?