two phase stratified flow. convergence problem
 

i am simulating wavy stratified flow (2D, two-phase, steady)using euler-euler and mixture model. it runs completely normal until abt 15 iterations and then the residuals become crazy (2-3 big amplitude oscillations) and it stops with typical errors in this situation like floating point exception:Overflow and stopped in routine c_fpx_handler.

any advice here is appreciated. thanks