Single phase flow with heat transfer in vertical tube

Hi,

Actually, i am trying to model two phase flow in vertical tube.
So, as I am new in COMSOL, i AM STARTING WITH SINGLE PHASE FLOW WITH HEAT TRANSFER IN VERTICAL TUBE. for LAMINAR FLOW my MODEL IS GETTING CONVERGED. But, when I am trying with turbulent flow.

It is giving error with the following words:-


Failed to find a solution.
Out of memory during LU factorization.
Returned solution is not converged.


Please respond


AMIS SHANKAR