convergence issues in cojugate heat transfer problem

Hi,

I am trying to solve a conjugate fluid flow and heat transfer problem. The problem has a channel with fluid flowing through it and surrounding media which has some heat sources.
I am having issues when I increase the inlet velocity. Everything is laminar as it is a microchannel. As the inlet velocity is increased the solution fails to convergence.
I have tried including the results from lower velocity as initial condition for higher velocity but that is still not helping in convergence.

Any suggestion will be highly appreciated.


Regards,
Sumeet