Forced convection vs isothermal

jeffberg

Hi:

I have a question regarding the cfx solver and I'm hoping someone can give me an answer

When I run a simulation in CFX with isothermal flow of air, I get a converged solutiuon. When I add a uniform heat flux to one of the wall boundary conditions but do not invoke buoyancy and use the results from the isothermal case as initial values, the momentum residuals change. I dont understand this as there is nothing in the momentum equations that should invoke a change in velocity. Does the CFX solver do something that I'm not aware of. Does anyone know the answer to this?

Jeff Berg