Transitional SST Trouble
 

Hello all!

I am trying to simulate the results by You et al.'s paper, 2002 (Direct numerical simulation of heated vertical air flows in fully developed turbulent mixed convection) of air flowing up a uniformly heated vertical pipe in Fluent.

I have been advised to use the Transitional SST turbulence model, but it is struggling to converge. Has anyone got any idea what I might be doing wrong or what I could do to help it?

The pipe has dimensions; D=0.05m, L=5m. Ux=0.55m/s. I have modelled it as 2D, steady and axisymmetric, and am using a pressure based solver. I have tried both constant and piecewise linear varying properties of air with similar results. The SIMPLE scheme is used and all others are second order upwind. The pipe has a uniform heat flux on the wall. Inlet BC are velocity based, and outlet is outflow

I have read that others have experienced problems due to the presence of gravity, yet the solution still won't converge for no gravity applied at all!

Have been trying to rectify this problem for quite some time and am getting increasingly frustrated! Any and all help would be gratefully received!

Thanks