Hi, I'm running an airfoil simulation in Fluent for low reynolds number.I'm using the k omega sst model for transition purposes. My residuals for k and continuity does not go below e-02 and it oscillates around that range. How do i make my solution converge? I have no problems with this when running high reynolds number though. I am using 2nd order upwind.

Rif

Possibly you've got flow oscillations (buffet) due to the instability of separated boundary layers. What freestream Mach number do you prescribe?

I would suggest to do the following. I would create a very very coarse case with same geometry. Will run it with same conditions.(use first order scheme for it). Get some solution. Export the solution to interpolation file. Open the fine grid case, read this file as initial guess. Run first few iterations as first order. Switch to second order.

It should work out.

Are you using limiters ? They can stall convergence.

Are your boundary conditions good ? Are the boundaries sufficiently far from the airfoil ?

Try to plot the residuals and see in which part of the flow domain they are high. That may tell you something more about the reason for stalled convergence.