Reverse flow warning and solution divergence
 

Hello,

I am simulating a steady laminar flow in a geometry very similar to a annular flow (flow between two concentric cylinders). My boundary conditions are velocity inlet and pressure outlet.

As the simulation goes on, Fluent warns about reverse flow in a number of faces on the pressure outlet zone, and the number of faces with this problem increases. The solution converges at firts but eventually begins to diverge as seen in the figure (around iteration 260).

Actually I don't know what does Fluent mean by reverse flow. When I check the velocity vectors at any point during the simulation, they are all pointed outside of my domain on the pressure outlet zone.

Please help,

Thanks

http://4ax.ir/images/snap20kxk.png