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 paudelrahul January 2, 2013 20:53

Convergence problem

Hello all,

I am trying to do simulation on a valve using steady state pressure based solver. I generated the mesh in Gambit and is structured with 270k cells. The CS area of the inlet is in the order of 1 mm^2. My velocity is 1m/s and the viscosity is 1E-3 for water. while doing the forward flow, it converges, however, the reverse flow doesn't converge. The continuity is in the order of 10^-4, along with the x,y and z velocity. The energy is in the order of 10^-16. And the flow is for Reynolds < 2000. The one I am doing right now is for Re=1000. So, it should be laminar flow.
I need to get the pressure in the inlet and outlet for the reverse flow and I am using area weighted average pressure. However even after 1000 iterations, the pressure at the inlet and outlet keeps changing. I don't know, what value I should take for the inlet and outlet surfaces?

Can anybody tell me how to get it to converge?
I tried using 0.3 for Pressure and 0.7 for momentum Under-Relaxation factors, as well as 0.7 for Pressure and 0.3 for Momentum, under - Relaxation factors.

Sincerely,
Rahul Paudel