Hi there,

I have written a code based on SIMPLER method for the flow in a duct. I have expanded my code to variable density (I added term d rho/dt in the continuity equation). The issue is when I use fixed time step the code works fine, when I use variable time step if I reduce the time step say by 10 times less then I have a small jump in my pressure, this jump goes away in the next time steps. Am I doing something wrong? Or is it the nature of SIMPLER algorithm that is so sensitive and stiff. I would like to know your feed back. My understanding is that the SIMPLER is very sensitive to term (d rho/ dt). Your help is appreciated.

Erik,

Not specific answer to your query, but the following paper might be helpful:

K.C. Karki and S.V. Patankar, Pressure Based Calculation Procedure for Viscous Flows at All Speeds in Arbitrary Configurations, AIAA J V27 N9, 1989, pp 1167-1174.

Rami