[yayale]

I am simulating airflow inside a tube. The flow is a sinusoidal flow, flow rate starts negative and ends as positive flow rate. (periodic flow).
The problem is that at reversal, the solution is diverging.
What solutions are there for such flows ?
I tried adaptive time step, and tried decreasing time step, both did not work.
Boundary conditions:
Pressure outlet at one end (zero gauge pressure).
Mass flow inlet at the other end (sinusoidal).
Attaching residuals and mass flow rate plots. Instabilities are clear at flow reversal regions.