[Alpha_Ashwin007]

Hi, I'm trying to simulate supersonic flow (M=1.6) through a duct with shocks, first in steady state, then as a transient simulation by varying outlet pressure.
I was able to get a good and stable steady-state solution only after using high-speed numerics. After that, I tried to run a transient simulation and used an udf to vary the outlet pressure sinusoidally. But I'm noticing a bizarre behaviour of residuals.

During each iteration, it is continuously increasing. The timestep I used is 1e-6 (20 inner iterations), which I think is small enough for the frequency of oscillations of the outlet pressure (1000hz).

I am using the density-based solver, second-order discretization, second-order time stepping, high speed numerics, CFL = 0.9, k-w sst model.

I have attached a picture of the residuals and the dp/dt contour which shows some weird distortions, kindly let me know if anyone has any ideas on how to fix this.
Thanks