2D compressible viscous flow through nozzle with sonicFoam
 

Hi,

I am trying to simulate high-pressure gas (up to 10^7 Pa) being forced through a very narrow ( < mm) cylindrical 'nozzle' into a vacuum. I am using sonicFoam as a transient solver to look for instabilities etc in the flow.

However, as the flow reaches the narrow 'nozzle', much of it reflects and a high-temperature, high-pressure stagnant region grows behind the nozzle, eventually crashing the code when it reaches the edge of the simulation box.
This is obviously a challenging situation to simulate, so I wonder whether anyone would have some tips on how best to go about this?

I've attached my case files

Thanks for your time