SimScale CAE Forum

Help for setting up an external supersonic simulation

Hi all

I’m going to set up an external supersonic simulation soon, and I am not sure where to start.
The simulation is on a ramjet engine. It must simulate the engine being put in a wind tunnel where the airspeed is 350m/s, and the atmospheric pressure is the same than at sea level.

How should I go about setting up the boundary conditions for this?
Should there be a velocity inlet in front of the engine and a pressure outlet behind it? I tried this and got strange results.
My preliminary investigation can be accessed through this link:

https://www.simscale.com/workbench/?pid=506145016763801685&mi=spec%3A3ea58d0e-57cb-4293-a23d-2a828dcc0f28%2Cservice%3ASIMULATION%2Cstrategy%3A1.

If anyone here has experience on setting up a supersonic flow simulation, it is most welcome.

Best regards

Charles

Hi Charles - great project and certainly something for our Community Challenge :wink:

So from an intuitive point of view I would not model this whole component with a windtunnel like domain but rather “close” the ramjet at the end with a surface and also close the other end with a surface to use these as the pressure inlet/velocity inlet and pressure outlet/velocity outlet respectively. However phenomena like back pressure might occur in this case so we would have to do more research on that and you maybe know more on this than I do. Good resource for that: Effect of back pressure and freestream dynamic pressure on a typical Ramjet engine duct under realistic supersonic inlet conditions.

Once the geometry has been optimized that way we can make use of rotational symmetries in the system and model only the upper half of the model as the shock waves will distribute symmetrically along the ramjet. Let me know if that makes sense to you and if you have any data for this case or any validation case that you work with that can be used here.

All the best!

Jousef

1 Like