SimScale CAE Forum

Nozzle Compressible Flow

Hello to everyone!

I am working in a compressible flow through a nozzle and I am having a lot of issues. First, I had the problem explained in this Topic but after ramping the pressure I started having results. The problem is that the results are not physically possible (negative pressure, high velocities, etc). All of this was a Steady-State simulation.

Then, I read in a forum that rhoSimpleFoam does not deal well with shock waves, etc. So I created a Transient simulation and, now, I do not have negative pressure values, but the results are not good (the flow behaves as subsonic when it should be supersonic, at least analyticaly). So I thought that trying to improve the residuals (that didn’t look very good) would help. I started messing with the numerics as I have readed in different Topics, but nothing.

If someone have any idea, please, that would be awesome.

Here is my project:
https://www.simscale.com/projects/Sguares/nozzle_compressible_flow_3/

Here there are two simulations (steady-state and tranient), and a lot of Runs changing BC’s, numerics, etc. Sorry about the mess.

Thank you!

Santi
Pd: the mesh looks fine i think.

Hi Santi!

Tagging @Get_Barried here who also worked on some compressible sims in the past. I might have a look at the setup at a later point. @CFD-SQUAD, feel free to add your two cents here.

Best,

Jousef

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Hi @Sguares,

What is the mach number you are looking at? I assume that you are trying to replicate shock waves internally. This may be an issue. While it is true that rhoSimpleFoam does not deal well with shocks at all, neither does rhoPimpleFoam.

Back when I used to handle shock simulations, the only viable solver that is able to replicate shocks was the rhoCentralFoam. That solver is however disabled now on Simscale. Have you looked through whether rhoPimpleFoam is able to handle shocks yet? I have been out of the loop for awhile, maybe someone has found a workaround.

Do let me know.

Cheers.

Regards,
Barry

1 Like