Compressible pipe flow

[Emil]

Hello,

I'm new to code saturne and I'm trying to realize a simple pipe flow with the compressible model, but could not finish it, because of the following error:

job aborted:

[ranks] message

[0] application aborted

aborting MPI_COMM_WORLD (comm=0x44000000), error 1, comm rank 0

Therefore I set an imposed inlet with a predefined velocity, pressure, temperature and a subsonic outlet with a predefined pressure as well. I tried many different settings, but never could really run a calculation. I received an error message saying that my pressure has diverged after 1 cycle.
My Problem is a straight pipe with a diameter of 5cm.

The reason why I'm calculating with the compressible model is that I need to predefine a pressure at the inlet and the outlet for another problem, which is meant to be calculated with code saturne in a future. If there are other possibilities than to do it with the compressible model, I also appreciate some hints towards those directions.

My listing and error message as well as my case are attached. I am using version 4.0.

I would be grateful for any help!

Emil

[Yvan Fournier]

Hello,

The pressure solver seems to diverge, so your boundary conditions or initialzation are probably too "steep". Did you run the same mesh for an incompressible computation first ? This might help adjust the time step and other boundary conditions ?

I'll remind Erwan, who knows the compressible model best, to check the forum.

Otherwise, could you also post your mesh ?

Regards,

Yvan

[Emil]

Hello Yvan,

thanks for your reply!

I was not able to test your tips yet, because I'm at the office on Tuesday again, but I will keep you informed about it.

But your answer arouses still the same question as in my first post. If I'm not using the compressible model to compute my problem, how can I solve the pressure issue? I have only initial values for the pressure, which were measured. With these values I want to calculate my velocity.

If nothing works out, I will post my mesh on Tuesday as well.

Thanks again for any help!

Regards,

Emil

[Yvan Fournier]

Hello,

My suggestion with a prescribed velocity assumed you had some idea of a expected, or realistic velocity from which you could start, then iterate.

Otherwise, I'll remind Erwan to check these posts. He knows the different compressible BC types much better than I do...

Regards,

Yvan

[Erwan Le Coupanec]

Hello,

Did you try using another inlet boundary condtions (at Ptot and Htot for example, "reservoir" B.C.).
An imposed inlet boundary conditions corresponds physically to a supersonic inlet.

Maybe your case is too constrained because of that. Also as Yvan said, your init. is quite steep (zero velocity everywhere). And you might need some computational time before the waves, created by your inlet conditions (100m/s) meeting your init., are damped.

Regards,
Erwan.