code_saturne User's Forum

Hi,

I try to simulate a flow of a compressible fluid (ideal gas) through a simple pipe (length 0.5 m; diameter: 0.015 m). I use a unsteady algorithm and the compressible model. The xml file with all settings and the mesh med file is attached. I defined a mass flow of 0.2 kg/s, a pressure of 150000 Pa and a Temperature of 293 K at the inlet. When I start the calculation I get this error message in the listing:

@@ WARNING : Error during execution,
@ =========
@ Unexpected type of predefined compressible boundary
@ conditions.
@
@ The computation will stop.
@
@ Check the boundary conditions in
@ cs_user_boundary_conditions

The whole day I tried to make the solver running, however it was not possible. Has anybody an idea, what the problem is?
I start the same calculation with water and it works. So it seems that the mesh model is OK.

Emil

Hello,

Indeed, I ran your case, and indeed the compressible BC's error logging need cmore detailed messages and postprocessing...

But basically, you cannot use rough walls with the compressible module, so you need to switch back to smooth walls (most compressible applications we know of have rather smooth walls), or you would need to extend the code to handle rough walls...

You'll also need to initialize 2 physical variables (for example pressure and temperature), which does not seem to be the case in the XML you sent...

Regards,

Yvan

Hi Yvan,

thank you very much for your help. After I have changed the parameter to smooth wall and defined initial values for the pressure the calculation runs!