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-   -   Transonic jet simulation (http://www.cfd-online.com/Forums/openfoam-solving/60169-transonic-jet-simulation.html)

magnus January 24, 2006 14:40

Hi everybody, I am a beginn
 
Hi everybody,

I am a beginner OpenFOAM user with a wish of doing an investigation of the acoustics generated by a transonic jet through a nozzle. For this I tried rhoSonicFoam with initial conditions for the velocity field given by an incompressible solution of the same case.
I then start the compressible case using a really low Courant number. After some 6000 iterations the calculation still looks good but then blows up very quickly.
This is the case both when i use higher order vanLeer but also when I tried the upwind scheme.

As I am a beginner user maybe this is not the right solver that I have choosen.
Does anybody have ideas/suggestions of what I can do?

Thanks for your kind answers!
/Magnus

mattijs January 25, 2006 04:20

It is usually something physic
 
It is usually something physical happening that causes this blowing up after such a long time of stable running. Check the solution just before it blows up. Maybe there is something happening (inflow?) at the outlet? Is the initial shock (from starting from an incompatible solution) reaching the outlet. Or is the solution finally going supersonic?

sshyu January 25, 2006 04:38

IC and BC should always be an
 
IC and BC should always be an issue. A bad IC might eventially kills your calculation. But sometimes, the code might get survived and give you final solution. This would depend on the physical problem. As for BC, it would either give you a wrong solution, or just blow up. In my experience, the FDM tends to survive for quite a long period of time before it blows up, or gives you wrong solution. As for the spectral-like method, it would diverge quite quickly. This is a good thing though.

magnus January 25, 2006 11:17

Many Thanks for your input!
 
Many Thanks for your input!

I restarted my calculations, using first order schemes, with zero for pressure and velocity in the interior. I can see that the problem comes from the inlet patch
I looked throught my boundary conditions and I found that maybe I misunderstand the meaning of pressureInletVelocity. What is the value i need to specify there?

I want to specify totalpressure and totaltemperature what is the correct velocity BC for this setup?

/Magnus

magnus January 25, 2006 11:19

Many Thanks for your input!
 
Many Thanks for your input!

I restarted my calculations, using first order schemes, with zero for pressure and velocity in the interior. I can see that the problem comes from the inlet patch
I looked throught my boundary conditions and I found that maybe I misunderstand the meaning of pressureInletVelocity. What is the value i need to specify there?

I want to specify totalpressure and totaltemperature what is the correct velocity BC for this setup?

/Magnus

magnus February 1, 2006 12:54

Hi, I realize that what i w
 
Hi,

I realize that what i wanted to do is not implemented.
So I ask instead if somebody can give me a suggestion of which solver to use for a transonic turbulent jet with moving shocks. The inlet is subsonic and I whish to use LES for closure.

Thank you
/Magnus

eugene February 1, 2006 13:23

coodles with "transonic true
 
coodles with
"transonic true;"
added to the PISO subdictionary.
No way it will capture shocks properly though.

thauser February 11, 2006 15:57

Could I modify sonicFoam (merg
 
Could I modify sonicFoam (merge with coodles) to create a LES solver for compressible flow with shocks? Or are there better ways?

tangd June 14, 2006 02:43

I have the same question as wh
 
I have the same question as what Magnus asked:
"I want to specify totalpressure and totaltemperature what is the correct velocity BC for this setup?"
I also use coodles, hope somebody can give me the answer, thanks!


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