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- - **Sonic foam solver for a subsonic problem**
(*https://www.cfd-online.com/Forums/openfoam-solving/59734-sonic-foam-solver-subsonic-problem.html*)

Hello all,
I want to solve Hello all,
I want to solve a non isotherm compressible problem in a gas flow context. For that, I use the sonic foam solver. In my problem, the velocities are subsonic and in this case, the computations do not converge. How can the numerical parameters be changed to have a converged solution ? Thank you Stephane |

Henry...Hi
Henry,I have seen some comment where you claimed to have got good results for subsonic cases. Could you please tell which one you have used? I am currently working on sonicFoam solver to run a low mach flow (10m/s and 1m/s). but unfortunately none of the case is running quite well for forward step problem. The solution obtained is unrealistic to be honest.The solver seems to be working well for supersonic foam though. In the sonicfoam solver code, i can see a line at the top of the loop: #include "rhoEqn.h" which solves the eqn: fvm::ddt(rho) + fvc::div(phi) i am wondering what this equation is doing here, when PISO is a pressure based eqaution and it does not solve for density in continuity equation. ??? Also the PISO proposed by Issa is taking out the central part AU0 from H(ui), but your code doesnt seems to be taking that in account. however the code seems to be stable but the final result is poor for compressible flow in low mach region of 0.03. (and worst in further low) I am looking forward to your suggestions and planning to work on the solver to run for low mach flow in the region of 0.001 or lower. regards, Nishant |

Hey!! Did you find a way to make sonicFoam work for subsonic cases? I used rhoSimpleFoam and the simulations seem to work fine (they agree with experimental data), and now I´m trying to validate them with sonicFoam, but the residuals diverge :( I´m wondering if it´s because sonicFoam is meant to be used only with supersonic flows, but I have seen papers where it has been used for subsonic cases, so I´m not so sure.
Thank you in advance!! Andrea |

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