rhoPimpleFoam vs. rhoCentralFoam
 

Hello,
at the moment i am investigating the differences of pressure-based vs. density-based solvers for subsonic flows. I am testing on the Axisymmetric subsonic Jet from NASA:
https://turbmodels.larc.nasa.gov/jetsubsonic_val.html
This case has a speed of ca. 0.5Ma, so i think a interesting point to investigate between pressure and density based.
I managed to set up the rhoPimpleFoam Case and get decent results. However the rhoCentralFoam is giving me Headaches. I am getting wildly diffrent results and dont quite understand why. I realize that the pressure-based solver should probably perform better at such a small Mach-number, but i just don't think it should perform this badly. I attached two screenshots from paraView and both of the cases, without the time folders and mesh because of size reasons. Maybe someone is interested in this and could take a look.


Cheers !

rhoCentralFoam is typically very dissipative. I have experience with it in LES calculations for Mach 2 jet and I find sonicFoam to be more accurate at the same mesh resolution, albeit it requires a lot of inner and outer correctors leading to higher computational cost. You must try rhoCentralFoam with different interpolation schemes (vanLeer or Gamma), different divSchemes for turbulence quantities (other than upwind), and try running it without a turbulence model with laminar setting to see if there is any change. But I would suggest refine your mesh further and see if you see any improvements in rhoCentralFoam results as eventually it may just be a question of dissipation. You can also try the rhoEnergyFoam solver that was developed independently (I'm sure you can find the source code with a google search and compile it if you have installed OF with source code).