Forward-facing step give different results in SonicFoam and rhoCentralFoam
 

I tried running the forward-facing step tutorial case using sonicFoam and rhoCentralFoam for endTime = 20s with OF 4.1 on Ubuntu 14.04. At T = 20 the solutions have converged for both solvers. However the answers are different. The results don't agree well with the normal shock values for M = 3. Does anyone have any idea as to why this is so. Please see attached results.

Have you compared this against the literature data? If you look in the original paper for rhoCentralFoam, DOI: 10.1002/fld.2069, you will see some results for this case. Also, to get similar results in sonicFoam, you need to increase the grid size (and consequently reduce time step) a lot, since this solver is much more diffusive than rhoCentralFoam.