[francescomarra]

Dear Foamers,

I would ask for your help to understand what I am doing stupid.
My experience, everybody should be able to quickly reproduce, start with the tutorial in $FOAM_TUTORIALS/compressible/rhoPisoFoam/les/pitzDaily (I am actually running version 1.7.1 from CentFOAM).

The solution obtained with the set-up already fixed in the tutorial gives non-physical results. Looking into the log it is immediately discovered that a too large Courant number is reached. A physically reasonable results is obtained changing the time step control to:
adjustTimeStep yes;
(you can stop the simulation very early, say endTime = 0.05).

Now, if you newly fix the time step to a constant value less than the minimum time step of the previous simulation, so that the max Courant number should remains within the stable range, the results appear to be newly non-physical. Actually velocity increases so much that Courant newly increases above the stability limit.

Therefore it seems that I am unable to increase the accuracy of the time discretization by decreasing the time step.

Please help me to elucidate this behaviour.

Kindest regards,

Franco