Hi,

For a transient simulation, we have to set the time step size in Run Calculation. This time step is based on the CFL-Number and the value of c depends on the type of solver used (explicit or implicit). The parameter are: u for the maximal velocity** of the fluid**, delta t the time step and delta x the minimal cell size.

In order to Preview the Mesh Motion, we have to give a time step size too. Is this time step based on the CFL-Number too, in order to avoid the negative cells? The velocity u in this case is then the maximal velocity **of the moving part.**

Is there then an physical time step and a numerical time step?

To obtain correct results and avoid negativ cells too, should I choose the minimal time step for the running the simulation or are the two times the same?

Regards,

Maxime