CFL-Number
 

I know CFX is an implicit solver nevertheless i wanted to know which best practice range for CFL number does exist for multiphase flows.
thanks

Julienne

There's no recommended range. For example, as you refine your mesh your CFL number would change, but in general you wouldn't need to adjust your timestep.

From theory we know, that an implicit solution is stable independent from the time step. I guess does not include source terms from reaction or multiphase. For that reason in that applications you may require smaller time steps.

To expand on the previous comments: Explicit solvers have a stability limit at a Courant number of 1. You simply can't go faster than that. But CFX is an implicit solver so this restriction does not apply (but a very common mistake is to forget this and run CFX with a Courant number <1).

So the timestep required for CFX should be determined with a sensitivity study on a case by case basis. The allowable timestep is often much bigger than 1.0, but exactly how big is OK depends on the simulation.