[lb0331]

Can someone solve these problems for me? I am using fluent to simulate DES of orificles, and the maximum Mach number after exit can reach 1.5. I am using a density-based implicit solver. Due to the fast flow rate, if I want to ensure that CFL is less than 1, my time step will be extremely small, and my existing calculation conditions cannot be met. My confusion lies in the following points
(1) For implicit solution, CFL can be set in the control surface plate, increasing CFL can speed up convergence in steady computation, but what role does it play in unsteady computation, and it seems impossible to monitor the number of CFL. Changing the CFL does not seem to have an effect on the total simulation time while keeping the time step size and time step constant.
(2) For implicit solutions, does the choice of time step necessarily require CFL to be less than 1? Is there a looser value? How to choose the appropriate maximum number of iterations/time steps?
Thank you for your answer. I would appreciate it.