Run error
 

Hello, I set a working condition with a fixed time step, but the following contents are always displayed during operation{‘EMERGENCY STOP -- velocities exceeding critical value N 61’}. Then set the value of n61 large enough,, but the above situation still occurs. How should I adjust it?

When you encounter an error due to "velocities exceeding N 61", it means that something is wrong with your simulation, resulting in unphysical high velocity values.
You need to inspect what is happening to your simulation, say, in Paraview.
Since you use a constant time step, I believe this is the source of your problem.
See if the problems goes away when you use the CFL criterion instead. And then, if you really wish to use a constant time step, use the time step that is of the order of that seen in the simulation with the CFL-based time step.

Ok, thank you very much!