[prapanj]

My question may be silly. In the controlDict file, I only see an option to set dT. Is there anyway I can specify a Co number and let dT vary, for a steady state problem? I am sure there is a way. But I haven't some across any tutorial that explains this.
Thanks in advance

[lin]

For the steady case,you do not need to worry about the Co number.

[roth]

Sometimes you need to use pseudo-transient solvers to get to a steady-state so one option is to run a transient solver and use the CoEuler scheme.

In fvSchemes:

ddtSchemes
{
// default backward;
default CoEuler phi maxCo 0.5;
}

If you have a sufficiently large timestep size set in your controlDict, the above it will use localized, smaller timestep sizes based on maintaining Courant less than 0.5.

Physically it doesn't make much sense but if all you're trying to do is to get to steady state it might be faster than using the same timestep size everywhere in your domain.

The alternative is to add adaptive time-stepping to your solver.

Michael