How to wisely choose a Courant Number?

Though my Courant number is less than one, in transient cases like lid-driven cavity flow etc, the courant number changes to greater than one, after a few timesteps/iterations making my solution not converge. How do I know beforehand if my solution will converge/diverge as the Courant number is changing with every iteration?

OpenFOAM 25-11-21, 12:30 a.m. Krishna_Deshmukh


What you need is dynamic time-stepping. In OpenFOAM, you can specify the maximum Courant number you'd want and the solver automatically calculates the time-step after each iteration based on the specified Courant number. You can look for the following keywords, which are to be specified in the controlDict.

adjustTimeStep, maxCo, maxDeltaT


25-11-21, 2:11 p.m. ashleymelvin

21-03-22, 7:50 p.m. geebranz

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