interFOAM courant number is less than hand calculated
 

I am running a simulation with gas and water mixture using interFOAM. The smallest cell in my mesh is approximately 6e-5m. By considering a courant number of 1 I calculated that the minimum timestep should be 3.27e-4s. However when I run the simulation the timestep adjusted by the solver is in the order of e-7. I want to know why this happens ?

What velocity did you use to manually calculate your time step?

Velocity at the inlet, which is also what is initialized for the whole domain before the simulation begins

The velocity used to compute the Courant number is the local velocity in the cell, this is probably why you get different results.

There is a function object allowing to write the Courant number as a volume field if you want to investigate where is your maximum Courant number:

• foundation branch: https://github.com/OpenFOAM/OpenFOAM...No/CourantNo.H
• ESI-OpenCFD branch: https://develop.openfoam.com/Develop...No/CourantNo.H

Thank you for the explanation