MULTI / 028
VOF & Free-Surface Time-Step Advisor
Screen transient timestep against convective, capillary and gravity-wave scales before tuning interface-compression or solver controls.
Use the calculation to challenge the CFD setup.
Free-surface simulations can be limited by more than convection. Surface tension and wave propagation can introduce smaller physical timescales than the bulk-flow Courant estimate suggests.
Define the reference scale. Use values that represent the actual engineering problem.
Calculate transparently. The tool exposes the governing relation and intermediate outputs.
Compare with the solver. Look for inconsistent definitions, units or modelling assumptions.
Test sensitivity. Important CFD conclusions should not depend on one arbitrary input or discretization choice.
Move from calculation to diagnosis.
Use the result as a benchmark, then follow the relevant Technical Case or consulting capability when the actual CFD model needs deeper judgement.