When running a natural convection model, especially with many cells, the solver takes a long time for the early iterations. Once the iteration number reaches say 30 or so, the solver proceeds much faster. I think that if I were to set a non-zero starting velocity for the fluid cells the solver would iterate faster. The ability to set a starting velocity is default in Flotherm, where the starting velocity for natural convection models is 0.2 m/s.

Can a starting velocity be set with Flow Simulation? If so, how? Please note - I'm not asking about setting an initial velocity, which is where there is a prescribed flow field, but how to set a starting velocity so that the solver can iterate faster for natural convection models.

David

in this case define the fluid volume of the model and use a local initial condition and disable the solid that defines this volume

(because I think you're right, this would set that the boundary of an external simulation was always moving at this velocity)