Porous zone undergoing motion: translation/rotation
 

Hi there,

I am simulating a steady case where I have a porous zone that is moving. It can either be that the zone is translating or rotating. Now if I apply an explicit porosity source through fvOptions on this supposed moving cellzone, the application of the porosity would be incorrect since the porosity is applied in the absolute frame of reference. My work around for that currently was to use another fvOption source: meanVelocityForce to essentially force the cellZone to translate with the velocity the zone would be moving. For the most part, it seems to be working as intended but is clearly not robust (simulation diverges) to different porosity values. I could see from the source code that porosity has the option of specifying a relvativeVelocity flag (or porousRelVelocity_) which when active in conjunction with the mesh_.moving() flag passes the relative velocity to computing the porosity. So, the question would be how to activate this setting in the solver? Do I need to consider mesh motion using dynamicMeshDict (which seems computationally expensive and not sure if works for steady simulations) or is there a more straightforward approach?

Thanks!

P.S. Not any OF version specific and not concerned with coding up a new fvOption if needed.