I am using the porous jump condition on a cylindrical filter paper, where flow direction is variable. How does the porous jump condition choose the direction in which to apply the pressure drop? Is it based on face normals, or flow direction?
Porous jump conditions are used to model a thin “membrane” that has known velocity (pressure-drop) characteristics. By default, the pressure drop is applied in the direction of flow, so this can be variable throughout the simulation.
To have the porous jump model apply pressure drop according to face normals, set the rpvar:
(rpsetvar 'jump/orient-zone-based-on-flow? #f)