Fan boundary condition.
 

Hi, I am wondering how the Fan BC really works in terms of imposing a delta pressure. As far as I understood it looks for the normal velocity vector, in the fan surface mesh, to determine the direction of the flow. Subsequently it imposes the delta pressure on the correct side of the adjacent volumetric mesh. I am facing a problem because my simulation has a big recirculation bubble due to the high curvature of the duct and whenever a turn on the fan BC it seems that it gets worse. I think that the fan BC is putting a Delta P for one side of the adjacent volumetric mesh (for the going flow â€" positive vectors on the fan surface mesh ) and also putting another delta P in the opposite side of the adjacent volumetric mesh ( for the coming flow â€" negative vectors on the fan surface mesh ). Does anybody knows how to prevent it, and make the fan do the right thing, that is imposing the delta P in one single direction?