Extrusion meshed resistance region defined with Pressure-Flow rate curve fails to run


A distributed resistance region defined with a pressure-flow curve is meshed with an extruded mesh. The analysis stops after the first iteration with this message in the Sol file: 

#IND error



This is a limitation. A distributed resistance region that is extrusion meshed cannot be defined with a head-capacity table.

The work-around is to either mesh the region with tetrahedral elements or to use a different resistance definition.

The problem is that distributed resistance regions assume that the mesh is conformal and that nodes between a distributed resistance region and a fluid region can be used to define inlets and outlets, etc., through the model. Since the extrusion mesh is non-conformal, no inlet or outlet is found, the resultant flow area is zero, and there are no surfaces on which to evaluate the pressure change. When the solver attempts to compute a K factor, a divide by zero error occurs:

velocity = Q / area = 0 / 0 (when no inlet or outlet is found because of a non-conformal extruded mesh)

K = dP / 0.5 * rho * velocity^2 = 0 / 0

The alternative is to use a constant K value when the resistance region is mesh with an extruded mesh because that value will be applied without the need to compute flow areas, pressure drops, or flow rates.


Simulation CFD