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

Issue

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

Solution

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.