Area Porosity represents the fraction of physical area that is available for the flow to go through. The default setting is Isotropic.

Volume Porosity is the local ratio of the volume of fluid to the total physical volume.

Porous losses can be included using an isotropic or directional loss model. In each case, the loss is specified using either linear and quadratic coefficients, or permeability and loss coefficients. When specifying the loss coefficients, it is important to properly set the Loss Velocity Type.