By default the Porosity, εp (dimensionless) is taken
From material. Select
User defined to enter a different value or expression.
Select an option from the Velocity field list to specify the convective velocity along the fracture. For a consistent model, use a Fracture Flow feature in a Darcy’s Law interface to compute the fluid flow velocity in the fracture.
For User defined, enter values or expressions for the velocity components in the table shown.