 ## General

#### Can I increase the Volume Porosity value in a Porous Domain without affecting the pressure drop, assuming everything else remains the same?

• FAQ
Participant

In some cases, a low Volume Porosity value can cause convergence problems when the flow is parallel to the Fluid-Porous interface. Convergence can sometimes be improved by using a higher Volume Porosity value. This won’t change the calculated pressure drop if the Loss Model is formulated in terms of the Superficial Velocity. For example, if the Loss Model is based on Linear and Quadratic Resistance values, the pressure drop is expressed as: Delta P = K*delta_X * V^2 Here, K is the Quadratic Resistance Coefficient based on Superficial Velocity, delta_X is the thickness of the porous media and V is the Superficial Velocity. From this equation, we can see that the Volume Porosity will not influence the pressure drop. It is only when the Loss Model is formulated from the True Velocity that the pressure drop will change, since the True Velocity depends on Volume Porosity. Note that in many cases it is not necessary to use a Porous Domain; a sub-domain with a Momentum Loss model can often be used instead. 