ABSTRACT
The finite element form of the equilibrium equations for the slow, steady flow of fluid through a rigid, porous solid may be obtained by application of the divergence theorem in the form of a principle of virtual power. The derivation is similar to that used to obtain the equilibrium equations of a deformable, but “dry” solid. In the case of seepage, the fluid is considered “ideal”, that is, incompressible and without viscosity. Flow occurs according to Darcy’s law. Appropriate boundary conditions analogous to specified displacements are specified node pressures. Specified flow velocity normal to a boundary is analogous to a specified force at a node. In stress analysis, forces are usually specified at the surface of a body; interior nodes are usually free of externally applied forces. In seepage analysis, a flow may be specified at an interior node to simulate fluid pumping or injection from a well.
