Primary unknown is the groundflow_pressure .
Further notation:
group_groundflow_density;
group_groundflow_compressibility;
group_groundflow_permeability;
space coordinate;
material velocity (if present);
force_element_volume (pressure source).
The equation is given for space coordinates following material
velocities
(if present).
The groundflow velocities (see groundflow_velocity) follow from:
In case of gravity, the initial nodal pressures should be initialized in the pressure part of the node_dof records, and the gravity force should be included in the pressure part of the force_element_volume record.
The above naming for ,
and
is somewhat misleading with respect to conventional
naming in groundwater flow analysis.
To connect better to conventional naming, we remark the following:
where
is the compressibility of water and
is the porosity.
where
is the permeability and
is the unit weight of water.