DarcyConstant

coupling parameter for porous media [kg/(s*m^3)]

Define the DarcyConstant $ \tilde{\beta}$ for the material with index $Material$ :

DarcyConstant($Material$) = RightHandSideExpression

The law of Darcy models the influence of a porous medium A on a fluid B that flows through A by the addition of a momentum source term to the standard fluid flow equations of B. See EquationsToSolve for the integration of this source term to the momentum equation and TwoPhaseDarcy for a more specific example of using Darcy within MESHFREE. The DarcyConstant regulates the permeability of the porous medium and thus influences the magnitude of this source term.

Isotropic materials

If in the RightHandSideExpression one argument is given, e.g.

DarcyConstant($Material$) = ( 1e3 ) # constant Darcy constant of 1e3 kg/(s*m^3)

then the porous material is assumed to be isotropic. Thus, $ \beta$ in EquationsToSolve can be viewed as a scalar quantity.

Anisotropic materials

For anisotropic permeability, the DarcyConstant can be set for three perpendicular directions. The RightHandSideExpression then takes twelve arguments, e.g.

DarcyConstant($Material$) = ( &bx&, 1, 0, 0, ... # Darcy constant in x-direction, unit vector x &by&, 0, 1, 0, ... # Darcy constant in y-direction, unit vector y &bz&, 0, 0, 1 ) # Darcy constant in z-direction, unit vector z

In this case $ \beta$ in EquationsToSolve represents a matrix which is constructed from the supplied constants and directions.

Inertial contribution

To extend the Darcy model by an inertial contribution, see ForchheimerConstant.

Notes

Despite the naming convention, %ind_betaDarcy% will not store $ \tilde{\beta}$, but $ \beta = \frac{\tilde{\beta}}{\rho}$ in EquationsToSolve
For points in DROPLETPHASE chambers, DarcyConstant does not define $ \tilde{\beta}$, but $ \beta$ directly (no internal division by density). The unit of the supplied constant therefore has to be [1/s].