## Description

The keyword $FLOWLINEARITY enables the definition of the parameters for describing the non-linear form of fluid flow in porous media. Currently it is only active for Forchheimer flow, which occurs when the inertial force is larger than the viscous force. A non-linear term is added to the Darcy’s law and a non-Darcy coefficient is used as the non-linear parameter.

## Parameters

Under the keyword $FLOWLINEARITY, the first parameter indicates the model type that is applied, followed by its model parameters. In the example below, the first parameter i.e. ‘5’ defines a model type that only the coefficient for the non-linear term of the Forchheimer equation should be given, since the coefficient for the linear term is assumed to be the reciprocal of the hydraulic conductivity. The coefficient for the non-linear term is defined by the second parameter i.e. 1e8 (m^{-2}s^{2}).

## Examples

### RWPT\Forchheimer

#MEDIUM_PROPERTIES ... $FLOWLINEARITY 5 1e8 ... #STOP