## Description

The keyword $ PERMEABILITY_FUNCTION_STRAIN returns relative permeability for liquid flow process.

Four cases are implemented in the OGS, in which permeability is a function of strain (volumetric or/and equivalent plastic strain).

## Parameters

int int (int)

The first value is the case number (1, 2, 3 or 4).

For case ‘1’ one additional parameter value (curve number) is required. The curve defines the relationship between relative permeability and volumetric strain.

For case ‘2’ one additional parameter value (curve number) is required. The curve defines the relationship between relative permeability and equivalent plastic strain.

For case ‘3’ two additional parameter values (both curve number) are required. The first curve defines the relationship between relative permeability and volumetric strain if equivalent plastic strain is equal to zero. The second curve defines the relationship between relative permeability and equivalent plastic strain if the equivalent plastic strain is not zero.

For case 4 two additional parameter values (both curve number) are required. The first and second define the relationship between relative permeability and volumetric strain as well as equivalent plastic strain respectively, same as case ‘3’. But the return value is the product of the two curve values.