# Input file bc

## Parameters

$Sub-keywords$CONSTRAINED

Adds velocity dependent BC. Adds possibility to give multiple constraints to one BC. Adds PRESSURE_AS_HEAD options. Can also be used with $SOURCE_TERM Syntax for the constraint can be$CONSTRAINED

VELOCITY [POSITIVE/NEGATIVE]

This will evaluate flow direction at a surface BC and discard a BC if scalar product of velocity vector and surface normal is < 0 (ie for POSITIVE not flowing into same direction as surface normal is pointing to, or vice versa for NEGATIVE). Additionally, there is the possibility to combine multiple constraints. Eg $CONSTRAINED VELOCITY NEGATIVE$CONSTRAINED

[PCS] [PrimVar?] [VALUE] [DIRECTION]

PCS can be any process (in theory) PrimVar? is the primary variable of the PCS to be evaluated VALUE is the limiting value of PrimVar? DIRECTION is SMALLER (will constrain the BC, if the value of PrimVar? is smaller than VALUE) or GREATER (opposite) Both constraints will be evaluated, if any of them is positive, the BC will be be ignored.

Example, where a given boundary condition will be constrained depending on the mass transport's concentration (here, the whole polyline will be switched off, if any node qualifies for the constraint): #BOUNDARY_CONDITION

$PCS_TYPE RICHARDS_FLOW$PRIMARY_VARIABLE

PRESSURE1

$GEO_TYPE POLYLINE PUMP1$DIS_TYPE

CONSTANT 1000