Inflow/Outflow rates along lines

Inflow/Outflow rates along lines
SPRING-help >> Description oft he data types >> Boundary conditions and source terms >> Flow boundary conditions >>

Attributes:

RAND ([(m³/TU) per metre or m² of the polyline] (node-wise)

RANQ [(m³/TU) for the entire polyline] (node-wise),

RANX [(m³/TU per m(x0) or m(x)*m] (node-wise)

 

The RAND, RANQ and RANX attributes can be used to specify inflows and outflows along a polyline. As with a water balance, inflows are positive and outflows are negative.

By means of inserting an asterisk (*) in the 16th column of the model file, the thickness is taken into account when converting the rate to node values (currently only for horizontal models).

RAND without '*':

  • The assigned value represents a rate per metre along the polyline. The length is calculated from the distance between the nodes. For each node of the polyline, an appropriate inflow or outflow rate is calculated according to the corresponding section lengths for that node.

RAND with '*':

  • The assigned value represents a rate per square metre (m²). The area is calculated from the distance between the nodes multiplied by the width (thickness) of the model. The thickness is calculated as the average of the elements adjacent to the relevant polyline segment. For each node of the polyline, a corresponding inflow or outflow rate is calculated according to the proportional area.

RANQ without '*':

  • The assigned value represents a total rate for the polyline (m). The total rate is distributed among the nodes of the polyline according to the proportional lengths/distances between nodes.

RANQ with '*':

  • The assigned value represents a total rate for an area (m²). The area is calculated from the distance between the nodes of the polyline multiplied by the width (thickness) of the model The thickness is calculated as the average of the elements adjacent to the relevant polyline segment. The total rate is distributed among the nodes of the polyline according to the proportional area (distance between nodes * thickness).

RANX without '*':

  • The assigned value represents a rate per metre of the abscissa/x-axis. In contrast to the RAND data type, the line length is only calculated from the abscissa distance (x-coordinates) of the nodes. For each node of the polyline, a corresponding inflow or outflow is calculated according to the abscissa distance between the nodes.

RANX with '*':

  • The assigned value represents a rate for an area (m²) defined by the distance on the abscissa/x-axis between nodes and a thickness. In contrast to the RAND data type, the area is only calculated from the abscissa distance (x-coordinates) of the nodes, and is then multiplied by the width (thickness) of the model. The thickness is calculated as the average of the elements adjacent to the relevant polyline segment. For each node of the polyline, a corresponding inflow or outflow is calculated according to its proportional area.

The following figure shows a section of a model with various boundary inflows. The excerpt from the included *.net file example refers to this figure.

 

Example:

RAND

20.00 200, 6, 5, 11, 7

0.50 * 200, 92, 88, 60,

RANQ

300.00 1, 70, 75, 99,

RANX

1.00 * 60, 67, 76, 80,

 

The left boundary (nodes 200, 6, 5, 11 and 7) have a specified boundary inflow of 20 m³/m/TU assigned with the RAND attribute to each metre between the specified nodes.

The area seepage for the F1 area with rate 0.5 m³/m²/TU is assigned with the RAND attribute. The seepage is calculated from the distance between the nodes (200, 92, 88 and 60) multiplied by the width (thickness).

The boundary inflow on the right boundary (nodes 1, 70, 75, and 99) assigns a total rate of 300 m³/TU for the entire boundary (distributed among the relevant nodes) as the RANQ attribute.

An area infiltration for the F2 area (nodes 60, 67, 76 and 80) of 1.0 m³/m²/TU is assigned with the RANX attribute. The rate is thus defined by the distance between nodes on the x-axis, multiplied by the thickness. The F2 area can, for example, correspond to the water surface of a river, where infiltration rates are often specified in m³/km²/TU, which is then converted to m³/m²/TU.

Nodes 200 and 60 automatically receive two inflows in the above example (node 200 from the two RAND inputs, node 60 from the 0.5 RAND input and the RANX input).