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GfsLayers is used to set the number of layers in the GfsRiver Saint-Venant solver.

The syntax in parameter files is

GfsLayers NL

where NL is the number of layers. In addition to the default variables defined by GfsRiver, GfsLayers will define additional variables called U0, U1, ..., UNL-1, V0, V1, ..., VNL-1, for the components of the momentum in each layer. For the moment, the layers are evenly spread in the vertical, so that the thickness of each layer is P/NL. The velocity vector in a given layer will then be (Ui*NL/P,Vi*NL/P). By convention the bottom layer has index 0.

If a tracer is defined using e.g.

VariableTracer T

GfsLayers will also define the corresponding variables T0, T1, ..., TNL-1 which will contain the "mass" of tracer in each layer i.e. the concentration for a given layer will be Ti*NL/P.

Boundary conditions can be set either "locally" for each layer (by setting boundary conditions on individual layer variables), or "globally" by setting conditions on U or V.


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