Layermesh classes

Layermesh provides the following main Python classes for representing meshes and mesh components.

• mesh: class for a layer/column mesh

• node: class for a 2-D horizontal mesh node

• column: class for a mesh column, defined by a list of node objects

• layer: class for a mesh layer, defined by its top and bottom elevations

• cell: class for a mesh cell at a particular layer and column

For full documentation of these classes, see the Layermesh API.

The mesh class

A mesh object represents an entire mesh.

It has list properties containing its nodes, columns, layers and cells. These are called node, column, layer and cell respectively, and their elements are all objects of the appropriate type.

The node class

A node object is defined mainly by its position property pos, a numpy array of length 2, representing its horizontal location. It also has a column property, a set of the columns the node belongs to.

The column class

A column object is defined mainly by its nodes, which are stored in its node property - a list of node objects. It also has a neighbour property, a set of the neighbouring columns (those which share a face).

A column object also has layer and cell list properties, containing the layers and cells in the column. Note that different columns may have different numbers of layers, as the upper layers in the mesh may be incomplete, to represent e.g. surface topography.

Columns also have geometric properties derived from their node positions, e.g. area and centroid, and a surface property, which is the elevation of the top of the column.

The layer class

A layer object is defined mainly by its top and bottom properties, which are scalars representing the top and bottom elevations of the layer.

A layer object also has column and cell list properties, containing the columns and cells in the layer, as well as a column_cell property, for locating layer cells by their column index. Note that different layers may have different numbers of columns, as the upper layers may be incomplete.

Each layer in a mesh has above and below properties, which are the layer objects above and below that layer, if they exist. If not (e.g. for the below property of the bottom layer), they have the value None.

Layers also have geometric properties derived from their top and bottom elevations, e.g. centre and thickness.

The cell class

A cell object is defined by its layer and column properties, which are the layer and column objects corresponding to the cell.

Cells have geometric properties such as volume and centroid. Other useful properties can be accessed via the column and layer properties. For example, for a cell object c, the horizontal area is given by c.column.area, and its vertical height is given by c.layer.thickness.

A cell also has a neighbour property, which is a set of its neighbouring cells, i.e. those with which it shares a face (either horizontal or vertical). The cell immediately above or below any cell can be found using its above and below properties. These return None if there is no cell respectively above or below that cell.

Index properties

Instances of the node, column, layer and cell classes all have an index property. This represents their index in the corresponding list in the mesh they belong to.

For example, for a column col which is part of a mesh m, col.index gives the index of col in the m.column list.