discretize.TreeMesh.average_node_to_cell

TreeMesh.average_node_to_cell

Averaging operator from nodes to cell centers (scalar quantities).

This property constructs a 2nd order averaging operator that maps scalar quantities from nodes to cell centers. This averaging operator is used when a discrete scalar quantity defined on mesh nodes must be projected to cell centers. Once constructed, the operator is stored permanently as a property of the mesh. See notes.

Returns:

(n_cells, n_nodes) scipy.sparse.csr_matrix

The scalar averaging operator from nodes to cell centers

Notes

Let \(\boldsymbol{\phi_n}\) be a discrete scalar quantity that lives on mesh nodes. average_node_to_cell constructs a discrete linear operator \(\mathbf{A_{nc}}\) that projects \(\boldsymbol{\phi_f}\) to cell centers, i.e.:

\[\boldsymbol{\phi_c} = \mathbf{A_{nc}} \, \boldsymbol{\phi_n}\]

where \(\boldsymbol{\phi_c}\) approximates the value of the scalar quantity at cell centers. For each cell, we are simply averaging the values defined on its nodes. The operation is implemented as a matrix vector product, i.e.:

phi_c = Anc @ phi_n