Differencing operator along z-direction to total (including hanging) z faces

This property constructs a differencing operator along the z-axis that acts on cell centered quantities; i.e. the stencil for the z-component of the cell gradient. The operator computes the differences between the values at adjacent cell centers along the z-direction, and places the result on the z-faces. The operator is a sparse matrix $$\mathbf{G_z}$$ that can be applied as a matrix-vector product to a cell centered quantity $$\boldsymbol{\phi}$$, i.e.:

diff_phi_z = Gz @ phi


By default, the operator assumes zero-Neumann boundary conditions on the scalar quantity.

Returns
(n_total_faces_z, n_cells) scipy.sparse.csr_matrix

The stencil for the z-component of the cell gradient