14.2.6 Evaluate_Gradient_Cells_Ortho_Diffusion Procedure

The Evaluate_Gradient_Cells_Ortho_Diffusion procedure evaluates the gradient of Phi at the cell centers using the specified Ortho_Diffusion Term. The gradient is not necessarily constant across a face, since the diffusion coefficient may change, but the flux is. This procedure calculates the constant flux across a face, then divides by the diffusion coefficient of the cell to get the gradient at each face. Then, averaging opposite faces results in a cell-centered gradient.

Calling syntax:

call Evaluate_Gradient_Cells (Diff_Term, Phi_MV, Grad_Cells)

Input variables:

 Diff_Term  The Ortho_Diffusion Term to be evaluated.
 Phi_MV  The Phi Mathematic Vector to use in the evaluation.

Output variables:

 Grad_Cells  The gradient of Phi vector evaluated at the cell centers.

Internal variable:

 Grad_dot_N_Faces_of_Cells  The gradient of Phi dotted with the unit normal at each face of each cell.

The Evaluate_Gradient_Cells_Ortho_Diffusion code listing contains additional documentation.

Michael L. Hall