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The flux at a given face, for example the + *k*
-face,

is defined using this stencil:
in the Asymmetric Method. The Support Operator Method uses all seven unknowns
within a cell to define the face flux.
Each cell has a cell-centered conservation equation which involves all six
face fluxes, and gives a stencil which includes all seven unknowns within
the cell (in both methods).

To close the system, an equation relating the fluxes on each side of a face
is added for every face in the problem. This gives the following stencil:
in the Asymmetric Method. The Support Operator Method uses all thirteen
unknowns within a cell-cell pair to define the face equation.

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**Up:** Diffusion
** Previous:** Diffusion Discretization Method Properties
Michael L. Hall