This section describes the background in applying the correction form to the discretized momentum equation.

The correction form of the discretized momentum equation is used by default (and can be disabled using the solve/set/advanced/correction-form text command, though this text command will be removed in a future release), as described in Using the Correction Form of Momentum Discretization in the User's Guide.

Discretizing a conservation law, often referred to as a transport equation, yields a linear system of equations for the iteration in the following form

(23–71)

Here are the transported variable cell values, are the coupling coefficients between left and right states, , and are the cell source terms. Without loss of generality this is written without under-relaxation and transient terms, and is referred to as the level form.

By defining the correction from iteration n-1 to iteration n as:

(23–72)

Equation 23–71 can then be rewritten as

(23–73)

which is referred to as the correction form (or delta form) of the discretized equation.