The solution algorithm for the fiber equations requires a means for checking convergence of the solution. In the fiber model a simple residual is used for this purpose.

The conservation equation for a general variable at a cell can be written as

(22–18)

where

The residual computed by the fiber model is the imbalance in Equation 22–18 summed over all fiber cells.

(22–19)

This is called the absolute residual. Relative residuals are defined as the change of the absolute residuals between two subsequent iterations divided by the absolute residual.

(22–20)