16.8.3 The Stiff Chemistry Solver

ANSYS FLUENT has the option of solving intraphase and interphase chemical reactions with a stiff chemistry solver. This option is only available for unsteady cases, where a fractional step scheme is applied. In the first fractional step, the multiphase species Equation  16.8-1 is solved spatially with the reaction term ${R_{i}}^q$ set to zero. In the second fractional step, the reaction term is integrated in every cell using a stiff ODE solver.