Pseudo Time Stepping for Mass Transport
In order to improve the solution robustness, pseudo time stepping can be used for the Transport of Concentrated Species interface when solving a stationary model. Using pseudo time stepping, a fictitious time derivative term:
is added to the left-hand side of the mass fraction equations. Here ρ is the fluid mixture density, ωi is the mass fraction (dimensionless) of species i, and is the pseudo time step. Since ωi−nojac(ωi) is always zero, this term does not affect the final solution. It does, however, affect the discrete equation system and effectively transforms a nonlinear iteration into a time step of size .
For a description of the pseudo time step term for the Navier–Stokes equations and the pseudo time step see Pseudo Time Stepping for Laminar Flow Models and Pseudo Time Stepping in the COMSOL Multiphysics Reference Manual.