Numerical parameters

Transport equations for all chemical species are formulated together with boundary conditions originated from the chemical reactions. The formulation leads to the nonlinear equations system. The linearized system is solved iteratively by the same linear solver what is used for the temperature equation, see Computation -> Numerical Parameters -> Forward dialog tab.

The numerical parameters applied for the solution procedure are

These parameters are entered in the dialog window Computation -> Numerical Parameters -> Species dialog tab.

No underrelaxation is usually required for the execution of the chemical model. It means the value 1 of the underrelaxation may be appropriate. If the stability problems occur during the iterative solution run, the underrelaxation value should be reduced.

The parameter Desired residuum means the relative decrease of the overall residual of the equations system. Here the value of 1.e-9 is usually sufficient if equations are solved the first time.

The required number of iterations is problem dependent, it depends also on the applied underrelaxation value. For the problem size about 30000 nodes and 5 transported species with 4 heterogeneous chemical reactions in two transport media, about 100 iterations was enough. That corresponds to a several minutes execution on a single PC.