4.4. Processing

In the processing stage, the time step was set at 0.2 s, the number of steps was 1800, and the maximum number of iterations for one step was 10.

The simulation was performed on a Pentium IV, DualCore 6400, 2.4 GHz system with 4 GB RAM; for 6 min of simulation and a total number of 18,000 iterations, the computing time was approximately 12 h.

In order to prevent the equation coefficients from changing too quickly, the change in dependent variables from one iteration to another was slowed by "relaxing" them. Thus, the linear relaxation method was used for the control of the CFD simulation in order to maintain its stability; Table 3 presents the values of the relaxation factors for the different physical parameters.


Table 3. Linear relaxation factors.

In this CFD simulation, the convergence criterion was selected so that the residues remained lower than 10�<sup>6</sup> .
