## Solver Options

Note: Variable names enclosed in parentheses refer variables used in VS2DH documentation.

Relaxation parameter (HMAX): Generally in the range of 0.4 to 1.2. A value of 0.7 often works well. Try a smaller value if the simulation fails to converge.

Minimum iterations per time step (MINIT): Normally set to 2. The simulation will always perform the specified minumum number of iterations in each time step.

Maximum iterations per time step (MAXIT): If the number of iterations in a time step reaches this value, the iteration will restart from the beginning of the time step using a reduced time step size. If convergence is not achieved after 3 successive time step reductions, the simulation is considered to have reached convergence failure. Must be less than or equal to 200. Best computational efficiency is usually obtained with a value of about 100.

Stop simulation at convergence failure (ITSTOP): Select this option (recommended) to stop the simulation at convergence failure. Deselect this option to advance to next time step despite convergence failure. Note Deselecting this option could yield erroneous simulation results.

Maximum number of time steps (NUMT): The simulation will stop when number of time steps reaches this value.

Closure criterion for head (EPS): [L]. The iterative scheme for solving the flow equation is considered to have converged if, for all cells, the change in head from one iteration to the next is less than this value. In general as the value of EPS is decreased, the accuracy of results is improved and computational effort is increased. If the simulation fails to reach convergence then the user may wish to increase EPS.

Closure criterion for temperature (EPS1): [M]/[L]3. The iterative scheme for solving the transport equation is considered to have converged if, for all cells, the change in temperature from one iteration to the next is less than this value.

Closure criterion for velocity (EPS2): [L]/[T]. The outer iteration loop for the flow and transport equations is satisfied if, for all cells, the change in velocity from one outer iteration to the next is less than this value. When the outer loop is satisfied, the simulation proceeds to the next time step.