Solution Monitoring

The STORM Solution Monitor program provides “instant feedback” from the STORM solver regarding the status of your solution during execution. With this data, you can “fine tune” the solver parameters and therefore achieve the most efficient solution convergence. Both solution residuals and computed values of the dependent variables (“spot values”) are displayed on the Solution Monitor. Key solver parameters can also be "dynamically" adjusted, thereby avoiding the trouble and expense of halting your solution, returning to the CFD2000 interface, making the required changes, and then restarting your simulation.

Runtime Residuals

Residuals provide a qualitative measure of convergence, and are computed by summing the current errors for each equation over the entire computational domain. As such, they provide an “at a glance” picture of the global state of the solution.

For a converging solution, the residual traces for all variables should generally decrease in magnitude as a function of time, with a rate that often becomes linear when plotted on the default logarithmic scale. Once the solution has fully converged, the residual plots traces should become fairly “flat,” with a very small incremental change (as indicated by the values listed under the Change column to the right of the plot) between updates.

Spot Values

The Runtime Spot-Value Plot shows color-coded traces of the instantaneous values of each active dependent variable from the start of the current run to the most recent update (usually, the current time step). Like the Runtime Residual Plot described above, the ordinate of this plot represents time, and the abscissa shows the computed values of the individual variables normalized by the quantities listed under Value.

Spot value monitoring is particularly useful for observing portions of your flow domain that may be responsible for hindering solution convergence. Examples of such potential problem areas include regions just upstream of any flow outlets and the “turnaround” or vortex shedding regions located downstream of flow obstacles. You can also use this technique as a “virtual measurement instrument” to observe the dynamic evolution of a particular variable of interest.