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Changing Simulation Options at Runtime in FLOW-3D

Our Development Note this issue highlights the new interactive runtime user interface feature to be released in FLOW-3D Version 9.3.

It is common for a simulation to need a change in the numerical settings to make it run more efficiently. There could be more than one reason to change the settings, e.g., poor convergence, a small time-step size, to implement a mentor tip, or just an omission in the model setup. At any rate, the simulation would have to be stopped and either restarted or rerun from the beginning with the new settings, causing inconveniences and lost time, and, in case of a restart simulation, post-processing would have to be done with multiple results files.

The new Runtime Options tool is designed to help in such situations. It allows the user to change most of the numerical options during the simulation, without the need to stop or even pause it. All it takes is to open the Runtime Options panel in the Simulate window, review the current options and decide what needs to be modified. Once the changes are chosen, the user sends them to the solver, which then reviews the new settings and applies them.

The runtime options include all those available from the Numerics panel in Model Setup (pressure solvers, implicit options, time-step control, and so on) plus the finish time, limited compressibility coefficients and viscous boundary conditions at walls. The user can also define the time at which to apply the changes, if not immediately. This can be helpful to tie the change to a specific event during the simulation.

FLOW-3D screenshot of the new Runtime Options panel
New Runtime Options panel

A restart data edit can be requested at the time the change takes place to allow the user to examine the solution just before the modification, and to enable a restart calculation from that time in case the solver terminates. If the changes are beneficial, the user can save them to the original prepin project file.

There is no limit on how many or how often changes can be made during a simulation. For example, if a switch to the GMRES pressure solver resulted in a slower execution, the user can revert back to the original solver. A log file is kept of all the changes and the time of their application.

The flexibility of this new GUI feature puts the responsibility on the user to be careful with making changes. A safety feature is built into the Runtime Options tool that allows the user to revert back to the initial settings as defined in the original project.