Pre 2014 Blogs

SWMM 5 Variable Time Step

Posted by Robert Dickinson on January 11, 2009 at 10:46pm

Topic: The Variable time step and the Adjustment Factor. The adjustment factor lowers the internal time step used in the model. In the example model the lowering of the Adjustment factor from 75 percent to 25 percent lowers the minimum simulation time step from 20 second to 3 seconds. The inflow and outflow of the model stays the same, what changes is the computed internal time step based on the Courant CFL condition.

At each time step the minimum CFL time step is calculated based on the length of the link (delta x), the ending velocity at the last time step in the link (V) and the ending link depth at the last time step (D).