Conditions governing time step

I know in EFDC model and any other numerical model the time step is mostly governed by the Courant condition. I believe in EFDC the sum of the directional courant numbers must be less than or equal to unity. I am wondering is there any other parameters or conditions that govern the time step and the convergence of the EFDC model ?



Hi John,

The hydrodynamics are important in determining the time step - horizontal momentum and diffusion should be looked at in particular. The Courant number is only one issue. We usually use the Courant-Fredrich-Levy (CFL) time step, which may be found under Model Metrics in Viewplan. Here the CFL time step is computed for each cell and displayed. This is a good guide to the appropriate time step, especially if using the two time level solution.