| | 109 | |
| | 110 | These variables control the timesteps the simulation takes. |
| | 111 | |
| | 112 | * '''{{{cfl_vars}}}''': This is a three-element array of floating point numbers. Each one has a different function: |
| | 113 | * ''{{{cfl_vars(1) -- Max CFL}}}'': The maximum allowable [http://en.wikipedia.org/wiki/Courant–Friedrichs–Lewy_condition CFL] number the system can have. If {{{cfl_vars(1)}}} is exceeded, then the simulation will restart the current step with a smaller timestep. The maximum CFL value should be between 0 and 1. The most common value for the maximum CFL is {{{1}}}. |
| | 114 | * ''{{{cfl_vars(2) -- Target CFL}}}'': The target [http://en.wikipedia.org/wiki/Courant–Friedrichs–Lewy_condition CFL] number. Lower CFLs produce more accurate results, but also require more timesteps. Target CFL values of {{{.2}}} to {{{.3}}} are common for 3D problems, whereas 2D problems can go as high as {{{.4}}}. |
| | 115 | * ''{{{cfl_vars(3) -- CFL relaxation}}}'': A coefficient between 0 and 1 that limits the degree to which the timestep size can change from one step to the next. This prevents extreme timestep variations which could otherwise kick the CFL down to 0 or above the maximum. A CFL relaxation parameter of 1.0 is basically the same as having no relaxation parameter. |
