Changes between Version 130 and Version 131 of doc/app/initialization_parameters
- Timestamp:
- Nov 8, 2010 2:32:35 PM (14 years ago)
Legend:
- Unmodified
- Added
- Removed
- Modified
-
doc/app/initialization_parameters
v130 v131 628 628 {{{#!td 629 629 Time step limiting factor.\\\\ 630 In the model, the maximum allowed time step according to CFL and diffusion-criterion dt_maxis reduced by [#dt dt] = dt_max * '''cfl_factor''' in order to avoid stability problems which may arise in the vicinity of the maximum allowed timestep. The condition ''0.0'' < '''cfl_factor''' < ''1.0'' applies.\\\\630 In the model, the maximum allowed time step according to CFL and diffusion-criterion [../d3par#dt_max dt_max] is reduced by [#dt dt] = dt_max * '''cfl_factor''' in order to avoid stability problems which may arise in the vicinity of the maximum allowed timestep. The condition ''0.0'' < '''cfl_factor''' < ''1.0'' applies.\\\\ 631 631 The default value of '''cfl_factor''' depends on the [#timestep_scheme timestep_scheme] used:\\\\ 632 632 For the third order Runge-Kutta scheme it is '''cfl_factor''' = ''0.9.''\\\\ … … 1734 1734 If the user assigns '''dt''' a value, then the time step is fixed to this value throughout the whole run (whether it fulfills the time step criteria or not). However, changes are allowed for restart runs, because '''dt''' can also be used as a [../d3par run parameter].\\\\ 1735 1735 In case that the calculated time step meets the condition\\\\ 1736 '''dt''' < 0.00001 * [ #dt_max dt_max] (with dt_max = 20.0)\\\\1736 '''dt''' < 0.00001 * [../d3par#dt_max dt_max] (with dt_max = 20.0)\\\\ 1737 1737 the simulation will be aborted. Such situations usually arise in case of any numerical problem / instability which causes a non-realistic increase of the wind speed.\\\\ 1738 1738 A small time step due to a large mean horizontal windspeed speed may be enlarged by using a coordinate transformation (see [#galilei_transformation galilei_transformation]), in order to spare CPU time.\\\\