645 | | These velocities are calculated from the resolved and subgrid-scale TKE using the Monte-Carlo random-walk method described by Weil et al. (2004, JAS, 61, 2877-2887). When using this method, the timestep for the advancement of the particles is limited by the so-called Lagrangian time scale. This may be smaller than the current LES timestep so that several particle (sub-) timesteps have to be carried out within one LES timestep. In order to limit the number of sub-timesteps (and to limit the CPU-time), the minimum value for the particle timestep is defined by the package parameter [#dt_min_part dt_min_part].\\\\ |
646 | | Setting '''use_sgs_for_particles''' = ''.T.'' automatically forces [../inipar#use_upstream_for_tke use_upstream_for_tke] = ''.T.''. This inhibits the occurrence of large (artificial) spatial gradients of the subgrid-scale TKE which otherwise would lead to wrong results for the particle advection. |
| 645 | These velocities are calculated from the resolved and subgrid-scale TKE using the Monte-Carlo random-walk method described by Weil et al. (2004, JAS, 61, 2877-2887). When using this method, the timestep for the advancement of the particles is limited by the so-called Lagrangian time scale. This may be smaller than the current LES timestep so that several particle (sub-) timesteps have to be carried out within one LES timestep. In order to limit the number of sub-timesteps (and to limit the CPU-time), the minimum value for the particle timestep is defined by the package parameter [#dt_min_part dt_min_part]. |