| 69 | 69 | In order to speed-up performance, the Poisson equation for perturbation pressure (see [[psolver]]) can be called only at the last substep of multistep Runge-Kutta timestep schemes (see [[timestep_scheme]]) by setting '''call_psolver_at_all_substeps''' = ''.F.''. In many cases, this sufficiently reduces the divergence of the velocity field. Nevertheless, small-scale ripples (2-delta-x) may occur. In this case and in case of non-cyclic lateral boundary conditions, '''call_psolver_at_all_timesteps''' = ''.T.'' should be used. |
