Hello everyone. I read Jeff’s explanations for DESGRIDSEARCH_IMAX, DESGRIDSEARCH_JMAX, DESGRIDSEARCH_KMAX in the forum ‘The number of cells (des grid) does not need to be defined. If left blank, it will be set so the grid spacing is three times the max particle diameter. You can define it to change the des grid spacing. Larger spacing means less des grid cells but more particles per cells. It is recommended to leave it blank. If you want to change it, you may need to experiment to see if it helps or hurt the speed of the simulation.’."Search grid partition (optional)" in solids pane, DEM sub-pane - #2 by jeff.dietiker
But I have some confused. I see in the code ‘ltempdx = xlength/desgridsearch_imax’, which suggests that the larger the desgridsearch_imax, the finer the DES grid. But I see that you explained that the larger the value, the more spacing the des grid has.
(1) So in order not to miss collisions of high speed particles, should the value be bigger or smaller?
(2) What does it mean that the DES mesh is thicker or thinner?
Hello everyone. I still don’t understand the significance of DES mesh size for particle collision after checking the code. Could someone please answer my confusion?
DESGRIDSEARCH_IMAX is number of cells, not cell spacing, as the documentation indicates. Spacing is the reciprocal of number of cells, as you see in the code.
To avoid missing collisions we suggest lowering Max steps between neighbor search (neighbor_search_n). It is not usually necessary to modify DESGRIDSEARCH_[IJK]MAX. See DEM Particles with unrealistic high velocity - #12 by gbotha
A “thinner” mesh generally means finer grid resolution with more cells packed into the same volume.
Thanks Charles. Thinner grid or bigger ‘DESGRIDSEARCH_[IJK]MAX’, does it mean to be able to search more neighbours now? Because when the particles are very small, the default number of DES grids is very high. At this point I have to manually specify the number of DES meshes, but I’m not sure how the size of the DES mesh affects the motion or collision of the particles.