I use a group of object to render grass in a particles system set on hair.
Hair dynamics is on and seem to work well except that it has no bending over the stand I use.
They rotate along their origin but they do not bend. When I use the basic hair particles they do, so I assumed this is because my objects do not have segment that can be used for bending in the particle system but I did'nt find anything explaining what I need to do to achieve that.
I assume thats why the vortex force field is acting so stange because in my mind (and in nature) I don't think they'll do that (see video)
Here some screenshot for demonstrate
the vortex force field
The particle system
and finally a render of the effect https://youtu.be/PHE01EY38rU (sorry for the size and quality but it make foreverrrr to even do that on my computer but I think thats enough to show what I mean)