Hello all,

I'm using Fluent for simulation of a droplet-particle impact problem. Droplet velocity is 0.7 m/s and particle moves in opposite direction with 7 m/s to make a head-on collision (I'm using VOF with dynamic mesh).

Based on my experimental results, after impact, droplet starts forming a liquid film and departs from the particle. However, in simulations it seems that this thin liquid film is only formed if I activate the 'dynamic gradient refinement'. Otherwise, if I use even a very fine grid but without dynamic refinement, the liquid is not separated from the surface and passes around the particle (please see the attached picture).

Note that the only difference between these two simulations is using dyn. refinement. Another observation is that when dyn. ref. is activated, there is a very tiny air gap between liquid ad particle surface (which does not seem to be reasonable-shown in case#2), but in case#3, the liquid is in contact with surface which makes sense, but the desirable liquid film does not form.

Any idea about the reason?

Thanks,

PS. I set dyn. ref. to reduce the mesh size based on the 'phase gradient'. Therefore, the mesh starts becoming finer as it approaches the interface.