VOF-DPM particle bounce
I built VOF-DPM model of rotatory flow with particle sedimentation. VOF part gives me very good results, but I have a problem with DPM part of the model. For some reason particles bounce off the wall and escape fluid, I attached picture with particle tracks. Particle time is correct, but their location is outside the fluid (green isosurface VOF=0.5).
I tried with and without interaction with continuous phase at DPM window; with and without virtual mass force, pressure gradient force and even two-way turbulence coupling (it's not suitable) and physical models - those were in various combinations. I set wall DPM reflection coefficients parameters as Normal/ Tangent as 0.3/1; 0.3/0; 0/0 and left blank polynominal. I also tried DEM collision model and collision partner has same value configurations. With DEM convergence was not so good and it is not necessary. I found that DPM is more suitable for solid particles and DEM is better for droplets.
In solution methods, I tried pressure-velocity coupling simple and coupled. I always use Second order upwind for discretization.
Is there something I'm missing? My domain is filled with air initially, and the mixture of fluid and particles enters the domain, why particle still bounce off the fluid?
I would be very grateful for any suggestion.