Dynamics of spherical particle impact on wall and effects of surface roughness

Direct numerical simulations (DNS) of particle impact on wall are carried by Immersed boundary (IB) method. Present research work discusses the particle-wall collision for a range of Stokes (St) numbers such that flow varies between highly viscous to inertial regimes. We investigate and validate that for St < 10, particle does not rebound whereas at St > 500, particle-wall collision asymptotes to the dry collision defined by coefficient of restitution. The velocity before rebound has parabolic profile whereas after rebounding it varies non-linearly with time. Two levels of mesh hierarchy are used where particle resides at finest level of mesh hierarchy which resolves the near wall interactions effectively, along with lesser computational time. We also study the effects of surface roughness on impact dynamics. Particle trajectory and velocity profiles are compared with and without the effect of wall roughness. Further the change in rebound characteristics in presence of two particles falling side by side on the wall is investigated.