Oblique impact dynamics of micron particles onto a liquid surface

Micron particles rotate and their trajectories deviate from the impact direction when impacting the liquid surface obliquely; thus their impact dynamics is largely different from that of vertical impact, which remains to be studied in depth. In this study we established a three-dimensional simulation method by solving the coupled equations of particle motion and fluid flow and adopting a dynamic meshing technique and slip velocity boundary condition that accurately reproduced the particle motion and gas-liquid interface evolution during oblique impact. Our results, based on detailed flow field and acting forces and moments analyses, demonstrate that the particle's nonaxisymmetric wetting leads to the nonaxisymmetric distribution of fluid pressure and shear stress along the particle surface, and thus deviates the dominating forces at different impact stage from its direction of motion, which makes the particle trajectory deviate from the impact direction and also generates a viscous moment that rotates the particle. We also illustrate how the impact angle and Weber number modulate the flow field around the particle as well as the acting forces and finally influence the particle motions. These findings provide a deep understanding of the dynamics of the nonaxisymmetric impact of the micron particle on liquid surfaces, which is a ubiquitous scenery in nature and industry.