Numerical simulation of droplet behavior on an inclined plate using the Moving Particle Semi-implicit method

This paper presents the numerical simulation methods used to reproduce droplet retention and sliding on an inclined surface by using the Moving Particle Semi-implicit (MPS) method. The MPS method is useful for simulating free surface flows with highly deformed gas-liquid interfaces, such as the behavior of condensed water in an evaporator. However, the existing MPS method cannot correctly reproduce the behavior of a droplet retention and droplet sliding on an inclined surface. In the simulation of a droplet on a wall using the existing MPS method, the simulated droplet starts sliding as soon as the wall is inclined even slightly and falls down at a very high speed. In this study, the details of the forces acting from the wall to a droplet are considered, and the boundary condition models that contain the resistance forces acting on the contact line of a droplet are proposed. Droplet retention and droplet sliding on an inclined plate are successfully simulated by using the proposed models. Furthermore, the simulation results are compared with the experimental results reported in literature. The relationship between the droplet volume and critical sliding angle and that between the inclination angle of a slope and droplet sliding velocity are each compared using the experimental results and evaluated both qualitatively and quantitatively; they show good agreement with the experimental results.