Simulation of Fluid Flow and Heat Transfer Including Phase Change During the Impact of Semi-Molten Particles

A numerical method is proposed in this paper which is capable of modeling the impact and deposition of semi-molten particles. By attributing a high viscosity to the solid region, simulating the motion of solid cores including solidification/melting is made possible inside the particle. The Navier-Stokes equations are solved in combination with the Volume-of-Fluid (VOF) technique to track the free surface of the particles. In addition, the heat transfer including phase change is modeled using the enthalpy method. The viscous terms are treated implicitly to relax the restrictions associated with small computational time-steps in explicit formulations. Several case studies with operating conditions of a typical thermal spray process are simulated. These cases include the impact of molten and semi-molten nickel particles in an atmospheric plasma spray process (APS). The effects of various parameters such as particle solid-core diameter, initial velocity and temperature are investigated. The simulations show that the size of the solid core has an important effect on the amount of particle splashing during the impact.