A 2D Model of Semi-molten Drop Impact for Thermal Spray Application
Tommy Che-Ming Wu
Graduate Department of Materials Science and Engineering, University of Toronto
Abstract
In thermal spraying, semi-molten (or partially-melted) particles are likely to form when the sprayed particles are insufficiently heated, or when a composite material is deposited. The present 2D model serves to begin to assess the spreading behavior of a semi-molten particle when impacting a solid substrate. An Immersed-Boundary (IB) scheme was implemented in an axisymmetric fluid model to simulate fluid flow in the presence of a solid core. The IB method calculates a forcing term, which is add...Moreed to the momentum equation, to enforce the no-slip boundary condition at the core surface. Results are presented for the impact of a semi-molten tin droplet of radius R for a wide range of solid core radii r, varying the drop size ratio r/R, and the impact velocity Uo. To take into account the fluidity of a semi-molten drop, a modified maximum spread degree, * max, is defined. The maximum spread degree * max is found to decrease significantly when the solid core size r is comparable to the drop size R. As the solid core size increases, one significant change in fluid behavior during spreading is that the rate of energy dissipation of inertia to viscous forces and surface tension increases, which causes fluid to recoil at an earlier time than a completely molten tin drop.
keywords:Drop Impact; semi-molten tin
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