Simulation of liquid-jet overflow in droplet deposition processes

Porosity formation in spray deposition processes is investigated. The emphasis is on one possible mechanism of micro-pore formation during droplet spreading and solidification: liquid-jet overflow. To this end, the Navier-Stokes equations are solved numerically using finite differences and the free surface is tracked using the Volume of Fluid (VOF) method. A previously developed multi-directional solidification algorithm is adapted and implemented in the Navier-Stokes solver to perform numerical simulations of liquid-metal droplet impact, spreading, and solidification. The results obtained allow a detailed description of the liquid-jet overflow mechanism and of the resulting solidified disk morphology. The influence of the Weber and Reynolds numbers, the solidification constant, and the contact angle are investigated. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.