Two-dimensional simulation of liquid metal spray deposition onto a complexsurface: II. Splashing and redeposition

A two-dimensional model (Djuric Z, Newbery P and Grant P 1999 Modelling Sim ul. Mater. Sci. Eng. 7 553) of liquid metal spray deposition on an arbitrar y surface has been extended to include the important processes of splashing of spray droplets during collision with the surface, and the subsequent re deposition of scattered material. Every point on the surface has been treat ed as both a receiver and an emitter of sprayed material. The action of the se micro sources has been modelled by several assumed micro source function s of the spatial distribution of splashed material. The moving surface has been traced by following the trajectories of its points as spraying proceed s. These trajectories were calculated in a way similar to that used previou sly (Djuric Z, Newbery P and Grant P 1999 Modelling Simul. Mater: Sci. Eng. 7 553), except that they now can, in principle, intersect each other. To a chieve a physically reasonable solution, a new algorithm has been developed to resolve this problem. The model has been applied in several cases and the simulations compared wi th experimental results. By including or excluding droplet splashing effect s, it has been possible to analyse the importance of redeposition both in s imulations and experiments. In the case of splashing, different assumed mic ro source functions resulted in slightly different but geometrically simila r predicted shapes. The modelling of these functions was based on the conce pt of the continuity of splashing and re-emission processes, a simplicity o f the point source, a qualitative analysis of splashing events observed in experiments by high-speed imaging, the total mass preservation constraint, and some theoretical and experimental results of a single droplet impact on to a hard surface. Using these results, it was possible to predict where di rect spraying dominated deposit growth, and where the subsequent redepositi on had a major influence on deposit growth and the final shape. While in so me cases model predictions are in reasonable agreement with available exper imental data, the limitation of the model in accurately describing three-di mensional effects during droplet splashing has been revealed.