Transport phenomena during the impingement of liquid metal droplets on a substrate.

摘要

This thesis presents a study of the fluid dynamics and heat transfer phenomena during a molten metal droplet impingement upon a substrate. The work is both theoretical and experimental. The theoretical study accounts for the presence of surface tension and the heat transfer during the spreading process. The theoretical model is formulated using the Lagrangian specification and solved numerically utilizing the finite element method with a deforming mesh to simulate accurately the large deformations, as well as the domain nonuniformities characteristic of the spreading process. The experimental investigation of the droplet impact dynamics is accomplished with a two-reference-beam holography method for the visualization of the droplet deformation process and with a novel photoelectric technique, for the fast recording of the droplet spreading and recoiling history upon impact on the substrate.;A novel non-intrusive droplet spreading measurement technique based on optical photo-detection is documented. The theoretical predictions agreed well with the experimental results for the droplet spreading process.;The results document the effects of impact velocity, droplet diameter, surface tension, and material properties on the fluid dynamics of the deforming droplet. The results also document the temperature fields developed within the droplet and the substrate. The effects of droplet impact velocity, Prandtl number, and droplet size on the cooling of a molten metal droplet as well as a water droplet impacting on a host of substrates are documented in this thesis.