Summary (I): This paper presents a numerical study of the fluid dynamics and heat transfer phenomena during the impingement of a liquid droplet upon a substrate. The theoretical model, based on the Lagrangian formulation, is solved numerically utilizing the finite element method. A deforming mesh is utilized to simulate accurately the large deformations, as well as the domain nonuniformity characteristic of the spreading process. The occurrence of droplet recoiling and mass accumulation around the splat periphery are standout features of the numerical simulations and yield a nonmonotonic dependence of the maximum splat radius on time. The temperature fields developing in both the liquid droplet and the substrate during the impingement process are also determined. To this end, liquid metal and water droplet collisions on different substrates were investigated. Convection effects on the temperature field development were found to be important for the entire history of spreading. These effects resulted sometimes in a practically radial temperature variation at late stages of spreading, particularly so in the cases of high impact velocities.
Summary (II): This paper presents an experimental study of liquid droplet impingement upon a substrate. Qualitative as well as quantitative comparisons were conducted between the experimental measurements and the numerical predictions from the theoretical model in part I of this paper. The droplet deformation process was visualized using a two-reference-beam pulse holography method. Measurements of the transient splat radius were performed with a novel photoelectric technique. The experimentally obtained droplet shapes were similar to the numerically predicted ones for the same conditions. The impact dynamics was characterized by droplet spreading, recoiling and oscillations. The spreading and recoiling motions depended upon the initial velocity as well as the droplet properties. In summary, the theoretical predictions agreed well with the experimental results until the late stages of the droplet spreading process.