Heat transfer and fluid dynamics during the collision of a liquid droplet on a substrate - I. Modeling

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.