Dynamic behavior of droplets impacting on wetted cylindrical surfaces

Dynamics of droplets impact on wetted horizontal cylinders were investigated using both experimental and theoretical approaches. Temporal variations of droplet height and film thickness on the impact center were measured. Experimental results indicate three distinct phases, namely the initial droplet deformation phase, the inertia dominated phase, and the viscosity dominated phase. The effects of liquid type, impact velocity, and target-to-droplet size ratio (D*) on the film thickness have been studied. The temporal variation of nondimensional film thickness during the first two phases collapses onto a single curve for different D* and impact velocities, and a new expression was proposed based on this fact. A theoretical model for the film flow in the vicosity dominated phase has been established. A quantitative analysis was further conducted on the gravity driven creeping flow. Based on the theoretical results and experimental data, an empirical expression for film thickness was proposed. Both the theoretical model and the empirical expression show strong agreement with the experimental results.