Drop impact onto a moving substrate: Aerodynamic rebound

The dynamics of droplets approaching fast moving surfaces of high surface-tangential velocities is relevant to numerous technical applications, such as icing phenomena in aviation. Due to the substrate motion a boundary layer is formed which interacts with impacting droplets. In the present study, the transition from drop impact and splashing to boundary layer induced drop rebound is investigated for varying drop diameters, drop and plate velocity, as well as impact angles. It is found that this transition is strongly influenced by the degree of drop deformation that is induced by aerodynamic forces acting on the drop when it enters the boundary layer. Based on these considerations, a threshold model is obtained that describes the transition from splash to aerodynamic rebound. It is shown that the model is valid for a laminar and a turbulent boundary layer agreeing well with own and existing experimental data.