Reducing the contact time of off-center impacts

Abstract

When a droplet off-center impacts a macro-ridge, the contact time increases with off-center distance ( Δ x * ), which are closely related to two mechanisms, i.e., the redistribution of liquid volume and the asymmetry of the liquid film. Therefore, changing the asymmetry of the liquid film may provide fundamental inspiration for the efficient control of the contact time. Using lattice Boltzmann method simulations, the dynamics of a droplet off-center impacting a ridge on a superhydrophobic surface are explored to demonstrate the feasibility of reducing contact time by changing the asymmetry of the liquid film, which is changed by manipulating the inclination of the ridge. For positive off-center impact ( Δ x * > 0 ), the contact time decreases with the increase in the inclined angle as increasing the inclination can decrease the asymmetry of the liquid film. For negative off-center impact ( Δ x * < 0 ), tilting the ridge can further reduce the asymmetry of the liquid film to a limit, and its influence can be ignored at θ i = 30 ° – 60 °, leading to the contact time decreasing more significantly compared with that for Δ x * > 0. On this basis, a quantitative relationship of contact time for a droplet off-center impacting an inclined ridge is established. This work provides fundamental and practical inspiration for the efficient reduction of contact time for off-center impacts.