Capillary-scale solid rebounds: experiments, modelling and simulations

Abstract

A millimetre-size superhydrophobic sphere impacting on the free surface of a quiescent bath can be propelled back into the air by capillary effects and dynamic fluid forces, whilst transferring part of its energy to the fluid. We report the findings of a thorough investigation of this phenomenon, involving different approaches. Over the range from minimum impact velocities required to produce rebounds to impact velocities that cause the sinking of the solid sphere, we focus on the dependence of the coefficient of restitution, contact time and maximum surface deflection on the different physical parameters of the problem. Experiments, simulations and asymptotic analysis reveal trends in the rebound metrics, uncover new phenomena at both ends of the Weber number spectrum, and collapse the data. Direct numerical simulations using a pseudo-solid sphere successfully reproduce experimental data whilst also providing insight into flow quantities that are challenging to determine from experiments. A model based on matching the motion of a perfectly hydrophobic impactor to a linearised fluid free surface is validated against direct numerical simulations and used in the low Weber number regime. The hierarchical and cross-validated models in this study allow us to explore the entirety of our target parameter space within a challenging multi-scale system.

31 pages, 16 figures

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Cited by in corpus (9)

• Drop impact on viscous liquid films
• Inertio-capillary rebound of a droplet impacting a fluid bath
• Drag on a partially immersed sphere at the capillary scale
• Drop rebound at low Weber number
• Similarity solutions in elastohydrodynamic bouncing
• Theoretical modeling of capillary surfer interactions on a vibrating fluid bath
• Impact of a rigid sphere onto an elastic membrane
• Droplet rebounds off a fluid bath at low Weber numbers
• Rheology of Two-Dimensional Dilute Emulsions