Bouncing dynamics of spheroidal drops on macro-ridge structure

Bouncing drops on solid surfaces have gained increasing attention for various practical applications, such as self-cleaning and anti-icing strategies. Breaking the circular symmetry in bouncing dynamics on a ridge enables drop dynamics to be modified significantly and the residence time of drops on surfaces to be reduced. Here, we numerically investigate the asymmetric bouncing dynamics of oblate and prolate spheroidal drops on a superhydrophobic surface decorated with a rectangular ridge to demonstrate the feasibility of further reducing the residence time by shaping raindrop-like drops. The residence time is investigated for various aspect ratios and Weber numbers, which are discussed based on impact stages of spreading, splitting, and retraction. The underlying principle behind the residence time reduction is analyzed by quantifying the temporal variations in the widths and the axial momenta of the drops. The bouncing directions of the spheroidal drops are closely related to the momentum distributions during the retraction. We investigate how to change the residence time for ridges of different heights and widths. The symmetry-breaking bouncing of the spheroidal drops on ridge surfaces will provide fundamental and practical inspiration for the efficient control of drop mobility.