Energy Conversion Characteristics of Coalescence-Induced Jumping of Translating and Rolling Nanodroplets on Superhydrophobic Surfaces

Coalescence-induced droplet jumping is a key mechanism for passive phase-change transport and energy-efficient liquid removal on superhydrophobic surfaces. While static droplet coalescence has been widely studied, the energy conversion behavior of moving droplets, especially under rolling motion, remains unclear at the nanoscale. In this work, molecular dynamics simulations are conducted to investigate the coalescence-induced jumping of translating and rolling nanodroplets over a range of Weber numbers. Results show that translational motion mainly compresses the coalescence timescale, while the dimensionless jumping velocity remains nearly constant due to the interfacial energy constraint on vertical kinetic energy. In contrast, rolling motion enhances vertical momentum establishment and modifies directional energy partitioning. Although the absolute vertical kinetic energy increases under rolling conditions, its conversion efficiency decreases with increasing initial velocity, while horizontal and total energy conversion efficiencies exhibit a rise-then-decline trend, indicating an optimal inertial regime. These findings elucidate how motion mode governs energy redistribution during droplet coalescence and provide nanoscale insight for improving energy-efficient phase-change transport.