Dynamic characteristics of droplet coalescence-induced jumping on bioinspired symmetric rhombic microstructured surfaces

The coalescence-induced droplet jumping phenomenon holds significant engineering potential in applications such as self-cleaning, anti-icing/frosting, and enhanced condensation heat transfer. Using a three-dimensional lattice Boltzmann method (LBM), this study numerically simulates droplet coalescence and jumping behaviors on bioinspired symmetric rhombic microstructured surfaces (BSRMS), with particular focus on the effects of droplet radius ratio and micropillar geometry on the jumping dynamics and energy conversion. The results reveal that increasing the central ridge height markedly enhances both the maximum jumping and energy conversion efficiency of jumping droplets, with the latter reaching up to 29.38% when the radius of both droplets is 20lu and the height of the middle ridge is 19lu. For two mismatched droplets, a horizontal velocity component emerges, causing the droplet to deviate from its original position, and the maximum horizontal velocity increases with the central ridge height. Importantly, jumping behavior exhibits well-defined critical conditions: no jumping occurs when the radius ratio is below 0.5 or the energy conversion efficiency is below 2%. Within a specific parameter range (radius ratio ϕ=0.75∼1, central ridge height H = 5∼15lu; ϕ=0.625, H = 7∼11lu), the energy conversion efficiency shows an approximately linear dependence on the radius ratio, and the slope of this linear relationship grows with increasing central ridge height.