78th Annual Meeting of the APS Division of Fluid Dynamics (Nov 23 — 25, 2025)
P040: Vapour Shielding
We investigate the collective evaporation dynamics of water droplets arranged on a heated substrate. When droplets evaporate in close proximity, vapour accumulation in the surrounding region suppresses local evaporation. Since vapour diffusion is slower than evaporation, this accumulation forms a shielding effect that reduces evaporation at droplet interfaces facing neighbouring droplets. The resulting suppression induces asymmetric cooling (creates thermal Marangoni flow) at the corner droplets, leading to symmetry breaking and azimuthal flow, while the central droplet remains more symmetric due to uniform suppression. Direct numerical simulations using a phase-field model of a five-droplet array clearly show the vapour shielding effect and predict symmetry breaking in the corner droplets.
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