Reducing the contact time of impinging droplets on non-wetting surfaces
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This work examines the use of macro-textured surfaces to reduce the contact time between impinging liquid droplets and non-wetting surfaces. Six macro-texture geometries are evaluated for their impact on maximum deformation diameters and contact time. The geometries considered are a set of spokes extending radially out from the impact point. Spoke counts of n=1 to n=6 are evaluated. The six spoke geometry demonstrated the maximum reduction in contact time with a 49% measured contact time reduction compared to a flat plate. This study evaluates droplet impacts experimentally using high-speed video. Samples are traditionally machined aluminum surfaces made non-wetting though the use of the Leidenfrost effect. In conjunction with the experimental results, we develop an analytical model to predict the contact time reduction based solely on impact Weber number and texture geometry. Finally, this study considers the impact of the macro-texture geometries on the dispersion of daughter droplets. High spoke-count geometries were observed to produce more than one droplet per spoke. Here again we develop an analytical model to predict this phase doubling based on a quasi-steady-state Rayleigh Plateau instability approach.