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Droplet retention on an incline. (English) Zbl 1262.76033

Summary: The present study seeks to understand and predict droplet retention on smooth hydrophobic surfaces. The droplet shape and the advancing and receding contact angles are experimentally measured as a function of droplet size under the action of a gravitational force at different inclination angles. The advancing and receding contact angles are correlated with static contact angle and Bond number. A Volume of Fluid-Continuous Surface Force model with varying contact angles along the triple contact line is developed to predict droplet shape. The model is first verified against a two dimensional analytical solution. It is then used to simulate the shape of a sessile droplet on an incline at various angles of inclination and to determine the critical angle of inclination as a function of droplet size. Good agreement is found between experimental measurements and predictions. The contact line profile and contact area are also predicted. The contact area predictions based on a spherical-cap assumption are compared to the numerical predictions and are found to underpredict the droplet contact area.

MSC:

76D45 Capillarity (surface tension) for incompressible viscous fluids
76D05 Navier-Stokes equations for incompressible viscous fluids