Numerical study of natural oscillations of supported drops with free and pinned contact lines

The oscillation of droplets supported by solid surfaces is important for a wide variety applications such as dropwise condensation. In the present study, axisymmetric natural oscillations liquid drop flat surface are investigated direct numerical simulation. liquid–gas interface captured using geometric volume-of-fluid method. A parametric study carried out varying equilibrium contact angle and gravitational Bond number (Bo). Both positive negative gravities considered, thus results cover both pendant sessile drops. To incorporate effect line mobility, two asymptotic limits, namely, pinned (PCL) free (FCL) conditions, considered their effects on features characterized. predicted frequencies PCL FCL serve upper lower bounds general situations. initiated increasing gravity magnitude short time. first mode due to centroid translation dominates excited oscillation. frequency scales with capillary frequency, normalized monotonically decreases angle. For zero gravity, computed all angles agree remarkably well inviscid theory conditions. kinetic energy correction factor introduced account additional contribution oscillation-induced internal flow overall drop. increase Bo, decrease angle, when condition changed from PCL. variation change Bo particularly significant large, suggesting that must be incorporated accurately predict drops hydrophobic or superhydrophobic surfaces.