A model to predict the oscillation frequency for drops pinned on a vertical planar surface

Accurate prediction of the natural frequency for the lateral oscillation of a liquid drop pinned on a vertical planar surface is important to many drop applications. The natural oscillation frequency, normalized by the capillary frequency, is mainly a function of the equilibrium contact angle and the Bond number (Bo), when the contact lines remain pinned. Parametric numerical and experimental studies have been performed to establish a comprehensive understanding of the oscillation dynamics. An inviscid model has been developed to predict the oscillation frequency for wide ranges of Bo and the contact angle. The model reveals the scaling relation between the normalized frequency and Bo, which is validated by the numerical simulation results. For a given equilibrium contact angle, the lateral oscillation frequency decreases with Bo, implying that resonance frequencies will be magnified if the drop oscillations occur in a reduced gravity environment.

Automated summary

This study reveals the relationship between the natural frequency of lateral oscillation of a liquid drop pinned on a vertical surface, equilibrium contact angle, and Bond number. As the Bond number increases, the lateral oscillation frequency decreases, suggesting that resonance frequencies are amplified in reduced gravity environments.