Motion of a small bubble in forced vibrating sessile drop

摘要

In this letter,the motion of small gas bubbles within sessile water drops on a vibrating substrate is investigatednumerically using a two-phase diffuse interface method.Depending on the amplitude of the plate vibration,themotion of the gas bubbles falls into three distinct regimes:oscillating within the drop,sticking to the substrate,orescaping from the drop.In particular,the motion of oscillating bubbles follows a harmonic function,and is foundto be closely related to a combined effect of the deformation of the sessile drop and the vibration of the plate.Tointerpret the underlying mechanism,we analyze the dominant forces acting on the bubbles in the non-inertialframework fixed to the plate,and take account of the periodic deformation of the drop,which effectively inducesflow acceleration inside the drop.As a result,we establish a theoretical model to predict the bubble motion,andcorrelate the amplitude and phase difference of the bubble with the Bond and Strouhal numbers.The theoreticalprediction agrees with our numerical results.These findings and theoretical analysis provide new insights intocontrolling bubble motion in sessile drops.