Capillarity-induced resonance of blobs in a 3-D duct: lattice Boltzmann modelling

The present study deals with the analysis of capillarity–wettability interaction of the trapped nonwetting phase. The displacement of a three-dimensional immiscible blob subject to oscillatory acoustic excitation in a duct is explored using the lattice Boltzmann method. The effect of the width of the channel, amplitude of the force, wettability, viscosity and frequency on blob dynamics are investigated. The response of the blob with pinned contact line shows underdamped behavior whereas with that of sliding contact line exhibits overdamped character. It is observed that increasing the amplitude of the force increases the mean displacement and frequency response. The displacement of the blob reveals underdamped character for lesser viscosity and overdamped character for higher viscosity. It is found that the mean displacement of the blob is greater for uniform wettability as compared to mixed wettability surface for the pinned configuration. The surface with strong hydrophobic and hydrophilic nature shows more displacement. The resonance behavior of the blob on the surface with different wettabilities is discussed. It can be inferred that at resonating frequency blob show maximum displacement. The effect of wettability is not so prominent at high capillary numbers. However at low capillary number the wettability is crucial in mobilization of trapped blob.