Interface evolution of a liquid Taylor droplet during passage through a sudden contraction in a rectangular channel

Abstract

A lattice Boltzmann discretization based numerical study has been carried out to study the effect of sudden contraction in a rectangular channel during uprise of a lighter liquid species inside a heavier one. Diffused interface concept has been adopted for the prediction of liquid-liquid interface. Simulations are performed for passage of a kerosene droplet through restrictions like a sudden contraction, orifice, and remotely spaced contraction-expansion. A wide range of contraction ratio, droplet volume, and channel inclinations are considered to study the evolution of interface along the rectangular conduit. Symmetric change of interfacial shape has been observed while droplet tries to accommodate in the narrow confined zone after contraction. Using streamlines and velocity vectors, the reasons behind the interfacial evolution are established. With a decrease in contraction ratio, resistance against droplet passage increases this produces lengthier lamella like kerosene interface in the downstream of contraction. Droplet volume showed a significant effect in constructing the tail interfacial structure, which allows water to penetrate inside kerosene core for larger volumes. During the passage of a kerosene droplet in a channel with different inclination, stage of an asymmetric interface is observed. By providing offset contraction, local asymmetries are observed in the kerosene interface near the plane of area reduction. Efforts are continued to observe the kerosene droplet passage through an orifice which showed restricted and free interfacial evolution after contraction and expansion sections, respectively. The stabilizing zone between contraction and expansion showed influence on the generation of daughter droplets by fragmenting kerosene interface.