Understanding of Fluidic Physics during Bypass of a Taylor Bubble around a Transverse Insert in a Viscous Medium

Abstract

Fluidic physics during bypass of a Taylor bubble around a transverse insert is experimentally observed in a viscous liquid medium. Unified and fragmented bypasses are identified depending on the length scale of the insert. Sequential stages of these mechanisms are elaborated on from the kinematics of the bubble. Prediction of the bypass and pinch-off time scale validates the required diameter ratio between the insert and tube for a transition. Using photographic analysis, phenomena like air-jet plunging, neck recovery, and shape transformation of daughter bubbles are discussed for the bypass and pinch-off systems. The 2D collapse of the gas stem at the initial stage and the volumetric pinch-off in the later stages have been conceptualized. The stability of the bubble train in pinch-off systems is evaluated, and coalescing/noncoalescing trains are identified by predicting the wake length. A pressure-jump model has been proposed to identify the reason for bubble-unified bypass and pinch-off.