Hydrodynamics of bubble coalescence in microchannels. (13th December 2020)

• Record Type: Journal Article
• Authors: Khadiya, Siddharth; Kumari, Sadhana; Gupta, Raghvendra
• Is Part Of: Canadian journal of chemical engineering. Volume 99:Number 5(2021)
• Page Start: 1199
• Page End: 1210
• Publication Date: 2020-12-13
• Subjects: bubble coalescence -- microfluidics -- moving domain -- Taylor bubble -- VOF; Chemical engineering -- Periodicals; Technology -- Periodicals; 660.05
• DOI: 10.1002/cjce.23918
• Languages: English
• ISSNs: 0008-4034

Abstract

Abstract: Gas‐liquid flow in microchannels is relevant to a number of microfluidic devices without moving parts for application in chemical micro‐processing, inkjet printing, and electronics cooling. Over a large range of gas and liquid flow rates, gas bubbles have the same size as that of the channel. Such bubbles are nearly spherical in shape until their radius is less than that of the channel. The bubbles with a larger volume expand along the axis taking a capsular or bullet shape and are commonly known as Taylor bubbles. For air‐water flow, the spherical bubble is observed to move with a velocity higher than that of the Taylor bubble. In this work, the flow of a Taylor bubble followed by a spherical one, initially separated by several channel diameters, has been studied numerically using the volume of fluid (VOF) method. The hydrodynamics during the bubble approach as well as the evolution of the doublet, that is, the merged bubble, has been investigated. To track the velocity of each bubble with time during the bubble approach stage, a novel methodology has been developed using k‐means clustering algorithm. The evolution of the interface of the doublet has been monitored. The neck radius of the doublet grows as τ 0.5, τ being the time since the contact between the bubble interfaces, when the interface is away from the wall. In the near wall region, the radius grows more slowly and is proportional to τ 0.1 .