Cloud structuring of microbubbles ascending along a vertical wall. (23rd November 2019)

• Record Type: Journal Article
• Authors: Watamura, Tomoaki; Kitagawa, Atsuhide; Murai, Yuichi
• Is Part Of: Chemical engineering science. Volume 208(2019)
• Publication Date: 2019-11-23
• Subjects: Fluid dynamics -- Bubbly flow -- Ultrasonic velocity profiling -- Flow visualization; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2019.07.050
• Languages: English
• ISSNs: 0009-2509

Abstract

Graphical abstract: Highlights: We visualized fluid motions driven by a vast number of microbubbles. Microbubble-clouds exhibit three-dimensional and spatially periodic patterns. Coalescence of microbubble-clouds caused by the hydrodynamic interaction. Motion of bodies in fluids models the unsteady motion of microbubble-clouds. Abstract: To elucidate the motion of spatiotemporally developing flow structures driven by densely concentrated microbubbles, we experimentally investigated the distribution and motion of microbubbles rising along a vertical plane wall. We performed optical measurements and an ultrasonic velocity profiling to determine the distribution and motion of microbubbles. We found that the microbubbles form clouds (fluid blobs containing rich microbubbles) with a three-dimensional structure, the spatial patterns of which become more periodic in the streamwise direction than in the spanwise direction. In addition, owing to the coalescence of neighboring microbubble clouds caused by the hydrodynamic interaction between them, the separation length of the buoyant force distribution of microbubbles increases with increasing the distance from the bottom of the tank. According to the Reynolds number of the microbubbles cloud presented here, we conclude that the unsteady motion of microbubble clouds can be analogously modeled as an interacting motion of moving bodies in flow.