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Wall Shear Stress Induced by a Large Bubble Rising in an Inclined Rectangular Channel
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SYSNO ASEP 0431846 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Wall Shear Stress Induced by a Large Bubble Rising in an Inclined Rectangular Channel Author(s) Tihon, Jaroslav (UCHP-M) RID, ORCID, SAI
Pěnkavová, Věra (UCHP-M) RID, ORCID, SAI
Vejražka, Jiří (UCHP-M) RID, ORCID, SAISource Title International Journal of Multiphase Flow. - : Elsevier - ISSN 0301-9322
Roč. 67, DEC (2014), s. 76-87Number of pages 12 s. Language eng - English Country GB - United Kingdom Keywords taylor bubble ; bubble rise velocity ; bubble shape Subject RIV CI - Industrial Chemistry, Chemical Engineering R&D Projects GAP101/12/0585 GA ČR - Czech Science Foundation (CSF) Institutional support UCHP-M - RVO:67985858 UT WOS 000345475700007 DOI 10.1016/j.ijmultiphaseflow.2014.07.005 Annotation The rise of single air bubbles in inclined rectangular channels was experimentally investigated. Two-segment electrodiffusion probes were used to measure wall shear rate profiles along the passing bubbles. They provided information on reverse flow in a liquid film separating the bubble from the wall, capillary waves appearing at the bubble tail, and near-wall flow fluctuations in the bubble wake. The corresponding bubble shapes and rise velocities were obtained from simultaneous visual observations done by a high-speed camera. The experiments were carried out for three channel depths (1.5, 4, and 8 mm), various channel inclinations (from 5° to 90°), bubble volumes (from 1 to 80 ml), and liquid up-flow velocities (from 0 to 0.2 m/s). In vertical channels, the wall shear rate trace of a bubble rise is primarily influenced by the channel depth. As the frontal shape of large bubbles does not change with the bubble size, also the wall shear rate measured under these bubbles evolves in the same manner. In inclined channels, the liquid film is unequally distributed above and under the bubble with the maximum reverse flow observed under the bubble at middle inclinations. Laminar liquid co-flow makes the liquid film around the bubble thicker and in inclined channels slightly pushes the bubble toward the center-line position. The bubble velocity scaling based on the channel perimeter is confirmed to be suitable for vertical channels with stagnant liquid. The linear relationship between the bubble rise and liquid mean velocity is identified under co-flowing conditions at all channel inclinations. Workplace Institute of Chemical Process Fundamentals Contact Eva Jirsová, jirsova@icpf.cas.cz, Tel.: 220 390 227 Year of Publishing 2015
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