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Journal Articles Canadian Journal of Chemical Engineering Year : 2011

Influence of bubbles characteristics on the skin friction and velocity gradient on solid sphere

Abstract

A detailed study of the effects of individual bubbles at high gas flow-rate has shown, that the dominant influence on skin friction over a solid sphere is the bubble volume in compared to bubble frequency. Nevertheless the bubble frequency is very important in case of low gas flow-rate. Referring to bubbles produced by a gas distributor, statistical and spectral analyses were performed to study the influence of bubbling on exposure time and magnitude of fluctuations. Referring to a calibrated bubble train, the existence of critical frequency is demonstrated. A bubble with larger volume and a mobile, oscillatory surface generates larger velocity gradient. In the case of gas distribution, histograms of the velocity gradient for a 2 mm glass sphere creating bubble coalescence reveal the maximum exceeds 48 000 s−1 in the front zone and 2000 s−1 in the rear zone (θ = 180°). For 5 mm plastic spheres creating bubble break-up, the maximum of the velocity gradient is only 8100 s−1 for the front part of the sphere and 2000 s−1 in the rear zone.
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Dates and versions

hal-03469346 , version 1 (07-12-2021)

Identifiers

Cite

Abdel Hafid Essadki, Iordan Nikov, Henri Delmas. Influence of bubbles characteristics on the skin friction and velocity gradient on solid sphere. Canadian Journal of Chemical Engineering, 2011, 89 (6), pp.1358-1365. ⟨10.1002/CJCE.20647⟩. ⟨hal-03469346⟩
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