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Article Dans Une Revue Canadian Journal of Chemical Engineering Année : 2011

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

Résumé

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 et versions

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

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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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