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Study of bubbles entrapped into a gas-sheared liquid film

Hann, David B.; Cherdantsev, Andrey V.; Azzopardi, Barry J.


Associate Professor

Andrey V. Cherdantsev

Barry J. Azzopardi


The surface of a thick liquid film under strong gas shear is covered by large-scale disturbance waves and small-scale ripples. Disruption of these ripples on top of disturbance waves by the gas stream leads to the creation of droplets that are entrained into the gas core and may deposit back onto the film surface. In addition, gas may be entrapped by the liquid film in the form of bubbles of various sizes. In this work, the study of gas bubble creation was performed in a horizontal rectangular duct using the brightness- based laser-induced fluorescence technique. With this technique, the instantaneous height of the liquid film was measured with a 40 ?m spatial resolution over a 51 mm by 20 mm area at speeds of 10 kHz. The entrapped bubbles and entrained/depositing droplets are detectable in the data and can thus be studied simultaneously with the waves on the film surface. Several scenarios of bubble entrapment and collapse were identified and discussed. The dynamics of entrapped bubbles was studied quantitatively using an automatic processing algorithm, confirming and elucidating the results of qualitative observations. The effect of the flow parameters on the bubbles concentration, velocity and size distributions was studied separately for the bubbles inside the disturbance waves and inside the thin base film between the dis- turbance waves. It was shown that the bubbles are mostly created due to oblique impacts of droplets at the base film and are accumulated by the disturbance waves. A small number of bubbles of larger size are created in front of disturbance waves and remain inside the disturbance waves. The velocity of the bubbles is affected by the velocity of the surrounding liquid. Using the bubbles as tracers, a profile of longitudinal liquid velocity was constructed and a noticeable increase of wall shear under the rear slopes of disturbance waves was found.


Hann, D. B., Cherdantsev, A. V., & Azzopardi, B. J. (2018). Study of bubbles entrapped into a gas-sheared liquid film. International Journal of Multiphase Flow, 108, 181-201.

Journal Article Type Article
Acceptance Date Jul 2, 2018
Online Publication Date Jul 11, 2018
Publication Date Nov 1, 2018
Deposit Date Sep 4, 2018
Publicly Available Date Sep 4, 2018
Journal International Journal of Multiphase Flow
Print ISSN 0301-9322
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 108
Pages 181-201
Keywords Gas-sheared liquid film; Disturbance waves; Bubble entrapment; Bubble size; Bubble velocity; Laser-induced fluorescence
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