90009448

open access

Accepted Manuscript

CRITICAL DIAMETER FOR LIFT REVERSAL OF BUBBLES IN LINEAR SHEAR FLOWS

English (英語)

Multiphase Science and Technology

33(2)

69-85

Begell House

2021

2022-07-07

The lift coefficient CL of a bubble in a shear flow is known to change its sign depending on the bubble shape, i.e., CL of spherical bubbles are positive for any bubble Reynolds numbers, while those of ellipsoidal bubbles can be negative due to the deformation-induced negative lift. The critical bubble diameter dC for the lift reversal was discussed in this study by making use of available CL correlations for clean bubbles in linear shear flows. As a result, the following conclusions were obtained: (1) the CL correlations well describe the complex characteristics of dC, and the lift reversal criterion in terms of ReC is well reproduced with the correlations; (2) in the surface tension and inertial force dominant regime, the critical Eötvös and Weber numbers can be used to develop a simple criterion of lift reversal, i.e., they are almost constant, and the capillary number for dC can be expressed in terms of the Morton number only, M; these dimensionless groups in the viscous force dominant regime however show more complex dependence on M; and (3) the critical Ohnesorge number OhC monotonically increases with increasing M even in the viscous force dominant regime. Therefore a tentative dC correlation based on OhC was developed.

Shape deformation

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