Motions of single silicon oil drops rising in linear shear flows of glycerol-water solutions are measured to investigate the effects of the viscosity ratio κ and dimensionless shear rate Sr on drag forces under the conditions of −6.3 ≤ logM ≤ −4.8, 0.94 ≤ κ7.04, 1 < Re ≤ 23 and 3.2 ≤ ω ≤ 6.0 s−1, where M is the Morton number and ω the magnitude of the velocity gradient of the continuous phase. As a result, we confirmed that (1) the drag coefficient CD of a drop in a linear shear flow takes a higher value than the drag coefficient CD0 of the same-size drop in a stagnant liquid, (2) CD/CD0 increases with Sr, and (3) the augmentation of CD becomes large as κ increases.

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