Masahiro Muraoka, Tsubasa Takamizawa

Abstract:

The creeping motion and coalescence of droplets rising in a vertical tube filled with a quiescent fluid are experimentally examined. The viscosity ratio of a droplet to the surrounding fluid is unity, keeping the undeformed diameter of the leading droplet constant while varying the kinematic viscosities of the droplet and surrounding fluid, as well as the diameter of the following droplet. The creeping motion of droplets can be divided into three types. The coalescence times of two droplets are measured. The diameter of the clearance area between them is also measured immediately before coalescence. The experimentally measured coalescence times are compared with the coalescence times of droplets predicted using a semi-theoretical formula. The forces acting on the thin film between the droplets are discussed.

Keywords: Coalescence, Droplet, Creeping motion, Vertical tube, Quiescent fluid.

Date Published: April 28, 2025
DOI: 10.11159/jffhmt.2025.015

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