Author:
TAKEMURA FUMIO,TAKAGI SHU,MAGNAUDET JACQUES,MATSUMOTO YOICHIRO
Abstract
The two components of the force acting on a clean almost spherical bubble rising
near a plane vertical wall in a quiescent liquid are determined experimentally. This
is achieved by using an apparatus in which a CCD camera and a microscope follow
the rising bubble. This apparatus allows us to measure accurately the bubble radius,
rise speed and distance between the bubble and the wall. Thereby the drag and lift
components of the hydrodynamic force are determined for Reynolds numbers Re
(based on bubble diameter, rise velocity U, and kinematic viscosity ν) less than 40.
The results show the existence of two different regimes, according to the value of
the dimensionless separation L* defined as the ratio between the distance from the
bubble centre to the wall and the viscous length scale ν/U. When L* is O(1) or more,
experimental results corresponding to Reynolds numbers up to unity are found to be
in good agreement with an analytical solution obtained in the Oseen approximation
by adapting the calculation of Vasseur & Cox (1977) to the case of an inviscid bubble.
When L* is o(1), higher-order effects not taken into account in previous analytical
investigations become important and measurements show that the deformation of the
bubble is significant when the viscosity of the surrounding liquid is large enough. In
this regime, experimental results for the drag force and shape of the bubble are found
to agree well with recent theoretical predictions obtained by Magnaudet, Takagi &
Legendre (2002) but the measured lift force tends to exceed the prediction as the
separation decreases.
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
Cited by
81 articles.
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