Author:
POORTE R. E. G.,BIESHEUVEL A.
Abstract
The random motion of nearly spherical bubbles in the turbulent flow behind a grid
is studied experimentally. In quiescent water these bubbles rise at high Reynolds
number. The turbulence is generated by an active grid of the design of Makita (1991),
and can have turbulence Reynolds number Rλ of up to 200. Minor changes in the
geometry of the grid and in its mode of operation improves the isotropy of the
turbulence, compared with that reported by Makita (1991) and Mydlarski & Warhaft
(1996). The trajectory of each bubble is measured with high spatial and temporal
resolution with a specially developed technique that makes use of a position-sensitive
detector. Bubble statistics such as the mean rise velocity and the root-mean-square
velocity fluctuations are obtained by ensemble averaging over many identical bubbles.
The resulting bubble mean rise velocity is significantly reduced (up to 35%) compared
with the quiescent conditions. The vertical bubble velocity fluctuations are found to
be non-Gaussian, whereas the horizontal displacements are Gaussian for all times.
The diffusivity of bubbles is considerably less than that of fluid particles. These
findings are qualitatively consistent with results obtained through theoretical analysis
and numerical simulations by Spelt & Biesheuvel (1997).
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
Cited by
121 articles.
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