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Experiments on the motion of gas bubbles in turbulence generated by an active grid

Published online by Cambridge University Press:  11 July 2002

R. E. G. POORTE  and
A. BIESHEUVEL
R. E. G. POORTE
Affiliation:
J. M. Burgers Centre for Fluid Mechanics, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands Present address: Shell International Exploration and Production BV, PO Box 60, 2280 AB Rijswijk, The Netherlands.
A. BIESHEUVEL
Affiliation:
J. M. Burgers Centre for Fluid Mechanics, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands
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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).

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 461 , 25 June 2002 , pp. 127 - 154
Copyright
© 2002 Cambridge University Press

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