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Characterization of turbulence in rectangular bubble column

Authors: Sathe, Mayur; Joshi, Jyeshtharaj; Evans, Geoffrey;

Characterization of turbulence in rectangular bubble column

Abstract

Abstract Turbulence in bubbly flows is of utmost practical and theoretical interest. In the current work, particle image velocimetry (PIV) measurements have been carried out in a rectangular bubble column. The superficial gas velocity was varied from 2 mm/s to 20 mm/s, with the gas hold-up values up to 4.75%. Both the homogeneous and heterogeneous regimes of operation were covered for the bubble column. Prior to turbulence measurement with PIV the bubble size distribution, time averaged velocity profile, and gas hold-up profile were measured with high speed camera and modified Pitot tube probe. In order to resolve low speed (large scale) and high speed (small scale) flow structures in a column properly, measurements were carried out with a low speed (7 Hz) and high speed (900 Hz) PIV system. Image processing program to identify bubbles from PIV image and mask the PIV vector field was developed. The energy spectrum of the liquid phase turbulence was calculated from PIV velocity field with FFT. Wavelet transform was used to separate small scale fluctuations from large scale fluctuations in liquid velocity field. Energy spectrum of large scale fluctuations was found to be dependent on the sparger type, while energy spectrum of small scale fluctuations was found to be similar for all spargers. The spectral slope of inertial subrange was found to be close to −5/3. The spectral slope for wavenumber higher than inertial subrange was found to be −3. Reasoning for this behavior based on energy transfer and energy dissipation rate has been provided.

Country
Australia
Keywords

fluid mechanics, turbulence, energy spectrum, imaging, 532, PIV, bubble colums

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citations
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
33
Top 10%
Top 10%
Top 10%
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