Power spectral distributions of pseudo-turbulent bubbly flows

Méndez-Díaz, S.; Serrano-García, J. C.; Zenit, Roberto; Hernández‐Cordero, Juan

doi:10.1063/1.4800782

Cited by 48 publications

(47 citation statements)

References 26 publications

(22 reference statements)

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“…In their work bubble-bubble interaction was investigated and the influence of the bubbles on the fluid energy spectra was addressed. A slope of -3.2 of the double-logarithmic energy spectrum of the velocity fluctuation was observed which is in close agreement with (Mendez-Diaz et al, 2013) for a similar configuration. In a previous work Mendez- Diaz et al (2012) collected several experimental results to develop a criterion of void fraction distribution as a function of the bubble Reynolds number and of Weber number.…”

Section: Introductionsupporting

confidence: 87%

Direct Numerical Simulations of spherical bubbles in vertical turbulent channel flow

Santarelli

Fröhlich

2015

International Journal of Multiphase Flow

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Section: Introductionsupporting

confidence: 87%

Direct Numerical Simulations of spherical bubbles in vertical turbulent channel flow

Santarelli

Fröhlich

2015

International Journal of Multiphase Flow

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“…Here, the drag coefficient of a sphere moving at constant velocity in a fluid at rest is estimated by using the correlation of Schiller Riboux et al (2010). Nevertheless, the experimental investigation of a bubble swarm by Mendez-Diaz et al (2013) has not confirmed the validity of the scaling in d/C d for a larger range of Reynolds numbers (70 Re 1000). In the absence of a reliable law for Λ, it cannot be concluded whether the integral length scale measured in the array of spheres is determined by the same mechanism as that of a real bubble swarm or not.…”

Section: Wavenumber Spectra Of Velocity Fluctuationsmentioning

confidence: 99%

“…It is also not proportional to the diameter of bubble, but rather corresponds to the length of the bubble wake (Risso et al 2008). There is, however, no consensus on its exact expression (Mendez-Diaz et al 2013). These two first quantities characterize the large energetic scales of the agitation.…”

Section: Introductionmentioning

confidence: 99%

“…A relevant configuration to isolate the bubble-induced agitation from the other sources of fluctuations is the homogeneous swarm of rising bubbles. In recent years, several works have carried out experimental investigations of this configuration in order to characterize the properties of the bubble-induced agitation (Martinez-Mercado, Palacios-Morales & Zenit 2007;Roig & Larue de Tournemine 2007;Risso et al 2008;Martinez-Mercado et al 2010;Riboux, Risso & Legendre 2010;Mendez-Diaz et al 2013;Colombet et al 2015).…”

Section: Introductionmentioning

confidence: 99%

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Velocity fluctuations generated by the flow through a random array of spheres: a model of bubble-induced agitation

et al. 2017

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To cite this version:Zouhir Amoura, Cédric Besnaci, Frédéric Risso, Véronique Roig. Velocity fluctuations generated by the flow through a random array of spheres: a model of bubble-induced agitation. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2017, 823, pp.592-616. <10.1017/jfm.2017 This work reports an experimental investigation of the flow through a random array of fixed solid spheres. The volume fraction of the spheres is 2 %, and the Reynolds number Re based on the sphere diameter and the average flow velocity is varied from 120 to 1040. Using time and spatial averaging, the fluctuations have been decomposed into two contributions of different natures: a spatial fluctuation that accounts for the strong inhomogeneity of the flow around each sphere, and a time fluctuation that comes from the instability of the flow at large enough Reynolds numbers. The evolutions of these two contributions with the Reynolds number are different, so that their relative importance varies. However, when each is normalized by using its own variance and the integral length scales of the fluctuations, their spectra and probability density functions (PDFs) are almost independent of Re. The spatial fluctuation mostly comes from the velocity deficit in the wakes of the spheres, and is thus dominated by scales larger than one or two sphere diameters. It is found to be responsible for the asymmetry of the PDFs of the vertical fluctuations and of the major part of the anisotropy level between the vertical and the horizontal components of the fluctuations. The time fluctuation dominates at scales smaller than the integral length scale. It is isotropic and its PDFs, well described by an exponential distribution, are non-Gaussian. The spectra of the spatial and the time fluctuations both show an evolution as the power −3 of the wavenumber, but not exactly in the same subrange. All these properties are found in remarkable agreement with the results of both experimental investigations and large eddy simulations (LES) of a homogeneous bubble swarm. This confirms that the main mechanism responsible for the production of bubble-induced fluctuations is the interaction of the velocity disturbances caused by obstacles immersed in a flow and that the structure of this agitation is weakly dependent on the precise nature of the obstacles. The understanding and the modelling of the agitation generated by the motion of a dispersed phase, such as the bubble-induced agitation, therefore require one to distinguish between the roles of these two contributions.

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“…Concerning liquid dynamics, it is now well established that bubble-induced agitation has features that make it different from shear-induced turbulence. A series of experimental investigations carried out in homogeneous columns have led to a rather complete description of its properties (Martínez-Mercado, Palacios-Morales & Zenit 2007;Martínez-Mercado et al 2010;Riboux, Risso & Legendre 2010;Mendez-Diaz, Serrano-García & Zenit 2013). On the other hand, no fundamental investigation of bubble-induced mixing has been performed so far, except for the preliminary work of Mareuge & Lance (1995), which was limited to a single very small value of the gas volume fraction, α = 0.2 %.…”

mentioning

confidence: 97%

Mixing by bubble-induced turbulence

et al. 2015

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This work reports an experimental investigation of the dispersion of a low-diffusive dye within a homogeneous swarm of high-Reynolds-number rising bubbles at gas volume fractions α ranging from 1 % to 13 %. The capture and transport of dye within bubble wakes is found to be negligible and the mixing turns out to result from the bubble-induced turbulence. It is described well by a regular diffusion process. The diffusion coefficient corresponding to the vertical direction is larger than that corresponding to the horizontal direction, owing to the larger intensity of the liquid fluctuations in the vertical direction. Two regimes of diffusion have been identified. At low gas volume fraction, the diffusion time scale is given by the correlation time of the bubble-induced turbulence and the diffusion coefficients increase roughly as α 0.4 . At large gas volume fraction, the diffusion time scale is imposed by the time interval between two bubbles and the diffusion coefficients become almost independent of α. The transition between the two regimes occurs sooner in the horizontal direction (1 % α 3 %) than in the vertical direction (3 % α 6 %). Physical models based on the hydrodynamic properties of the bubble swarm are introduced and guidelines for practical applications are suggested.

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Power spectral distributions of pseudo-turbulent bubbly flows

Cited by 48 publications

References 26 publications

Direct Numerical Simulations of spherical bubbles in vertical turbulent channel flow

Direct Numerical Simulations of spherical bubbles in vertical turbulent channel flow

Velocity fluctuations generated by the flow through a random array of spheres: a model of bubble-induced agitation

Mixing by bubble-induced turbulence

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