Interaction between two localized fluidization cavities in granular media : Experiments and numerical simulation

Ngoma, Jeff; Bonelli, Stéphane; Philippe, Pierre; Delenne, Jean‐Yves; Radjaï, Farhang

doi:10.1201/b17395-286

Cited by 7 publications

(10 citation statements)

References 2 publications

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“…A typical configuration for laboratory experiments on localized fluidization is shown in figure 1. The previous works on such configurations evidenced three successive regimes during a gradual increase of the injection rate [20,14,15]. At very low rates, the bed is stable.…”

Section: Introductionmentioning

confidence: 88%

“…The behavior of a granular bed subjected to localized upward flux can be investigated using different coupled DEM-fluid models. Some previous works were based on couplings between the DEM and the Lattice Boltzmann [23] (LBM) method in two dimensions [19,20,24,25].…”

Section: Numerical Modelmentioning

confidence: 99%

“…Despite the large number of works dedicated to fluidized beds [16,17,18], only a few have focused on the initial and developing phases of a localized fluidized zone inside a granular medium [19,20,14,15]. The present study is devoted to this specific aspect.…”

Section: Introductionmentioning

confidence: 98%

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Localized fluidization in granular materials: Theoretical and numerical study

et al. 2016

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We present analytical and numerical results on localized fluidization within a granular layer subjected to a local injection of fluid. As the injection rate increases the three different regimes previously reported in the literature are recovered: homogeneous expansion of the bed, fluidized cavity in which fluidization starts developing above the injection area, and finally the chimney of fluidized grains when the fluidization zone reaches the free surface. The analytical approach is at the continuum scale, based on Darcy's law and Therzaghi's effective stress principle. It provides a good description of the phenomenon as long as the porosity of the granular assembly remains relatively homogeneous, i.e., for small injection rates. The numerical approach is at the particle scale based on the coupled discrete element method and a pore-scale finite volume method. It tackles the more heterogeneous situations which occur at larger injection rates. The results from both methods are in qualitative agreement with data published independently. A more quantitative agreement is achieved by the numerical model. A direct link is evidenced between the occurrence of the different regimes of fluidization and the injection aperture. While narrow apertures let the three different regimes be distinguished clearly, larger apertures tend to produce a single homogeneous fluidization regime. In the former case, it is found that the transition between the cavity regime and the chimney regime for an increasing injection rate coincides with a peak in the evolution of inlet pressure. Finally, the occurrence of the different regimes is defined in terms of the normalized flux and aperture.

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Section: Introductionmentioning

confidence: 88%

Section: Numerical Modelmentioning

confidence: 99%

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Localized fluidization in granular materials: Theoretical and numerical study

et al. 2016

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“…Despite many significant improvements, as witnessed by the abovecited literature, both modelling and computational issues still remain, even if promising studies of localized fluidization cavities in granular beds can be found (e.g. Ngoma et al (2015)). …”

Section: Concluding Remarks Perspectivesmentioning

confidence: 99%

Buoyancy-driven destabilization of an immersed granular bed

et al. 2018

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Under suitable conditions, an immersed granular bed can be destabilized by local thermal forcing and the induced buoyant force. The destabilization is evident from the triggering and establishment of a dense fluid-like granular plume. Varying the initial granular layer average height h, time series of the free layer surface are extracted, allowing us to dynamically compute the underlying volume of the granular layer. The initial interface deformation, the lowering of the average granular interface (i.e. decrease of the granular layer volume) and the emission of a plume are observed and analyzed. We show that the phenomenon is mainly driven by heat transfer, for large h and also involves variable height thermal boundary condition & Darcy's flow triggering, for small h. Simple modeling with no adjustable parameter not only allows us to capture the observed scaling power laws but is also in quantitative agreement with the obtained experimental data.

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“…The granular layer is initially at static equilibrium then subjected to one or several local injections of fluid through the bottom face of the box (figure 1). The previous works on such configurations evidenced three successive regimes during a gradual increase of the injection rate [4][5][6][7]. At very low rates, the bed is stable.…”

Section: Introductionmentioning

confidence: 99%

From continuum analytical description to discrete numerical modelling of localized fluidization in granular media

Montellà¹,

Toraldo²,

Sibille³

2017

EPJ Web Conf.

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Abstract. We present analytical and numerical results on localized fluidization within a granular layer subjected to a local injection of fluid. As the injection rate increases the three different regimes previously reported in the literature are recovered: homogeneous expansion of the bed, fluidized cavity in which fluidization starts developing above the injection area, and finally the chimney of fluidized grains when the fluidization zone reaches the free surface. The analytical approach is at the continuum scale, based on Darcy's law and Therzaghi's effective stress principle. It provides a good description of the phenomenon as long as the porosity of the granular assembly remains relatively homogeneous. The numerical approach is at the particle scale based on the coupled DEM-PFV method. It tackles the more heterogeneous situations which occur at larger injection rates. A direct link is evidenced between the occurrence of the different regimes of fluidization and the injection aperture. Finally, the merging of chimneys in case of two injection points is investigated.

show abstract

Interaction between two localized fluidization cavities in granular media : Experiments and numerical simulation

Cited by 7 publications

References 2 publications

Localized fluidization in granular materials: Theoretical and numerical study

Localized fluidization in granular materials: Theoretical and numerical study

Buoyancy-driven destabilization of an immersed granular bed

From continuum analytical description to discrete numerical modelling of localized fluidization in granular media

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