Morphology of air invasion in an immersed granular layer

Varas, Germán; Vidal, Valérie; Géminard, Jean‐Christophe

doi:10.1103/physreve.83.061302

Cited by 17 publications

(40 citation statements)

References 26 publications

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“…This parabolic shape has already been described in the literature [17,21,37,46], although for many years a cone-shape invasion zone has also been reported [17]. More recent works have pointed out the robustness of the parabolic shape, whichever the initial invasion regime, i.e., whichever the injection flow-rate, both in 2D and 3D experiments [42][43][44]. Based on these results and our experiments, we propose the tentative diagram displayed in Figure 2, where for a given immersed granular bed, the state of the system will be mainly governed by the injection flow rate, Q, as well as the volume of gas V(t) which has crossed the grain layer at time t.…”

Section: Methodsmentioning

confidence: 87%

“…Previous studies have described the fluidized zone (FZ) parabolic contour by the equation |x| = √ Dz, where D can be seen as the analog of a diffusion coefficient-here, D is a characteristic "diffusive" length [42]. Typically, in similar experiments, D was found of the order of 4 cm [44].…”

Section: Dependence On Q and Dmentioning

confidence: 84%

“…Although it is not possible to visualize it directly in the 3D experiment, mapping the air location at the free surface of the granular layer also provided a good description of the region invaded by the air, as a function of the bed height [42]. For most experiments, the stationary shape of the fluidized zone is a parabola.…”

Section: Methodsmentioning

confidence: 99%

“…A simple analytical model can account for the final parabolic shape [42] and its independence on the flow rate. It points out that the dynamics of the system is governed by a single dimensionless parameter:…”

Section: Methodsmentioning

confidence: 99%

“…In some experiments, we can monitor simultaneously the overpressure P in the chamber, which provides indication on the system dynamics. a granular material immersed in water [18,21,37,38,[42][43][44], and propose a tentative regime diagram. As already reported in the literature, the fluidized zone exhibits a parabolic shape, in the stationary regime, for most of the experimental parameters.…”

Section: Introductionmentioning

confidence: 99%

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Flow and fracture in water-saturated, unconstrained granular beds

et al. 2015

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The injection of gas in a liquid-saturated granular bed gives rise to a wide variety of invasion patterns. Many studies have focused on constrained porous media, in which the grains are fixed in the bed and only the interstitial fluid flows when the gas invades the system. With a free upper boundary, however, the grains can be entrained by the ascending gas or fluid motion, and the competition between the upward motion of grains and sedimentation leads to new patterns. We propose a brief review of the experimental investigation of the dynamics of air rising through a water-saturated, unconstrained granular bed, in both two and three dimensions. After describing the invasion pattern at short and long time, a tentative regime-diagram is proposed. We report original results showing a dependence of the fluidized zone shape, at long times, on the injection flow rate and grain size. A method based on image analysis makes it possible to detect not only the fluidized zone profile in the stationary regime, but also to follow the transient dynamics of its formation. Finally, we describe the degassing dynamics inside the fluidized zone, in the stationary regime. Depending on the experimental conditions, regular bubbling, continuous degassing, intermittent regime or even spontaneous flow-to-fracture transition are observed.

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Section: Methodsmentioning

confidence: 87%

Section: Dependence On Q and Dmentioning

confidence: 84%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Flow and fracture in water-saturated, unconstrained granular beds

et al. 2015

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Flow‐to‐fracture transition in a volcanic mush plug may govern normal eruptions at Stromboli

Suckale

Keller

Cashman

et al. 2016

Geophysical Research Letters

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Stromboli is a model volcano for studying eruptions driven by degassing. The current paradigm posits that Strombolian eruptions represent the bursting of gas slugs ascending through melt‐filled conduits, but petrological observations show that magma at shallow depth is crystalline enough to form a three‐phase plug consisting of crystals, bubbles, and melt. We combine a 1‐D model of gas flushing a crystalline mush with a 3‐D stress model. Our results suggest that localized gas segregation establishes hot conduits of mobile magma within a stagnant plug. The plug is prone to tensile failure controlled by gas overpressure and tectonic stress, with failure most likely beneath the observed vent locations. We hence argue that Strombolian eruptions are related to plug failure rather than flow. Our proposed three‐phase model of the shallow plumbing system may provide a promising framework for integrating geophysical, petrological, and morphological observations at Stromboli and in open‐system volcanism more generally.

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Air invasion in a granular layer immersed in a fluid: morphology and dynamics

2013

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We investigate the morphology and dynamics of the region invaded by air injected at the bottom of an immersed granular bed. Previous experimental results point out the formation of a fluidized zone with a parabolic shape which does not depend, in the stationary regime, on the injection flow-rate. By tilting the experiment, we can tune the effective gravity in the system. We show that it does not affect significantly the morphology either. A numerical study made it possible to access the typical height and width of the structure, which are governed by the relative effects of gravity and capillarity. After a brief review on this subject, we propose first, new experimental observations on the air invasion regimes and on the morphology of the fluidized zone, in particular its growth dynamics; then, we complement the previous numerical study by considering the influence of the bottom boundary condition. In particular, we quantify the morphology of the invaded region when the gas is injected in the bulk, thus when air is likely to propagate downwards. These results are of practical importance in the prediction of the morphol-

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Morphology of air invasion in an immersed granular layer

Cited by 17 publications

References 26 publications

Flow and fracture in water-saturated, unconstrained granular beds

Flow and fracture in water-saturated, unconstrained granular beds

Flow‐to‐fracture transition in a volcanic mush plug may govern normal eruptions at Stromboli

Air invasion in a granular layer immersed in a fluid: morphology and dynamics

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