Échanges thermiques et tourbillons dans une couche poreuse horizontale

Bories, Serge; Thirriot, C.

doi:10.1051/lhb/1969018

Cited by 12 publications

(7 citation statements)

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“…A direct visualization of the three-dimensional convective flow has been made in a porous layer with a free upper surface (Bories and Thirriot, 1969). When the free liquid layer above the porous medium is fairly thin (about 1 mm for the experiments which are reported here), the horizontal flow pattern along the free surface is closely correlated with the convective flow inside the porous layer.…”

Section: With a Free Upper Surfacementioning

confidence: 94%

Hydrothermal Convection in Saturated Porous Media

Combarnous

1975

Advances in Hydroscience

366

142

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Section: With a Free Upper Surfacementioning

confidence: 94%

Hydrothermal Convection in Saturated Porous Media

Combarnous

1975

Advances in Hydroscience

366

142

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“…Weakly nonlinear analysis predicts two-dimensional roll states near onset for systems with vertical mid-plane symmetry (Busse 1985;Newell & Whitehead 1969;Newell et al 1993). But, in most PMC experiments, when the pattern was determined, it was found to be hexagonal or polygonal (Bories & Thirriot 1969;Lister 1990). An exception is Howle et al (1993aHowle et al ( ,b, 1997, who have obtained straight parallel rolls in some cases, and polygonal patterns in other media, depending on the structure of the medium.…”

Section: Nonlinear Analysis and Convection Patterns Above Onsetmentioning

confidence: 99%

“…An exception is Howle et al (1993aHowle et al ( ,b, 1997, who have obtained straight parallel rolls in some cases, and polygonal patterns in other media, depending on the structure of the medium. Bories & Thirriot (1969) and Nield & Bejan (1992) attribute polygonal patterns to broken symmetry in the boundary conditions. Recently, however, Zimmermann, Sesselberg & Petruccione (1993) have provided an alternative explanation which is consistent with the present work and that of Howle et al They have shown that localized patterns can result if Ra varies randomly in the horizontal plane of the convection layer, a situation which can occur easily for PMC.…”

Section: Nonlinear Analysis and Convection Patterns Above Onsetmentioning

confidence: 99%

“…Prasad, Kulacki & Keyhani (1985) used point measurement techniques by inserting thermocouples into a convection cell to map the temperature. Bories & Thirriot (1969) observed PMC with a free upper surface using aluminium particles sprinkled on a thin layer of fluid above the medium. Beckermann, Viskanta & Ramadhyani (1988) studied a convective system with vertical layers of porous media and clear fluid.…”

Section: Introductionmentioning

confidence: 99%

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Convection and flow in porous media. Part 1. Visualization by magnetic resonance imaging

et al. 1997

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We describe an experimental study of porous media convection (PMC) from onset to 8Ra c . The goal of this work is to provide non-invasive imaging and high-precision heat transport measurements to test theories of convection in PMC. We obtain velocity information and visualize the convection patterns using magnetic resonance imaging (MRI). We study both ordered and disordered packings of mono-disperse spheres of diameter d = 3.204 ± 0.029 mm, in circular, rectangular, and hexagonal planforms. In general, the structure of the medium plays a role which is not predicted by theories which assume a homogeneous system. Disordered media are prepared by pouring mono-disperse spheres into the container. Large ordered regions of close packing for the spheres, with grain boundaries and isolated defects, characterize these media. The defects and grain boundaries play an important role in pattern formation in disordered media. Any deviation from close packing produces a region of larger porosity, hence locally larger permeability. The result is spatial variations in the Rayleigh number, Ra. We define the critical Ra, Ra c , as the Rayleigh number at the onset of convection in the ordered regions. We find that stable localized convective regions exist around grain boundaries and defects at Ra < Ra c . These remain as pinning sites for the convection patterns in the ordered regions as Ra increases above Ra c up to 5Ra c , the highest Ra studied in the disordered media. In ordered media, spheres are packed such that the only deviations from close packing occur within a thin (

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“…Because of the inherent difficulty of imaging the convective process within an opaque medium non-invasively, very limited experimental observations exist of density-driven convection in three-dimensional porous media. In their early seminal work, Bories and Thirriot ( 1969 ) used photographs of the top free surface of a liquid-saturated ( rectangular beadpack to infer fluid movements within the medium itself; most significantly, they demonstrated that cellular structures appear with length scale , which are not possible in two-dimensional settings, as the latter limit the growth of the plume to two orthogonal directions. These findings were later confirmed by Lister ( 1990 ), who used a similar experimental approach and extended these observations to the regime .…”

Section: Introductionmentioning

confidence: 99%

Multidimensional Observations of Dissolution-Driven Convection in Simple Porous Media Using X-ray CT Scanning

et al. 2018

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We present an experimental study of dissolution-driven convection in a three-dimensional porous medium formed from a dense random packing of glass beads. Measurements are conducted using the model fluid system MEG/water in the regime of Rayleigh numbers, . X-ray computed tomography is applied to image the spatial and temporal evolution of the solute plume non-invasively. The tomograms are used to compute macroscopic quantities including the rate of dissolution and horizontally averaged concentration profiles, and enable the visualisation of the flow patterns that arise upon mixing at a spatial resolution of about ( . The latter highlights that under this Ra regime convection becomes truly three-dimensional with the emergence of characteristic patterns that closely resemble the dynamical flow structures produced by high-resolution numerical simulations reported in the literature. We observe that the mixing process evolves systematically through three stages, starting from pure diffusion, followed by convection-dominated and shutdown. A modified diffusion equation is applied to model the convective process with an onset time of convection that compares favourably with the literature data and an effective diffusion coefficient that is almost two orders of magnitude larger than the molecular diffusivity of the solute. The comparison of the experimental observations of convective mixing against their numerical counterparts of the purely diffusive scenario enables the estimation of a non-dimensional convective mass flux in terms of the Sherwood number, . We observe that the latter scales linearly with Ra , in agreement with both experimental and numerical studies on thermal convection over the same Ra regime.

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Échanges thermiques et tourbillons dans une couche poreuse horizontale

Cited by 12 publications

References 0 publications

Hydrothermal Convection in Saturated Porous Media

Hydrothermal Convection in Saturated Porous Media

Convection and flow in porous media. Part 1. Visualization by magnetic resonance imaging

Multidimensional Observations of Dissolution-Driven Convection in Simple Porous Media Using X-ray CT Scanning

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