Experimental study of 3D Rayleigh–Taylor convection between miscible fluids in a porous medium

Nakanishi, Yuji; Hyodo, Akimitsu; Wang, Lei; Suekane, Tetsuya

doi:10.1016/j.advwatres.2016.09.015

Cited by 49 publications

(37 citation statements)

References 46 publications

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“…The pore volume (PV) was calculated by considering the difference between the water-flooded cylinder and non-flooded cylinder was 36.6 mL, and the porosity (ϕ) was 0.50. for visualization [17,18]. Recently, 3D visualization schemes like X-ray computer tomography (CT) [19,[23][24][25][26] and magnetic resonance imaging [27][28][29] emerged for visualization of fluid flow in porous media. Berg et al [19] examined the development patterns of fingering from the interaction of viscous fingering and gravity underrun in Berea sandstone cores, for miscible fluids over a wide range of scaling parameters using X-ray CT.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Three-Dimensional Interaction of Viscous Fingering and Gravitational Segregation in Porous Media

Suekane

Koe

Barbancho

2019

Fluids

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Viscous fingering is fluid dynamics instability induced on the displacement front when a less viscous fluid (LVF) displaces a more viscous fluid (MVF), thereby reducing the displacement efficiency. The displacement of a denser fluid by a less dense fluid produces a gravitational tongue. This gravitational segregation also reduces the displacement efficiency. In this study, the three-dimensional structure of the fingering pattern at the viscous fingering to gravitational segregation boundary was examined using X-ray microtomography on a packed bed of particles. At low gravity numbers, viscous fingering resembled that without gravity characterized by nonlinear interaction including tip-splitting, shielding, and coalescence. At intermediate gravity numbers, viscous fingering is associated with the gravitational tongue due to segregation. At high gravity numbers, a clear gravitational tongue penetrates from the inlet to the outlet. Consequently, the concentration near the injection point decreases and exhibits a flat profile in the flow direction. The displacement efficiency decreases with increasing gravity number, with the highest value achieved without gravity but depends on many factors, including the viscosity ratio and Péclet number.

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Section: Experimental Apparatusmentioning

confidence: 99%

Three-Dimensional Interaction of Viscous Fingering and Gravitational Segregation in Porous Media

Suekane

Koe

Barbancho

2019

Fluids

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“…Assuming the steady state in the distribution of the concentration in the most extended finger, we evaluated the transverse dispersion coefficient by mass conservation for cylindrical control volume of the finger. Details of the scheme used to estimate the transverse dispersion are found in Nakanishi et al (2016) and Wang et al (2016). Figure 6 plots the transverse dispersion against the Péclet number defined as Pe = (vdp)/(φD0), where v is the finger extension velocity.…”

Section: Onset Timementioning

confidence: 99%

“…A local maximum in NaI concentration was detected as a finger for each slice. The details of the scheme used to detect fingers and the property of evolution of the finger number density can be found in Nakanishi et al (2016). In Fig.…”

Section: Finger Number Densitymentioning

confidence: 99%

“…The total mass remained zero before the onset of convection and increased proportionally with time after a certain period of time after the onset. The onset time was estimated from the intersection of these two lines (see Nakanishi et al (2016) for details). For a certain permeability of the porous media, for example dp = 215 µm, the onset time increased proportionally with the thickness of the interface.…”

Section: Onset Timementioning

confidence: 99%

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Effect of diffusing layer thickness on the density-driven natural convection of miscible fluids in porous media: Modeling of mass transport

Wang¹,

Nakanishi²,

Teston³

et al. 2018

JFST

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In this study, density-driven natural convection in porous media associated with Rayleigh-Taylor instability was visualized by X-ray computed tomography to investigate the effect of the thickness of the diffusing interface on convection. The thickness of the interface was changed by molecular diffusion with time, and the effective diffusivity in a porous medium was estimated. Compared with the thick interface, for the thin interface, many fine fingers formed and extended rapidly in a vertical direction. The onset time of natural convection increased proportionally with the thickness of the interface, being correlated with Rayleigh number and Péclet number. For the thinner initial interface, the finger number density increased more rapidly after onset and reached a higher value. Next, we discussed the mass transport in Rayleigh-Taylor convection to show how dispersion affects mass transport based on finger extension velocity and concentration in fingers. Increasing the interface thickness delayed the onset of convection, while the finger extension velocity remained the same. The reduced finger extension velocity changed nonlinearly with the Péclet number, reflecting the effect of dispersion. High transverse dispersion and longitudinal dispersion quickly reduced finger density. Transverse dispersion between ascending and descending fingers decreased the density; the density decreased linearly along the finger on both sides of the symmetric plane. As a result, the Sherwood number was proportional to the Rayleigh number, whereas the coefficient changed nonlinearly with Péclet number because of dispersion, reflecting the nonlinear dependences of the reduced velocity and the reduced density difference on Péclet number.

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“…Hydrodynamic dispersion, particularly mechanical dispersion, has an impact on the structure of fingers in density-driven nature convection. Recent experimental studies found that hydrodynamic dispersion enhances the merging of fingers and thus reduces the finger numbers [107][108][109]. Such a process indicates an effect of hydrodynamic dispersion on dilution and reactive mixing of solute fingers in density-driven natural convection.…”

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confidence: 97%

Recent Advances in Experimental Studies of Steady-State Dilution and Reactive Mixing in Saturated Porous Media

Zhang

et al. 2018

Water

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Transverse dispersive mixing plays an important role in controlling natural attenuation of contaminant plumes and the performance of engineered remediation strategies. The extent of transverse mixing can be significantly affected by porous media heterogeneity and anisotropy. For instance, flow focusing in the high-permeability inclusions leads to an enhancement of dilution and reactive mixing in steady-state solute transport. Numerous modeling studies have been performed to understand the mechanism of conservative and reactive transport in homogeneous and complex heterogeneous porous media. However, experimental investigations are necessary to show an intuitive phenomenon and to validate the modeling results. This paper briefly reviews recent laboratory experimental studies on dilution and reactive mixing of steady-state transport in saturated homogeneous and heterogeneous porous media. In this context, setups and measuring techniques are described in pore-scale and Darcy-scale experiments. Parameters quantifying dilution and reactive mixing in the experiments are also introduced. Finally, we discuss the further experimental works necessary to deepen our understanding of dilution and reactive mixing in natural aquifers.At steady-state conditions, transverse dispersive mixing is the key process determining the length of the plume and the fate of the contaminant transport [6][7][8][9][10][11]. Even though the transverse dispersion coefficient is smaller than the longitudinal dispersion coefficient, contact areas between the mixing solutions are much larger in the transverse direction compared to the longitudinal direction. Only at the front of the plume does longitudinal dispersion play an important role in steady-state plume transport. This can be reflected by the steep concentration gradients found at the fringes of groundwater plumes in the field investigations of contaminant aquifers [12][13][14][15].Observation and measuring points in the field investigation of contaminant transport are generally coarse. Furthermore, the heterogeneity and anisotropy of porous media and the biogeochemical complexity of natural aquifer systems influence dilution and mixing. The interpretation separating different physical and chemical processes and the influencing factors is difficult in natural groundwater systems. A detailed analysis of the pure transverse dispersive mixing process and its influencing factors under well-defined and controlled conditions is only possible by performing laboratory experiments and numerical simulations. Numerous modeling studies have been conducted to investigate transverse dispersion of conservative and reactive solutes in homogeneous and heterogeneous porous media [16][17][18][19]. However, a major challenge of various numerical methods is their numerical dispersion and the resulting uncertainties. Therefore, laboratory experiments are always necessary to give an intuitive view of the phenomenon and to test and verify the numerical models.The objectives of this paper are to give a brief review o...

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Experimental study of 3D Rayleigh–Taylor convection between miscible fluids in a porous medium

Cited by 49 publications

References 46 publications

Three-Dimensional Interaction of Viscous Fingering and Gravitational Segregation in Porous Media

Three-Dimensional Interaction of Viscous Fingering and Gravitational Segregation in Porous Media

Effect of diffusing layer thickness on the density-driven natural convection of miscible fluids in porous media: Modeling of mass transport

Recent Advances in Experimental Studies of Steady-State Dilution and Reactive Mixing in Saturated Porous Media

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