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Papers by Jean-françois Thovert

Le Centre pour la Communication Scientifique Directe - HAL - Diderot, 2008

The basic properties of fracture networks are derived numerically and rationalized. Simple formul... more The basic properties of fracture networks are derived numerically and rationalized. Simple formulas are provided for an easy estimation of orders of magnitude, based on the excluded volume, on an associated dimensionless density and on shape factors. A general correlation is proposed for the percolation threshold in various types of networks, the blocks which are cut in the solid matrix by the network are characterized and an empirical formula is proposed for the permeability.

Theory and Applications of Transport in Porous Media, 1999

Le Centre pour la Communication Scientifique Directe - HAL - INSU, Mar 2, 2009

Transport in Porous Media, 2020

The increasing access to 3d digital images of porous media provides an ideal avenue for the deter... more The increasing access to 3d digital images of porous media provides an ideal avenue for the determination of their transport properties, by solving the governing equations in their actual microscale geometry and evaluating the tensor coefficient that relates the mean flux and driving gradient. However, the first and puzzling question along the way is the choice of the conditions to be imposed for this resolution at the boundaries of the sample. This methodological issue is explored here with the purpose of quantifying the influence of the boundary conditions (BC) in relation with the parameters of the system (porosity, characteristic length scale of the microstructure, ratio of the phase conductivities), assessing the level of confidence associated with the predictions, devising criteria to anticipate the risk of serious artifacts, and if possible proposing ways to limit them. Although the terminology of thermal transfer is used, the developments apply to the upscaling of any transport property governed by a diffusion equation, including thermal or electrical conduction, mass diffusion or Darcy flow. Quantitative indicators are introduced for a rigorous individual or comparative assessment of conductivity tensors, and they are used in the analysis of the results of extensive calculations based on four tomographic images of various kinds of porous materials, with a broad range of conductivity contrasts, and various kinds of BC's. Ultimately, practical criteria are proposed for the a priori and a posteriori detection of at-risk situations, and a self-diagnosing protocol is proposed to screen out the influence of the BC's, when this is possible.

Theory and Applications of Transport in Porous Media, 1999

This Chapter is devoted to the geometrical properties of a single fracture, with emphasis on the ... more This Chapter is devoted to the geometrical properties of a single fracture, with emphasis on the conceptual tools used to characterize and simulate a real fracture, and with the purpose of predicting its transport properties. As a general rule, the point of view is microscopic. The fracture is generally supposed to extend indefinitely, and its local properties are discussed.

Geophysical Research Letters, 2014

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-... more This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

The European Physical Journal B, 2001

Two-scale porous media are generated by filtering a Gaussian random correlated field with a rando... more Two-scale porous media are generated by filtering a Gaussian random correlated field with a random correlated threshold field. The percolation threshold and the critical exponent ν are derived with the help of a finite-size scaling method. The percolation threshold for the three-dimensional media is a decreasing function of the variance and correlation length of the threshold field. A simplified model predicts these trends in 3d; moreover, it suggested some effects in 2d which were all numerically verified.

Journal of Fluid Mechanics, 2021

This work addresses the question of a pertinent macroscale model describing creeping, incompressi... more This work addresses the question of a pertinent macroscale model describing creeping, incompressible and single-phase ow of a Newtonian uid in an exuding, rigid and homogeneous porous medium. The macroscopic model is derived by upscaling the porescale Stokes equations considering a normal mass ux at the solid-uid interface. The upscaled mass equation shows that the average velocity is non-solenoidal. In addition, the macroscopic momentum equation involves a Darcy term with the classical permeability tensor accounting for macroscopic drag and a correction velocity vector which is a signature of the local uid displacements induced by the exuding phenomenon. This correction is the sum of a term accounting for the local exuding eect and a compensation term associated to the assumption of spatial periodicity. The rst term, as well as the permeability tensor, are obtained from the solution of the same unique and intrinsic closure problem, which corresponds to the one involved in classical Darcy's law. The upscaled model is validated by comparisons with pore-scale numerical simulations in several illustrative examples. The dierent congurations evidence the richness of the problem, despite the apparent simplicity of its formulation. The results of this work motivate further investigation about the inuence of internal ow sources in transport phenomena in porous media.

During industrial, geoscientific or environmental drilling campaigns, rock samples are often extr... more During industrial, geoscientific or environmental drilling campaigns, rock samples are often extracted few km below surface under large pressures p and their in situ properties may significantly differ from the ones measured in the lab close to atmospheric pressure p_a. Our first objective is to derive from measurements made at p_a the geometric and transport properties at p. In petroleum

Transport in Porous Media, 2016

OATAO is an open access repository that collects the work of Toulouse researchers and makes it fr... more OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible.

Fractured Porous Media, 2012

Fractured Porous Media, 2012

In this paper, a spectroscopic setup aiming to characterize thermal radiative properties of both ... more In this paper, a spectroscopic setup aiming to characterize thermal radiative properties of both homogenous and heterogeneous materials is described. In particular the normal spectral emittance of oxide mineral compounds such as SiO 2 , Al 2 O 3 , MgO among others, is accessible on a large domain of wavelengths (0.8-1000 µm) and on a large domain of temperature (500-2500 K). As expected, these compounds show a radiative behaviour that is typical of semitransparent materials. On the other hand, the study of the pyrolysis process of Moroccan oil shale grains indicates that the latter species are observed in their chemical compositions for T > 1000 K. This precise knowledge of radiative and structural properties allows to propose a possible strategy of modelling taking account for absorption/scattering processes which occur within this material, when it undergoes a combustion process.

Journal of Colloid and Interface Science, 2010

Three dimensional samples of three different foams are obtained by microtomography. The macroscop... more Three dimensional samples of three different foams are obtained by microtomography. The macroscopic conductivity and permeability of these foams are calculated by three different numerical techniques based on either a finite volume discretization or Lattice Boltzmann algorithm. Permeability is also measured and an excellent agreement is obtained between the various estimations. Calculated conductivities are successfully compared to available data.

Le Centre pour la Communication Scientifique Directe - HAL - Diderot, 2008

The basic properties of fracture networks are derived numerically and rationalized. Simple formul... more The basic properties of fracture networks are derived numerically and rationalized. Simple formulas are provided for an easy estimation of orders of magnitude, based on the excluded volume, on an associated dimensionless density and on shape factors. A general correlation is proposed for the percolation threshold in various types of networks, the blocks which are cut in the solid matrix by the network are characterized and an empirical formula is proposed for the permeability.

Theory and Applications of Transport in Porous Media, 1999

Le Centre pour la Communication Scientifique Directe - HAL - INSU, Mar 2, 2009

Transport in Porous Media, 2020

The increasing access to 3d digital images of porous media provides an ideal avenue for the deter... more The increasing access to 3d digital images of porous media provides an ideal avenue for the determination of their transport properties, by solving the governing equations in their actual microscale geometry and evaluating the tensor coefficient that relates the mean flux and driving gradient. However, the first and puzzling question along the way is the choice of the conditions to be imposed for this resolution at the boundaries of the sample. This methodological issue is explored here with the purpose of quantifying the influence of the boundary conditions (BC) in relation with the parameters of the system (porosity, characteristic length scale of the microstructure, ratio of the phase conductivities), assessing the level of confidence associated with the predictions, devising criteria to anticipate the risk of serious artifacts, and if possible proposing ways to limit them. Although the terminology of thermal transfer is used, the developments apply to the upscaling of any transport property governed by a diffusion equation, including thermal or electrical conduction, mass diffusion or Darcy flow. Quantitative indicators are introduced for a rigorous individual or comparative assessment of conductivity tensors, and they are used in the analysis of the results of extensive calculations based on four tomographic images of various kinds of porous materials, with a broad range of conductivity contrasts, and various kinds of BC's. Ultimately, practical criteria are proposed for the a priori and a posteriori detection of at-risk situations, and a self-diagnosing protocol is proposed to screen out the influence of the BC's, when this is possible.

Theory and Applications of Transport in Porous Media, 1999

This Chapter is devoted to the geometrical properties of a single fracture, with emphasis on the ... more This Chapter is devoted to the geometrical properties of a single fracture, with emphasis on the conceptual tools used to characterize and simulate a real fracture, and with the purpose of predicting its transport properties. As a general rule, the point of view is microscopic. The fracture is generally supposed to extend indefinitely, and its local properties are discussed.

Geophysical Research Letters, 2014

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-... more This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

The European Physical Journal B, 2001

Two-scale porous media are generated by filtering a Gaussian random correlated field with a rando... more Two-scale porous media are generated by filtering a Gaussian random correlated field with a random correlated threshold field. The percolation threshold and the critical exponent ν are derived with the help of a finite-size scaling method. The percolation threshold for the three-dimensional media is a decreasing function of the variance and correlation length of the threshold field. A simplified model predicts these trends in 3d; moreover, it suggested some effects in 2d which were all numerically verified.

Journal of Fluid Mechanics, 2021

This work addresses the question of a pertinent macroscale model describing creeping, incompressi... more This work addresses the question of a pertinent macroscale model describing creeping, incompressible and single-phase ow of a Newtonian uid in an exuding, rigid and homogeneous porous medium. The macroscopic model is derived by upscaling the porescale Stokes equations considering a normal mass ux at the solid-uid interface. The upscaled mass equation shows that the average velocity is non-solenoidal. In addition, the macroscopic momentum equation involves a Darcy term with the classical permeability tensor accounting for macroscopic drag and a correction velocity vector which is a signature of the local uid displacements induced by the exuding phenomenon. This correction is the sum of a term accounting for the local exuding eect and a compensation term associated to the assumption of spatial periodicity. The rst term, as well as the permeability tensor, are obtained from the solution of the same unique and intrinsic closure problem, which corresponds to the one involved in classical Darcy's law. The upscaled model is validated by comparisons with pore-scale numerical simulations in several illustrative examples. The dierent congurations evidence the richness of the problem, despite the apparent simplicity of its formulation. The results of this work motivate further investigation about the inuence of internal ow sources in transport phenomena in porous media.

During industrial, geoscientific or environmental drilling campaigns, rock samples are often extr... more During industrial, geoscientific or environmental drilling campaigns, rock samples are often extracted few km below surface under large pressures p and their in situ properties may significantly differ from the ones measured in the lab close to atmospheric pressure p_a. Our first objective is to derive from measurements made at p_a the geometric and transport properties at p. In petroleum

Transport in Porous Media, 2016

OATAO is an open access repository that collects the work of Toulouse researchers and makes it fr... more OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible.

Fractured Porous Media, 2012

Fractured Porous Media, 2012

In this paper, a spectroscopic setup aiming to characterize thermal radiative properties of both ... more In this paper, a spectroscopic setup aiming to characterize thermal radiative properties of both homogenous and heterogeneous materials is described. In particular the normal spectral emittance of oxide mineral compounds such as SiO 2 , Al 2 O 3 , MgO among others, is accessible on a large domain of wavelengths (0.8-1000 µm) and on a large domain of temperature (500-2500 K). As expected, these compounds show a radiative behaviour that is typical of semitransparent materials. On the other hand, the study of the pyrolysis process of Moroccan oil shale grains indicates that the latter species are observed in their chemical compositions for T > 1000 K. This precise knowledge of radiative and structural properties allows to propose a possible strategy of modelling taking account for absorption/scattering processes which occur within this material, when it undergoes a combustion process.

Journal of Colloid and Interface Science, 2010

Three dimensional samples of three different foams are obtained by microtomography. The macroscop... more Three dimensional samples of three different foams are obtained by microtomography. The macroscopic conductivity and permeability of these foams are calculated by three different numerical techniques based on either a finite volume discretization or Lattice Boltzmann algorithm. Permeability is also measured and an excellent agreement is obtained between the various estimations. Calculated conductivities are successfully compared to available data.