Numerical investigation of dynamic capillary pressure in two-phase flow in porous medium

summary:In order to investigate effects of the dynamic capillary pressure-saturation relationship used in the modelling of a flow in porous media, a one-dimensional fully implicit numerical scheme is proposed. The numerical scheme is used to simulate an experimental procedure using a measured dataset for the sand and fluid properties. Results of simulations using different models for the dynamic effect term in capillary pressure-saturation relationship are presented and discussed

TNL: NUMERICAL LIBRARY FOR MODERN PARALLEL ARCHITECTURES

We present Template Numerical Library (TNL, www.tnl-project.org) with native support of modern parallel architectures like multi–core CPUs and GPUs. The library offers an abstract layer for accessing these architectures via unified interface tailored for easy and fast development of high-performance algorithms and numerical solvers. The library is written in C++ and it benefits from template meta–programming techniques. In this paper, we present the most important data structures and algorithms in TNL together with scalability on multi–core CPUs and speed–up on GPUs supporting CUDA

Guaranteed and robust a posteriori error estimates for singularly perturbed reaction-diffusion problems

International audienceWe derive a posteriori error estimates for singularly perturbed reaction-diffusion problems which yield a guaranteed upper bound on the discretization error and are fully and easily computable. Moreover, they are also locally efficient and robust in the sense that they represent local lower bounds for the actual error, up to a generic constant independent in particular of the reaction coefficient. We present our results in the framework of the vertex-centered finite volume method but their nature is general for any conforming method, like the piecewise linear finite element one. Our estimates are based on a H(div)-conforming reconstruction of the diffusive flux in the lowest-order Raviart-Thomas space linked with mesh dual to the original simplicial one, previously introduced by the last author in the pure diffusion case. They also rely on elaborated Poincaré, Friedrichs, and trace inequalities-based auxiliary estimates designed to cope optimally with the reaction dominance. In order to bring down the ratio of the estimated and actual overall energy error as close as possible to the optimal value of one, independently of the size of the reaction coefficient, we finally develop the ideas of local minimizations of the estimators by local modifications of the reconstructed diffusive flux. The numerical experiments presented confirm the guaranteed upper bound, robustness, and excellent efficiency of the derived estimates

COMPUTATIONAL METHODOLOGY TO ANALYZE THE EFFECT OF MASS TRANSFER RATE ON ATTENUATION OF LEAKED CARBON DIOXIDE IN SHALLOW AQUIFERS

Exsolution and re-dissolution of CO2 gas within heterogeneous porous media are investigated using experimental data and mathematical modeling. In a set of bench-scale experiments, water saturated with CO2 under a given pressure is injected into a 2-D water-saturated porous media system, causing CO2 gas to exsolve and migrate upwards. A layer of fine sand mimicking a heterogeneity within a shallow aquifer is present in the tank to study accumulation and trapping of exsolved CO2. Then, clean water is injected into the system and the accumulated CO2 dissolves back into the flowing water. Simulated exsolution and dissolution mass transfer processes are studied using both nearequilibrium and kinetic approaches and compared to experimental data under conditions that do and do not include lateral background water flow. The mathematical model is based on the mixed hybrid finite element method that allows for accurate simulation of both advection- and diffusion- dominated processes

Mixed-hybrid finite element method for modelling two-phase flow in porous media

We propose a new numerical scheme for simulation of flow of two immiscible and incompressible phases in porous media. The method is based on a combination of the mixedhybrid finite element (MHFE) and discontinuous Galerkin (DG) methods. The combined approach allows for accurate approximation of the flux at the boundary between neighboring finite elements, especially in heterogeneous media. We extend the method proposed in [12] to simulate the nonwetting phase pooling at material interfaces. In order to show its applicability, the MHFE-DG method is tested against benchmark solutions and using laboratory data from literature.MI: Global COE Program Education-and-Research Hub for Mathematics-for-IndustryグローバルCOEプログラム「マス･フォア･インダストリ教育研究拠点

Mixed-hybrid finite element method for modelling two-phase flow in porous media

MI: Global COE Program Education-and-Research Hub for Mathematics-for-IndustryグローバルCOEプログラム「マス･フォア･インダストリ教育研究拠点」We propose a new numerical scheme for simulation of flow of two immiscible and incompressible phases in porous media. The method is based on a combination of the mixedhybrid finite element (MHFE) and discontinuous Galerkin (DG) methods. The combined approach allows for accurate approximation of the flux at the boundary between neighboring finite elements, especially in heterogeneous media. We extend the method proposed in [12] to simulate the nonwetting phase pooling at material interfaces. In order to show its applicability, the MHFE-DG method is tested against benchmark solutions and using laboratory data from literature

Computable a posteriori error estimates in the finite element method based on its local conservativity: improvements using local minimization

We investigate in this paper improvements of the a posteriori error estimates in the finite element method discretization of the Poisson equation, introduced in [M. Vohralík, A posteriori error estimation in the conforming finite element method based on its local conservativity and using local minimization, C. R. Math. Acad. Sci. Paris 346 (2008), 687–690] and [M. Vohralík, Guaranteed and fully robust a posteriori error estimates for conforming discretizations of diffusion problems with discontinuous coefficients, submitted]. The estimates presented in these references are guaranteed in the sense that they feature no undetermined constants and fully computable but numerical experiments show that the effectivity index, i.e., the ratio of the estimated and actual error, does not approach the optimal value of one but rather a slightly bigger value. We identify in this paper the reason for this and introduce a possible remedy, which consists in performing a local minimization of the values of the estimators over patches of simplicial submesh elements. We then present a set of numerical experiments showing the improvements achieved and compare our estimators, both theoretically and numerically, with the classical residual ones