Design of coupled finite volume schemes minimizing the grid orientation effect in reservoir simulation

In this paper, we propose an analysis method for the so-called grid orientation effect (GOE) in the numerical simulation of two-phase flows in porous media. The GOE, which occurs when using coupled finite volume schemes on structured grids, is well known to engineers. Several attempts, most of which are of empirical nature, have been put forward in order to alleviate this undesirable phenomenon. Here, our approach relies on a more rigorous notion of angular error for all directions, which in turn enables us via integration and minimization to single out the least anisotropic scheme within a given family of schemes depending on some tuning parameter(s). Numerical test problems testify to the improvement brought by the new construction. grid orientation effect; reservoir simulation; finite volume schemes; nine-point scheme

ECON: a Kernel Basis Pursuit Algorithm with Automatic Feature Parameter Tuning, and its Application to Photometric Solids Approximation

International audienceThis paper introduces a new algorithm, namely the Equi-Correlation Network (ECON), to perform supervised classification, and regression. ECON is a kernelized LARS-like algorithm, by which we mean that ECON uses an $l_1$ regularization to produce sparse estimators, ECON efficiently rides the regularization path to obtain the estimator associated to any regularization constant values, and ECON represents the data by way of features induced by a feature function. The originality of ECON is that it automatically tunes the parameters of the features while riding the regularization path. So, ECON has the unique ability to produce optimally tuned features for each value of the constant of regularization. We illustrate the remarkable experimental performance of ECON on standard benchmark datasets; we also present a novel application of machine learning in the field of computer graphics, namely the approximation of photometric solids

Worldwide trends in underweight and obesity from 1990 to 2022: a pooled analysis of 3663 population-representative studies with 222 million children, adolescents, and adults

Background Underweight and obesity are associated with adverse health outcomes throughout the life course. We estimated the individual and combined prevalence of underweight or thinness and obesity, and their changes, from 1990 to 2022 for adults and school-aged children and adolescents in 200 countries and territories. Methods We used data from 3663 population-based studies with 222 million participants that measured height and weight in representative samples of the general population. We used a Bayesian hierarchical model to estimate trends in the prevalence of different BMI categories, separately for adults (age ≥20 years) and school-aged children and adolescents (age 5–19 years), from 1990 to 2022 for 200 countries and territories. For adults, we report the individual and combined prevalence of underweight (BMI <18·5 kg/m2) and obesity (BMI ≥30 kg/m2). For schoolaged children and adolescents, we report thinness (BMI <2 SD below the median of the WHO growth reference) and obesity (BMI >2 SD above the median). Findings From 1990 to 2022, the combined prevalence of underweight and obesity in adults decreased in 11 countries (6%) for women and 17 (9%) for men with a posterior probability of at least 0·80 that the observed changes were true decreases. The combined prevalence increased in 162 countries (81%) for women and 140 countries (70%) for men with a posterior probability of at least 0·80. In 2022, the combined prevalence of underweight and obesity was highest in island nations in the Caribbean and Polynesia and Micronesia, and countries in the Middle East and north Africa. Obesity prevalence was higher than underweight with posterior probability of at least 0·80 in 177 countries (89%) for women and 145 (73%) for men in 2022, whereas the converse was true in 16 countries (8%) for women, and 39 (20%) for men. From 1990 to 2022, the combined prevalence of thinness and obesity decreased among girls in five countries (3%) and among boys in 15 countries (8%) with a posterior probability of at least 0·80, and increased among girls in 140 countries (70%) and boys in 137 countries (69%) with a posterior probability of at least 0·80. The countries with highest combined prevalence of thinness and obesity in school-aged children and adolescents in 2022 were in Polynesia and Micronesia and the Caribbean for both sexes, and Chile and Qatar for boys. Combined prevalence was also high in some countries in south Asia, such as India and Pakistan, where thinness remained prevalent despite having declined. In 2022, obesity in school-aged children and adolescents was more prevalent than thinness with a posterior probability of at least 0·80 among girls in 133 countries (67%) and boys in 125 countries (63%), whereas the converse was true in 35 countries (18%) and 42 countries (21%), respectively. In almost all countries for both adults and school-aged children and adolescents, the increases in double burden were driven by increases in obesity, and decreases in double burden by declining underweight or thinness. Interpretation The combined burden of underweight and obesity has increased in most countries, driven by an increase in obesity, while underweight and thinness remain prevalent in south Asia and parts of Africa. A healthy nutrition transition that enhances access to nutritious foods is needed to address the remaining burden of underweight while curbing and reversing the increase in obesit

Modélisation et calcul du tansfert de masse et de chaleur dans un milieu poreux réactif en évolution structurale et applications

L’objectif de ce travail est de développer un modèle et des techniques d’approximation numérique pour le transfert de masse et de chaleur dans un milieu poreux réactif en évolution structurale. Le modèle est obtenu par un changement d’échelle utilisant une technique d’homogénéisation d’une équation cinétique couplée à une équation de conduction thermique. Il permet de prendre en compte une large gamme de régimes pour le gaz allant d’un écoulement continu à un écoulement raréfié. L’approche est validée par de nombreuses comparaisons numériques, en particulier vis-à-vis de données expérimentales et met en évidence le caractère tensoriel des différents phénomènes de transport et leur évolution suivant le régime de l’écoulement. L’application de ces modèles, en particulier à l’étude de protections thermiques est présentée.The goal of this work is to derive a model and techniques of numerical approximation for heat and mass transfer in reactive porous media with structural evolution. The model is obtained by a scaling using a technique of homogenization of a kinetic equation coupled to an equation of thermal conduction. It is able to treat various physical regimes for the gas, from a continuous flow to a rarefied flow. The approach is validated by several numerical comparisons, in particular with respect to experimental data and shows the tensorial character of the various phenomena of transport and their evolution according to the regime of the flow. The application of these models, in particular to the study of thermal protection systems is present

About the Use of Quality Indicators to Reduce Information Loss When Performing Upscaling

Hydrocarbon reservoirs are characterized by the spatial distributions of petrophysical properties. These spatial characteristics are usually derived from well data and seismic information. To study a reservoir, the engineers build a fine geological model, also called a geostatistical model, to represent the field. The purpose is to capture as well as possible the peculiarities and heterogeneity of the true reservoir. At this stage, performing a flow simulation with such detailed geological models is just too time-demanding. Therefore, a possibility consists of upscaling the geological model to an upscaled mesh, thus resulting in a coarse reservoir model for which fluid flow can be numerically simulated in a reasonable amount of time. The coarse grid blocks of this reservoir model are attributed equivalent petrophysical properties related to the properties populating the fine grid blocks. These properties are upscaled, and so they do not capture all of the details of the fine model. In this paper, we investigate the potential of various numerical and easy to compute criteria, which help evaluate the information loss due to the upscaling process. Our final purpose is to provide and access the reliability of quality indicators, which make it possible to evaluate the quality of the upscaled reservoir model. The potential of this systematic and integrated study is illustrated with two types of numerical experiments based upon the SPE10 case. First, we apply different upscaling methods to determine coarse reservoir models. Quality indicators are computed for each of them so that we identify the most suitable upscaling methods. Then, the upscaled models are input to flow simulators to check the accuracy of our quality estimations. Second, we also investigate the influence of coarsening and try to determine from the computed quality indicators the coarse cell size above which too much information is lost

Modélisation et calcul du transfert de masse et de chaleur dans un milieu poreux réactif en évolution structurale et applications

L'objectif de ce travail est de développer un modèle et des techniques d'approximation numérique pour le transfert de masse et de chaleur dans un milieu poreux réactif en évolution structurale. Le modèle obtenu par un changement d'échelle utilisant une technique d'homogénéisation d'une équation cinétique couplée à une équation de conduction thermique. Il permet de prendre en compte une large gamme de régimes pour le gaz allant d'un écoulement continu à un écoulement rarefié. L'approche est validée par de nombreuses comparaisons numériques, en particulier vis-à-vis de données expérimentales et met en évidence la caractère tensoriel des différents phénomènes de transport et leur évolution suivant le régime de l'écoulement. L'application de ces modèles en particulier à l'étude de protections thermiques est présentée.BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Computation of effective transport coefficients of a microscale gas flow

International audienc