1,666 research outputs found
Formal upscaling and numerical validation of unsaturated flow models in fractured porous media
No full textIn this work, we consider a mathematical model for describing flow in an unsaturated porous medium containing a fracture. Both the flow in the fracture as well as in the matrix blocks are governed by Richards' equation coupled by natural transmission conditions. Using formal asymptotics, we derive upscaled models as the limit of vanishing ε, the ratio of the width and length of the fracture. Our results show that the ratio of porosities and permeabilities in the fracture to matrix determine, to the leading order of approximation, the appropriate effective model. In these models the fracture is a lower dimensional object for which different transversally averaged models are derived depending on the ratio of the porosities and permeabilities of the fracture and respective matrix blocks. We obtain a catalogue of effective models which are validated by numerical computations.Acknowledgements
The work of K. Kumar and F. A. Radu was partially supported by the Research Council of Norway through the projects Lab2Field no. 811716, IMMENS no. 255426, CHI no. 25510, MICAP no. 811696 and Norwegian Academy of Science and
Statoil through VISTA AdaSim no. 6367. I. S. Pop was supported by the Research Foundation-Flanders (FWO) through the Odysseus programme (project GOG1316N), the project G051418N, and by Statoil through the Akademia agreement
Iterative schemes for surfactant transport in porous media
No full textIn this work, we consider the transport of a surfactant in variably saturated porous media. The water flow is modelled by the Richards equations and it is fully coupled with the transport equation for the surfactant. Three linearization techniques are discussed: the Newton method, the modified Picard, and the L-scheme. Based on these, monolithic and splitting schemes are proposed and their convergence is analyzed. The performance of these schemes is illustrated on five numerical examples. For these examples, the number of iterations and the condition numbers of the linear systems emerging in each iteration are presented.publishedVersio
Numerical solvers for a poromechanic problem with a moving boundary
No full textWe study a poromechanic problem in presence of a moving boundary. The poroelastic material is described by means of the Biot model while the moving boundary accounts for the effect of surface erosion of the material. We focus on the numerical approximation of the problem, in the framework of the finite element method. To avoid re-meshing along with the evolution of the boundary, we adopt the cut finite element approach. The main issue of this strategy consists of the ill-conditioning of the finite element matrices in presence of cut elements of small size. We show, by means of numerical experiments and theory, that this issue significantly decreases the performance of the numerical solver. For this reason, we propose a strategy that allows to overcome the ill-conditioned behavior of the discrete problem. The resulting solver is based on the fixed stress approach, used to iteratively decompose the Biot equations, combined with the ghost penalty stabilization and preconditioning applied to the pressure and displacement sub-problems respectively
Numerical homogenization of non-linear parabolic problems on adaptive meshes
No full textWe propose an efficient numerical strategy for solving non-linear parabolic problems defined in a heterogeneous porous medium. This scheme is based on the classical homogenization theory and uses a locally mass-conservative formulation at different scales. In addition, we discuss some properties of the proposed non-linear solvers and use an error indicator to perform a local mesh refinement. The main idea is to compute the effective parameters in such a way that the computational complexity is reduced but preserving the accuracy. We illustrate the behavior of the homogenization scheme and of the non-linear solvers by performing two numerical tests. We consider both a quasi-periodic example and a problem involving strong heterogeneities in a non-periodic medium.The authors gratefully acknowledge financial support from the Research Foundation - Flanders (FWO) through the Odysseus programme (Project G0G1316N). In addition, we wish to thank Professor Mary F. Wheeler and Professor Ivan Yotov who made valuable suggestions or who have otherwise contributed to the ideas behind this manuscript. Part of this work was elaborated during the stay of the first author at the University of Bergen, supported by the Research Foundation - Flanders (FWO), through a travel grant for a short stay abroad. We thank the referees for their valuable comments that helped improving this wor
Nonsteroidal anti-inflammatory drugs in clinical and experimental epilepsy
No full textCurrent antiepileptic drugs have limited efficacy and provide little or no benefits in 30% of the patients. Given that a role for brain inflammation in epilepsy has been repeatedly reported in recent years, the potential of anti-inflammatory drugs should be explored in depth, as they may provide new therapeutical approaches in preventing or reducing epileptogenesis. Here, we review preclinical (both in vivo and in vitro) and clinical epilepsy studies in which nonsteroidal antiinflammatory drugs (NSAIDs), i.e. cyclooxygenase-2 (COX-2) selective inhibitors (COXIBs) and nonselective NSAIDs, were used for seizure control. The effects of NSAIDs are reviewed in animal models of both chemical (pilocarpine, kainic acid, pentylenetetrazol, or carbachol administration) and electrical (tetanic hippocampal stimulation, electroshock) seizure induction. In the pilocarpine model, NSAIDs are neuroprotective, reduce mossy fiber sprouting or diminish P-glycoprotein upregulation, but only rarely protect against seizures. While neuroprotective effects have also been observed in the kainic acid model, NSAIDs tend in general to worsen seizure activity. Effects of COXIB administration in the pentylenetetrazol-induced seizures model are variable, alternating from protection against seizures to null effects or even increased incidence of convulsions. Moreover, NSAIDs tested in the tetanic hippocampal stimulation model diminished the seizure-associated P-glycoprotein upregulation, but were not very effective in seizure control. NSAIDs efficacy in experimental in vivo epilepsy studies may be influenced by multiple factors, including the timing of administration (before or after status epilepticus induction), the animal model of epilepsy or some of the signaling pathways involved in cyclooxygenase induction (e.g. prostaglandins and their receptors). On the other hand, the few clinical studies on the use of NSAIDs in neurological pathologies accompanied/characterized by seizures indicate that nonselective NSAIDs (e.g. aspirin) in prolonged, low-dose treatments may offer protection against seizures and stroke-like events. No clinical trials in epileptic patients using COXIBs have been conducted so far, as several international drug-control authorities have withdrawn these drugs from the market; future studies should focus on improved COXIB formulations. We argue that, while the available evidence is still inconclusive, the potential therapeutic benefits of controlling and diminishing brain inflammation in the treatment of epilepsy should be actively explored
Bulletin (Florin Japanese American Citizens League), no. 8 (May 16, 1942)
No full textNewsletter of the Florin chapter of the Japanese American Citizens League covering issues related to incarceration including an editorial by Mary Tsukamoto, news from Temporary Assembly Centers, care of pets, Japanese American soldiers, inoculation certificates, access to bank services, information about the Farm Security office, the Sacramento Workers Compensation Claims Administration, advice for incarcerees, work of the national Japanese American Citizens League, voting, verification papers, address changes, and recognition of individuals for their financial contributions. Newsletter labeled "Bulletin No. 8"The Japanese American Archival Collection documents the people, places, and daily life of Japanese Americans, primarily those who lived in the once thriving community of pre-war Florin in the Sacramento region, as well as the conditions in American incarceration camps during World War II. The approximately 7,000 original items include personal and official letters, photographs, diaries, arts and crafts, newsletters, textiles, camps artifacts, yearbooks and other publications
Bulletin (Florin Japanese American Citizens League), no. 9 (May 23, 1942)
No full textNewsletter of the Florin chapter of the Japanese American Citizens League covering issues related to evacuation including "Farewell" by Mary Tsukamoto, an editorial by John S. Hirohata, advice for evacuees, inoculation, want ads, social welfare, extra rice, access to bank services, recognition of volunteers and individuals for their financial contributions, information about the newsletter, care of pets, treasurers report, and information about control stations. Newsletter labeled "Bulletin No. 9."The Japanese American Archival Collection documents the people, places, and daily life of Japanese Americans, primarily those who lived in the once thriving community of pre-war Florin in the Sacramento region, as well as the conditions in American incarceration camps during World War II. The approximately 7,000 original items include personal and official letters, photographs, diaries, arts and crafts, newsletters, textiles, camps artifacts, yearbooks and other publications
Florin Chapter of Japanese American Citizens League newsletter, April 24, 1942
No full textNewsletter of the Florin chapter of the Japanese American Citizens League covering issues related to incarceration including storage of personal items, members trained in first aid, care of pets, and address changes. Also includes a memorial statement for Hiroyuki [Kato] and recognition of individuals for their financial contributions.The Japanese American Archival Collection documents the people, places, and daily life of Japanese Americans, primarily those who lived in the once thriving community of pre-war Florin in the Sacramento region, as well as the conditions in American incarceration camps during World War II. The approximately 7,000 original items include personal and official letters, photographs, diaries, arts and crafts, newsletters, textiles, camps artifacts, yearbooks and other publications
A Mixed Dimensional Model for the Interaction of a Well with a Poroelastic Material
No full textWe develop a mathematical model for the interaction of the mechanics of a three-dimensional permeable reservoir or aquifer with the flow through wells. We apply a model reduction technique that represents the wells as one-dimensional channels with arbitrary configuration in the space and we introduce proper coupling conditions to account for the interaction of the wells with the bulk region. The resulting problem consists of coupled partial differential equations defined on manifolds with heterogeneous dimensionality. To highlight the potential of this modeling approach in the description of realistic scenarios, we combine it with a suitable discretization method and we discuss the results of preliminary simulations on an idealized test case containing two wells
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