A coupling concept for Stokes-Darcy systems: The ICDD method

We present a coupling framework for Stokes-Darcy systems valid for arbitrary flow direction at low Reynolds numbers and for isotropic porous media. The proposed method is based on an overlapping domain decomposition concept to represent the transition region between the free-fluid and the porous-medium regimes. Matching conditions at the interfaces of the decomposition impose the continuity of velocity (on one interface) and pressure (on the other one) and the resulting algorithm can be easily implemented in a non-intrusive way. The numerical approximations of the fluid velocity and pressure obtained by the studied method converge to the corresponding counterparts computed by direct numerical simulation at the microscale, with convergence rates equal to suitable powers of the scale separation parameter ε in agreement with classical results in homogenization

Is minimising the convergence rate the best choice for efficient Optimized Schwarz preconditioning in heterogeneous coupling? The Stokes-Darcy case

Optimized Schwarz Methods (OSM) are domain decomposition techniques based on Robin-type interface condition that have became increasingly popular in the last two decades. Ensuring convergence also on non-overlapping decompositions, OSM are naturally advocated for the heterogeneous coupling of multi-physics problems. Classical approaches optimize the coefficients in the Robin condition by minimizing the effective convergence rate of the resulting iterative algorithm. However, when OSM are used as preconditioners for Krylov solvers of the resulting interface problem, such parameter optimization does not necessarily guarantee the fastest convergence. This drawback is already known for homogeneous decomposition, but in the case of heterogeneous decomposition, the poor performance of the classical optimization approach becomes utterly evident. In this paper, we highlight this drawback for the Stokes/Darcy problem and we propose a more effective alternative optimization procedure.European Union Seventh Framework Programme (FP7/2007-2013; grant 294229) to M. Discacciat

Optimized Schwarz Methods in the Stokes-Darcy Coupling

This article studies optimized Schwarz methods for the Stokes–Darcy problem. Robin transmission conditions are introduced, and the coupled problem is reduced to a suitable interface system that can be solved using Krylov methods. Practical strategies to compute optimal Robin coefficients are proposed, which take into account both the physical parameters of the problem and the mesh size. Numerical results show the effectiveness of our approach.European Union Seventh Framework Programme (FP7/2007-2013; grant 294229) to M. Discacciat

PSEUDOSPECTRAL LEAST SQUARES METHOD FOR STOKES-DARCY EQUATIONS

We investigate the first order system least squares Legendre and Chebyshev pseudospectral method for coupled Stokes-Darcy equations. A least squares functional is defined by summing up the weighted L-2-norm of residuals of the first order system for coupled Stokes-Darcy equations and that of Beavers-Joseph-Saffman interface conditions. Continuous and discrete homogeneous functionals are shown to be equivalent to a combination of weighted H(div) and H-1-norms for Stokes and Darcy equations. The spectral convergence for the Legendre and Chebyshev methods is derived. Some numerical experiments are demonstrated to validate our analysisopen0

Augmented Interface Systems for the Darcy-Stokes Problem

In this paper we study interface equations associated to the Darcy-Stokes problem using the classical Steklov-Poincaré approach and a new one called augmented. We compare these two families of methods and characterize at the discrete level suitable preconditioners with additive and multiplicative structures. Finally, we present some numerical results to assess their behavior in presence of small physical parameters

Riesgo de caries, en relación a placa bacteriana, observado en una población de niños que ingresan a la Escuela Primaria

La placa bacteriana, es un factor de riesgo biológico importante en la morbilidad dentaria. La edad cronológica-psico-emocional del niño que inicia la escuela primaria, es interesante para valorar circunstancias que hacen posible la presencia y actuación de dicho factor, considerando aspectos asociados (hábitos y costumbres) con los que ingresa a la escuela. El objetivo fue identificar la situación de riesgo de caries, en relación al facto r  placa bacteriana, evaluando su prevalencia y  la presencia del hábito hogareño de eliminarla. El estudio se realizó en dos escuelas de la ciudad de Corrientes, seleccionando al azar 200 niños in­gresantes al l°Año de la EGBI. Se evaluó la presencia de placa por medio del índice de O'Leary y el hábito de cepillarse los dientes, a través de una encuesta. Resultados: El índice de O'Leary fue 65%, indicando un nivel de Alto Riesgo. Sólo el 7% de los niños, presentó valores compatibles con Salud. El 55%, se cepillaban los dientes, realizando solos la práctica, en el 85% de los casos. Conclusiones: Los niños que ingresan a la escuela primaria, presentan alto riesgo de enfermar de caries. Es necesario implementar acciones para disminuir el riesgo, contribuyendo a la salud de los dientes permanentes a erupcionar

Note sur la présence d'aflatoxine dans les fanes d'arachides

Les fanes d'arachide constituent en pays arachidien et spécialement au Sénégal un aliment appété par les diverses espèces animales. Des recherches effectuées sur ce fourrage au Laboratoire National de l'Elevage et de Recherches Vétérinaires de Dakar, ont révélé la présence d'aflatoxine de toxicité comparable à celle trouvée dans la graine et les tourteaux d'arachid

Note préliminaire sur les effets expérimentaux de l'aflatoxine chez les bovins tropicaux. Effets de l'aflatoxine sur la vache laitière et sur le jeune nourri à la mamelle

Cette première expérimentation se situe dans le cadre d'un programme à long terme sur les effets de l'aflatoxine chez les bovins tropicaux. Elle a pour but de rechercher chez la vache en lactation, recevant une dose expérimentale volontairement forte de 1,5 mg d'aflatoxine par jour, les désordres susceptibles d'être produits, chez la mère et chez le jeune. Alors que les adultes semblent résister à l'intoxication, les répercussions sont plus sensibles chez le jeune qui accuse un retard de croissance significatif. Les troubles observés chez les veaux à la mamelle paraissent liés à la présence d'aflatoxine dans le lai