Vers une approche locale-globale de la rupture en interaction fluide structure

Le contexte de ce travail est celui de la prédiction de la tenue de structures complexes au moyen de modèles matériaux fins comme ceux utilisés par exemple pour les structures composites. Jusqu'ici le LMT-Cachan a travaillé sur des chargements imposés donnés et développé des méthodes ad hoc et notamment sur l'adaptation d'une stratégie multiéchelle avec homogénéisation. Dans le cadre de problèmes d'interaction fluide structure jusqu'à rupture la question posée est celle de l'adaptation de ce type de méthode. Ce travail exploratoire est une première tentative dans ce sens

La simulation des flux radiatifs en milieu urbain : comparaison de stratégies

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A mixed, scalable domain decomposition method for incompressible flow

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Noise source identification with the lattice Boltzmann method

International audienceIn this paper the sound source identification problem is addressed with the use of the lattice Boltzmann method. To this aim, a time-reversed problem coupled to a complex differentiation method is used. In order to circumvent the inherent instability of the time-reversed lattice Boltzmann scheme, a method based on a split of the lattice Boltzmann equation into a mean and a perturbation component is used. Lattice Boltzmann method formulation around an arbitrary base flow is recalled and specific applications to acoustics are presented. The implementation of the noise source detection method for two-dimensional weakly compressible (low Mach number) flows is discussed, and the applicability of the method is demonstrated

Extension of the LATIN framework for multi-scale computation of fluid-structure interaction

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Evaluation of directional quadrature schemes for simulating urban radiative transfer using the Discrete Ordinate Method

International audienceIn the last decades, different numerical methods have been applied to simulate radiative transfer in urban configurations. In cases where atmospheric air is treated as an absorbing gas, it has been shown in many cases that the use of the Discrete Ordinate Method has been shown in many situations to provide a good compromise between calculation cost and accuracy. In this paper, several quadrature schemes for directional integration in the DOM are compared for different urban conditions and types (visible, thermal infrared) of radiation. This allows for determining which angular quadrature scheme is the most appropriate for urban radiative transfer calculations. In conclusion, the Fibonacci quadrature set outperforms all other quadratures in the traditional canyon simulation with a transparent model. Meanwhile, the performance of Level Symmetric Odd and Hybrid quadrature (LSO/LSH) and Equal Weight Odd (EWO) catch up with Fibonacci's in a participative atmosphere model

Impact of spectral coupling between urban atmosphere and sky boundary conditions in a street canyon

International audienceMost radiative transfer models developed for the analysis of urban configurations consider a transparent urban atmosphere and gray sky conditions. The aim of the present work is to investigate these assumptions, focusing on the longwave domain. For this purpose, reference Line-by-Line Monte-Carlo calculations are first performed. A more efficient radiative transfer model based on the Finite Volume Method and SLW modeling is also developed to treat several street canyon configurations. The aspect ratio of the street canyon, a parameter frequently encountered in urban scenarios, is considered for the analysis. It is shown that, in most cases, real urban problems need to take into account a non-gray participating atmosphere within the streets, together with its spectral coupling with the non-gray sky downward radiation, to provide accurate net fluxes on urban surfaces and volumetric radiative powers in the urban atmosphere

Nouvelle approche d'évaluation de potentiels de ressources bioclimatiques en climat chaud et humide

International audienceSpécificité d'une étude en climat chaud Base de la méthodologie Conclusion Application et synthèse des résultats Perspectives 40% 10% 25% 16% 9% Consommation d'électricité par usage – Djibouti, 2013 Climatisation Eclairage Brasseur d'air Regrigerateur Autre Electromenagers 2 3 4 5 6 Cette étude propose une nouvelle définition de potentiels d'utilisation de ressources bioclimatiques adaptée au climat chaud et humide et permettant le rafraichissement des bâtiments. Dans le contexte du climat chaud, le principal défi à relever est celui de la climatisation. A ce défi s'ajoutent deux problèmes majeurs: L'inadaptation des techniques de construction, Le manque des travaux sur les ressources énergétiques disponibles, 5 10 15 20 25 30 35 40 0 30 60 90 120 150 180 210 240 270 300 330 360 Température de l'air [°C] Température du ciel [°C] Jours Température [°C] 30 32 34 36 38 40 42 44 0 40 80 120 160 200 240 280 320 360 T sol (0,t) T sol (0.5,t) T sol (2,t) T sol (3,t) T sol (4,t) Température du sol [°C

Complete Numerical Evaluation of the BIPV’s Production and Envelope Temperatures in Urban Areas.

In order to locally produce electricity in urban areas, it is important to properly assess the potential of the Buildings Integrated PhotoVoltaic (BIPV) technologies. Therefore, the evaluation of the incident solar radiative flux in dense urban areas, taking into account multiple reflections over all urban elements, is a current subject of interest. Although different models exist to evaluate the intensity of the power density on each zone of each part of an urban scene, the reflective properties of the different urban materials are generally simplified, and they are commonly supposed to reflect uniformly wavelength through the space. Henceforth, this brings up questions about the relevance of these assumptions and their influence in the numerical evaluation of the PhotoVoltaic (PV) potential. Thus, this paper reviews the different alternatives to proceed with a preliminary evaluation of the solar potential in dense urban areas, with the aim of evaluating the influence of the material reflection properties on the power density incident on a fac¸ade. Two models are discussed: one based on the radiosity method and the other based on the raytracing method. The construction of both methods is detailed and results for both models under similar hypothesis are compared. Moreover, the influence of different reflection properties is also studied

Identification of BRDF parameters with spectral measurements in the visible light spectrum towards solar irradiation evaluation in urban environment for photovoltaïc technologies

International audienceIn order to incorporate real construction material reflectance properties in a Monte-Carlo ray tracing algorithm, a representative cladding material is characterised with a spectrophotometer to obtain reflectance angular distribution. These measurements are used to design a BRDF model with a reduced number of parameters that are further identified, along with their confidence intervals. Obtained results are compared to reflectance coefficients measured with an integrating sphere. The prospects of such a model is to allow for a more accurate modelling of the optical properties of materials in reflection. This knowledge can then allow a better integration of photovoltaic technologies, both in terms of energy and visual acceptance. For the particular HPL cladding material tested and despite a highly specular behavior at grazing incidence angles, we found that the specular term only amounts to 4% of reflection