Alain Bastide

University of La Réunion · Laboratory of Physics and Mathematical Engineering for Energy and the Environment (PIMENT)

Several engineering problems result in a PDE-constrained optimization problem that aims at finding the shape of a solid inside a fluid which minimizes a given cost function. These problems are categorized as Topology Optimization (TO) problems. In order to tackle these problems, the solid may be located with a penalization term added in the constra...

Anaerobic digestion is a widely used process for waste treatment and energy production. This natural process takes place in a controlled environment, anaerobic digesters. Mixing is one of the main operating parameters. The understanding of the flows during the agitation of the medium is crucial for the optimization of the process yield. In fact, th...

A Topology Optimization (TO) problem is a PDE-constrained optimization problem that aims at finding the shape of a solid inside a fluid which minimizes a given cost function. The solid is located with a penalization term added in the constraints equations that vanishes in fluid regions and becomes large in solid regions. This paper addresses a TO p...

This paper deals with the finite element approximation of the Darcy-Brinkman-Forchheimer equation, involving a porous media with spatially-varying porosity, with mixed boundary condition such as inhomogeneous Dirichlet and traction boundary conditions. We first prove that the considered problem has a unique solution if the source terms are small en...

The objective of this study is to highlight the effect of porosity variation in a topology optimization process in the field of fluid dynamics. Usually a penalization term added to momentum equation provides to get material distribution. Every time material is added inside the computational domain, there is creation of new fluid-solid interfaces an...

This paper deals with a multi-objective topology optimization problem in an asymmetrically heated channel, based on both pressure drop minimization and heat transfer maximization. The problem is modeled by assuming steady-state laminar natural convection flow. The incompressible Navier-Stokes equations coupled with the convection-diffusion equation...

Topology optimization for fluid flow aims at finding the location of a porous medium minimizing a cost functional under constraints given by the Navier-Stokes equations. The location of the porous media is usually taken into account by adding a penalization term α u , where α is a kinematic viscosity divided by a permeability and u is the velocity...

The study’s ultimate goal consists of modelling and optimising the co-digestion of particulate substrates like sewage sludge, biowaste and vinasse from sugar cane. Given these substrates, the medium is highly heterogeneous and has particular physical characteristics and behaviour. Moreover, anaerobic digestion could be lead in wet-mode or in dry-mo...

This paper proposes a new interpolation technique based on density approach to solve topology optimization problems for heat transfer. Problems are modeled under the assumptions of steady-state laminar flow using the incompressible Navier-Stokes equations coupled to the convection-diffusion equation through the Boussinesq approximation. The governi...

This article consists in a numerical study of the influence of thermal stratification and surface radiation on laminar airflow induced by natural convection in vertical, asymmetrically heated channels. Several cases are investigated to spotlight their influence on fluid dynamics and thermal quantities. Thermal stratification is obtained by a weak g...

In tropical context and particularly in Reunion Island, promoting passive design is compulsory, but cannot be achieved without considering fire safety. This article aims at evaluating the interactions that exist between fire safety and thermal comfort in buildings, using variance based and moment independent methods. Two stategies are proposed: a f...

Dans les régions tropicales insulaires, la ventilation naturelle est fortement privilégiée, conseillée pour éviter le recours à des systèmes actifs de traitement d’air tels que les climatiseurs. Le but est de réduire, sur un territoire contraint où l’énergie électrique coûte extrêmement cher à produire, la consommation d’énergie primaire tout en fa...

RESUME. La vitesse d'air est un des critères de confort thermique de l'usager des bâtiments. Ainsi, une augmentation de la vitesse d'air sur l'usager contribue à la réduction de la température ressentie. Par conséquent, l'augmentation des mouvements d'air dans les zones de présence des usagers contribue alors à l'amélioration du confort thermique....

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Les quantités thermiques n'évoluent pas quelle que soit la configuration choisie. Seules les quantités thermiques dépendant des débits sont les seules influencées (,). Qve = V(X, 0)dX 0 1 ! Qvs = V(X, A)dX 0 1 ! Ges = V(X, A) ! V(X, A) 2 dX dw Les débits en entrée et sortie du canal sont diminués de presque 70% lorsque l'on impose un gradient de te...

The aim of this report is to present a model of a rigid-rotor system based on computational fluid dynamics (CFD), which is applied on a vertical axis wind turbine (VAWT) research. Its originality results from the use of the average value of the variable rotational speed method taken in a periodic steady-state (PSS) of the VAWT rotor instead of the...

The aim of the restoration of a building is to reduce energy cost and to improve indoor air quality. An important part of the energy cost of ventilation systems is due to a loss of power in ventilation duct. The goal of reducing energy costs is limitied by space and financial obligation. The flow can be passively controlled by adjusting the shape of...

Comparison exercises have been carried out by different research teams to study the sensitivity of the natural convection occurring in a vertical asymmetrically heated channel to four sets of open boundary conditions. The dimensionless parameters have been chosen so that a return flow exists at the outlet. On the whole, results provided by the part...

The present paper is concerned with the results of the numerical investigation of unsteady laminar, natural convection in an asymmetrically heated inclined open channel (i = 0, 45, 60 and 75°) with walls at uniform heat flux (qw = 10, 50, 75 and 100W ·m-2). Two methodological approaches have been adopted to investigate the air flow in this case: 2D...

This paper presents the coupling of a building thermal simulation code with genetic algorithms (GAs). GAs are randomized search algorithms that are based on the mechanisms of natural selection and genetics. We show that this coupling allows the location of defective sub-models of a building thermal model, i.e. parts of model that are responsible fo...

In order to provide comfort in a low energy consumption building, it is preferable to use natural ventilation rather than HVAC systems. To achieve this, engineers need tools that predict the heat and mass transfer between the building's interior and exterior. This paper presents a method implemented in some building software, and the results are co...

A bioclimatic approach to designing comfortable buildings in hot and humid tropical regions requires, firstly, some preliminary, important work on the building envelope to limit the energy contributions, and secondly, an airflow optimization of the building. For the first step, tools such as nodal or zonal models have been largely implemented. For...

Solar cooling applied to buildings is without a doubt an interesting alternative for reducing energy consumption in traditional mechanical steam compression air conditioning systems. The study of these systems should have a closely purely fundamental approach including the development of numerical models in order to predict the overall installation...

In detailled buiding simulation models, airflow modelling and solving are still open and crucial problems, specially in the case of open buildings as encountered in tropical climates. As a consequence, wind speed conditioning indoor thermal comfort or energy needs in case of air conditionning are uneasy to predict. A first part of the problem is th...

This article presents the CODYRUN software developped by University of La R\'eunion. It is a multizone thermal software, with detailled airflow and humidity transfer calculations. One of its specific aspects is that it constitutes a research tool, a design tool used by the lab and professionnals and also a teaching tool. After a presentation of the...

A bioclimatic approach to designing comfortable buildings in hot and humid tropical regions requires, firstly, some preliminary, important work on the building envelope to limit the energy contributions, and secondly, an airflow optimization of the building. For the first step, tools such as nodal or zonal models have been largely implemented. For...

L'objectif des simulations est d'apporter un appui technique à l'équipe de maîtrise d'œuvre du projet pour l'optimisation du confort hygro-thermique et des consommations énergétiques. Les simulations seront effectuées sur les zones de l'Administration et du bâtiment central avec le logiciel CODYRUN et pour deux périodes de l'année (été et hiver). E...

Le benchmark porte sur un problème de ventilation nocturne uniquement due à la convection naturelle. Le principe du travail est de comparer diverses méthodes utilisées dans le domaine du bâtiment pour évaluer les flux d'air et de chaleur. Le problème a donc été résolu par divers modèles adaptés, avec des méthodes allant des formules analytiques aux...

Une étude numérique de la ventilation naturelle d'un canal incliné est proposée, visant une comparaison résultats numériques et expérimentaux et analysant les écarts observés. Cet article se base sur une expérimentation existante au sein du Groupe de Recherche sur les Énergies Renouvelables (GRER Université des Antilles et de la Guyane). Les résult...

Le benchmark porte sur un problème de ventilation nocturne induite par convection naturelle. Ce problème est résolu ici par divers modèles adaptés au bâtiment, avec des méthodes allant des formules analytiques aux simulations numériques directes en passant par les modèles nodaux, zonaux, ou sous-résolus. L'accord entre toutes ces méthodes apparaît...

The Savonious rotor is a slow running vertical axis wind turbine (VAWT) which gets stabilized after a certain period of functioning. This work aims to assess the results of an aerodynamic study concerning a Savonious rotor. The computational fluid dynamics (CFD) is a technique used to solve the airflow around the wind turbine rotor. In this paper,...

Since naturally ventilated buildings respond to site conditions and microclimate, we cannot establish a “one set of criteria” for every naturally ventilated building. So natural ventilation should be optimized to deal with thermal comfort in passive buildings during summer. A survey of existing tools for natural ventilation simulation shows the dom...

This paper presents a numerical investigation of airflow in an open geometry. The case under consideration is a room with two opposite and decentred openings which create a strong potential for ventilation. The building's characteristic dimensions are the following: H=2.50 m height and W=6.50 m width. A temperature difference between the walls and...

This work deals with a different use of sensitivity analysis to characterize the steady-state behavior of solar collectors and more specifically evacuated tube collectors, which are often used for solar cooling. First, a dynamic model of evacuated tube collector (ETC) is presented. Then, a sensitivity analysis based on a spectral analysis (FAST met...

Cet article présente une étude numérique bidimensionnelle sur les écoulements d’air naturel, à l’intérieur d’une géométrie ouverte. La géométrie est un bâtiment (H = 2,50 m, L = 6,50 m) avec deux ouvertures opposées et décentrées permettant de créer une circulation d’air traversante. Une différence de températures entre les murs et l’air extérieur...

This study reports the flow physics past a Savonious wind turbine rotor. It is based on the modeling and numerical simulation of a VAWT experiments. The computational fluid dynamics (CFD) techniques was used with a rigid-rotor system to model the coupling. The SST k-ω model is the turbulence model taken into account in this dynamic study of a Savon...

Since naturally ventilated buildings respond to site conditions and microclimate, there is no "one set of spe- cific criteria" for every naturally ventilated building. So natural ventilation should be optimized to deal with ther- mal comfort in passive buildings during hot season. For this aim, we will propose a new method to reduce the number of i...

Solar cooling systems are unmistakably an interesting alternative to solve electric consumption problems of air conditioning systems working with mechanical vapour compression. The optimization program of solar cooling systems (ORASOL) managed by the national research agency (ANR) was created to propose a fundamental reflection, with the elaboratio...

Summer air conditioning represents a growing market in commercial and residential buildings. Solar energy is a very interesting energy source because of its advantages. Instead of a compressor system, which uses electricity, an absorption cooling system needs only heat produced by a solar collector plant. Furthermore, Reunion Island has a high sola...

The paper deals with a French national project named ENERPOS which involves three research laboratories and two design practices. The project concerns the development of new methods for the design of zero net energy buildings in French tropical overseas departments under hot summer conditions. This new approach will rely on the use of new dynamic s...

This paper presents a zero energy project -ie ZEN applied to a university building in Reunion Island. The construction work will begin in September 2006 and will last one year. The aim is to create a building which uses half the energy of a standard building. The methodology was conceived to meet requirements defined during the thermal design and b...

A simplified model of indoor short wave couplings adapted to multizone simulation context is proposed, thanks to some simplified hypothesis and the introduction of an indoor short wave exchange matrix. Through specific properties of this matrix, it appears as a useful step to quantify exchanges between zones separated by windows or large openings....

A bioclimatic approach to designing comfortable buildings in hot and humid tropical regions requires, firstly, some preliminary, important work on the building envelope to limit the energy contributions, and secondly, an airflow optimization of the building. For the first step, tools such as nodal or zonal models have been largely implemented. For...

In this paper, emphasis is put on the design of a neural network to model the direct solar irradiance. Since unfortunately a neural network (NN) is not a statistician in-a-box, building a NN for a particular problem is a non trivial task. As a consequence, we argue that in order to properly model the direct solar irradiance, a systematic methodolog...

Ce papier présente un projet de bâtiment universitaire à énergie positive à l’Ile de La Réunion. L’objectif est de réaliser un bâtiment consommant deux fois moins d’énergie qu’un bâtiment standard. La méthodologie a porté sur des exigences définies dès la phase programme sur la conception thermique et les systèmes. Les innovations portant sur la co...

Actes disposibles, http://www.esim.ca/2006

The aim of this paper is to show the influence of the atmospheric boundary layer profile on the distribution of velocity in a building having two large openings. The knowledge of the flow form inside a building is useful to define a thermal environment favourable with thermal comfort and good air quality. In computational fluid dynamics, several pr...

Controlling humidity to prevent moisture and condensation phenomena is a growing problem for building designers nowadays. Ventilation and air conditioning are common solutions to avoid mold and condensation. However, to promote low cost energy buildings, an alternate solution may be to decrease the daily variation of humidity with anti fungi treate...