De nos, jours avec la démocratisation des équipements électroniques et l’explosions des services informatiques proposés sur le web, la consommation des datacenters devient un enjeu énergétique et économique majeur. Ce terme qui peut être traduit par « centre de calcul », désigne les infrastructures qui hébergent et font fonctionner en permanence des serveurs informatiques. Son rôle est de fournir aux équipements électroniques un environnement thermique adapté, ainsi qu’une alimentation électrique stable de manière à assurer une très grande sécurité de fonctionnement. Mais l’activité permanente des serveurs génère de grandes quantités de chaleurs, et un refroidissement permanent est nécessaire. Cette étude à pour objectif de mieux comprendre les phénomènes physiques qui interviennent dans le fonctionnement des datacenters afin d’apporter des solutions pour optimiser leur fonctionnement et diminuer leur consommation. A l’aide de simulations numériques, nous étudions les écoulements d’air et les transferts de chaleur qui interviennent dans la salle informatique, et nous proposons un nouveau modèle numérique qui permet de simuler le comportement des serveurs de nouvelle génération. Puis, grâce à une méthode de type POD, couplée au logiciel TRNSYS, nous développons un modèle « transversal » capable de simuler le fonctionnement complet d’un centre de calcul depuis les équipements informatiques, jusqu’au système de production d’air froid. Finalement, ce dernier est employé pour concevoir et tester un système de régulation adaptatif qui permet de réduire significativement les consommations d’énergie. / Nowadays, with the constant evolution of Information Technology (IT) equipments, the energy consumption of datacenter over the world becomes a major concern. These infrastructures are designed to provide an adapted thermal environment and an uninterrupted power supply to the IT servers, in order to guarantee a high level of reliability. However, the constant activity of electronic equipments releases a large amount of heat, and requires a constant cooling. Thus the objective of this work is to study the physical phenomena involved in an operating datacenter, in order to optimize the process and to reduce its energy consumption. Using numerical simulation, we study the air flow and the heat transfers happening in the servers’ room. To quantify the impact of new generation servers on the cooling process, we propose a numerical model that simulates the behavior of “blade” server. Then, using a Proper Orthogonal Decomposition (POD) method linked to the software TRNSYS, we propose a new “transversal” model, that simulates a datacenter behavior from the servers to the cooling plant. This model is used to develop a new adaptive regulation strategy, which constantly optimizes the system in order to ensure a safe thermal environment, and provides large energy savings.

The goal of this thesis is to design an attachment between a duct and a pod. A pod is what could be compared to an outboard engine for larger vessels. The pod is placed on the outside of the ship’s hull and can rotate 360 ̊. A duct is a large steel ring that can be placed around the propeller on the pod to increasethe propulsion force of the ship in lower velocities. The thesis is written for Rolls Royce AB in Kristinehamn.The demanded requirements of the design are: it must be easy to adapt to different sizes and shapes of pod houses, the duct must be able to bemounted and dismounted from the pod.The result from this thesis is that anupper and a lower attachment weredesigned. The upper attachment consists of two parallel steel plates which arebolted together with a screw plate that is welded to the pod house.The lower attachment is basically a wing with a streamlined profile which is bolted to a stay. Both attachments consist of bolted joints, two guide pins and bursting screws.The design is controlled by parameters in CAD, meaning that if you change the size of the duct the attachments automatically adapts themselves to the new dimensions.The total result from this thesis is a design suggestion and not an actual manufactured product.The design is dimensioned by a load analysis and strength calculations. The dimensions of the bolts are determined by basic load calculation and the guide pins aredimensioned to withstand the shear forces that occur.The conclusion of this thesis is that the developed attachment solution is a good way to solve this problem andthe personal recommendation is that it should be developed further.Further design work that needs to be done with the attachment is a more thorough analysis of the strength and especially with fatigue, since no account has been taken considering fatigue. / Målet med detta arbete är att konstruera en infästning mellan en dysa och en pod. En pod är vad som kan liknasen utombordsmotor för stora fartyg som sitter på utsidan av skrovet och kan rotera 360 ̊. En dysa är en stor stålring som kan sättas runt propellern, dysan ger förenklaten ökad framdrivningskraft och är lämplig för användning vid fartygstillämpningar där det handlar om låga hastigheter.Arbetet utförs på uppdrag av Rolls Royce AB i Kristinehamn.Kraven som ställdes på konstruktionen var att den skulle vara lätt att anpassa och att det skulle gå att montera och demontera dysan.Problemformuleringen för arbetet är att en ny infästning behövs för att kunna fästa dysan i poden.Resultatet av arbetet blev en övre och en nedre infästning på dysan. Den övre infästningen består av två parallella plåtar som skruvas ihop med en svetsad infästning på dysan. Den nedre infästningen består av en vinge med en strömningsvänlig profil som skruvas fast på ett stag. Båda infästningarna består av ett skruvförband, två styrpinnar och sprängskruv.Konstruktionen parametriserades i CAD så attomdysans storlekändrasså följer infästningarna med.Hela arbetet resulterade i ett konstruktionsförslag.Konstruktionen har dimensionerats med hjälp av en lastanalys och hållfasthetsberäkningarför att uppskatta infästningarnas nedböjning. Skruvförbanden har dimensionerats med enklare beräkningar och styrpinnarna har dimensioneratför att uppta skjuvspänningar.Slutsatsen som dras av arbetet är att konstruktionen är en lämplig lösning på problemet och rekommendationen är att det är värt att undersöka denna lösning vidare.Vidarearbete som behöver utföras är nogrannare dimensionering av konstruktionen, ingen hänsynhar tagits till utmattning eller vridning då det inte fanns tid inom arbetets tidsram för detta.

Nous nous intéressons dans ce mémoire à des méthodes de parallélisation par découplage du système dynamique. Plusieurs applications numériques de nos jours conduisent à des systèmes dynamiques de grande taille et nécessitent des méthodes de parallélisation en conséquence pour pouvoir être résolues sur les machines de calcul à plusieurs processeurs. Notre but est de trouver une méthode numérique à la fois consistante et stable pour réduire le temps de la résolution numérique. La première approche consiste à découpler le système dynamique en sous-systèmes contenant des sous-ensembles de variables indépendants et à remplacer les termes de couplage par l’extrapolation polynomiale. Une telle méthode a été introduite sous le nom de schéma C (p, q, j), nous améliorons ce schéma en introduisant la possibilité à utiliser des pas de temps adaptatifs. Cependant, notre étude montre que cette méthode de découplage ne peut satisfaire les propriétés numériques que sous des conditions très strictes et ne peut donc pas s’appliquer aux problèmes raides présentant des couplages forts entre les sous-systèmes. Afin de pouvoir répondre à cette problématique de découplage des systèmes fortement couplés, on introduit le deuxième axe de recherche, dont l’outil principal est la réduction d’ordre du modèle. L’idée est de remplacer le couplage entre les sous-ensembles de variables du système par leurs représentations sous forme réduite. Ces sous-systèmes peuvent être distribués sur une architecture de calcul parallèle. Notre analyse du schéma de découplage résultant nous conduit à définir un critère mathématique pour la mise à jour des bases réduites entre les sous-systèmes. La méthode de réduction d’ordre du modèle utilisée est fondée sur la décomposition orthogonale aux valeurs propres (POD). Cependant, ne disposant pas à priori des données requises pour la construction de la base réduite, nous proposons alors un algorithme de construction incrémentale de la base réduite permettant de représenter le maximum des dynamiques des solutions présentes dans l’intervalle de simulation. Nous avons appliqué la méthode proposée sur les différents systèmes dynamiques tels que l’exemple provenant d’une EDP et celui provenant de l’équation de Navier Stokes. La méthode proposée montre l’avantage de l’utilisation de l’algorithme de découplage basé sur la réduction d’ordre. Les solutions numériques sont obtenues avec une bonne précision comparées à celle obtenue par une méthode de résolution classique tout en restant très performante selon le nombre de sous-systèmes définis. / In this thesis, we are interested in parallelization algorithm for solving dynamical systems. Many industrial applications nowadays lead to large systems of huge number of variables. A such dynamical system requires parallel method in order to be solved on parallel computers. Our goal is to find a robust numerical method satisfying stability and consistency properties and suitable to be implemented in parallel machines. The first method developed in this thesis consists in decoupling dynamical system into independent subsystems and using polynomial extrapolation for coupled terms between subsystems. Such a method is called C(p; q; j).We have extended this numerical scheme to adaptive time steps. However, this method admits poor numerical properties and therefore cannot be applied in solving stiff systems with strong coupling terms.When dealing with systems whose variables are strongly coupled, contrary to the technique of using extrapolation for coupled terms, one may suggest to use reduced order models to replace those terms and solve separately each independent subsystems. Thus, we introduced the second approach consisting in using order reduction technique in decoupling dynamical systems. The order reduction method uses the Proper Orthogonal Decomposition. Therefore, when constructing reduced order models, we do not have all the solutions required for the POD basis, then we developed a technique of updating the POD during the simulation process. This method is applied successfully to solve different examples of dynamical systems : one example of stiff ODE provided from PDE and the other was the ODE system provided from the Nervier-Stokes equations. As a result, we have proposed a robust method of decoupling dynamical system based on reduced order technique. We have obtained good approximations to the reference solution with appropriated precision. Moreover, we obtained a great performance when solving the problem on parallel computers.

Dans cette thèse, nous nous sommes intéressés à l’étude mathématique de la sensibilité paramétrique de la méthode de réduction de modèles par projection connue sous le nom de POD pour Proper Orthogonal Decomposition. Dans beaucoup d’applications de la mécanique des fluides,la base de projection (base POD) calculée à un paramètre caractéristique fixe du problème de Navier-Stokes, est utilisée à la suite pour construire des modèles d’ordre réduit ROM-POD pour d’autres valeurs du paramètre caractéristique. Alors, la prédiction du comportement de ce ROM-POD vis-à-vis du problème initial est devenue cruciale. Pour cela, nous avons discuté cette problématique d’un point de vue mathématique. Nous avons établi des résultats mathématiques de sensibilité paramétrique des erreurs induites par application de la méthode ROM-POD. Plus précisément, notre approche est basée sur l’établissement d’estimations a priori de ces erreurs paramétriques, en utilisant les méthodes énergétiques classiques. Nos résultats sont démontrés pour les deux problèmes de type Burgers et Navier-Stokes. Des validations numériques de ces résultats mathématiques ont été faites uniquement pour le problème de type Burgers. / In this thesis, we are interested in the mathematical study of the parametric sensitivity of the reduced order model method known as the POD method (proper orthogonal decomposition). In several works applied to fluid mechanics, the POD modes are computed once and for all in association with a fixed parameter that characterize the equations of the fluid mechanics : Navier-Stokes system. Then, these modes are used in order to compute reduced order models (ROM) associated to these equations, for different parameter values. So, one needs a tool for predicting the behavior of the reduced order model with respect to the complete problem, when the parameter’s value is changing. We have discussed this problem from a mathematical point of vue. In fact, we have established mathematical results on the parametric sensitivity of the errors induced by applying the ROM-POD method. More precisely, our work is based on developing a priori estimations of these parametric errors, by using classical techniques of energy estimation.Our results are proved for the two problems of Burgers and Navier-Stokes. Numerical validations are established only in the case of the Burgers equation.

Segregation patterns of several pod shapes of Phaseolus vulgaris L. cv Tendercrop, were studied. The causes of build-up of off-type pods in a seed stock were examined as were possible means of reversing the buildup. Natural selection factors such as germination, vigor, earliness , and ease of threshing, favored the off-types. Careful, selective milling was found to be an aid to roguing in keeping stock seed as free as possible of the off-type pods.

The effects of vertical confinement on a neutrally-buoyant turbulent round jet discharging from a circular nozzle into quiescent shallow water were investigated. The focus was on identifying changes in the mean flow, turbulence characteristics, and large vortical structures of a horizontal water jet at different degrees of vertical confinement. The confinement resulted from the proximity of a lower solid wall and an upper free surface. The jet exit Reynolds number for all cases was 22,500. The depth of the water layer was the principal parameter. The axial and lateral confinements were negligible. Three different degrees of vertical confinement were investigated in addition to the free jet case. For the confined cases, the water layer depth was 15, 10 and 5 times the jet exit diameter. The centreline of the jet was located midway between the solid wall and the free surface. Particle image velocimetry (PIV) was used to investigate the flow behaviour. Measurements were taken on two orthogonal planes along the jet axis; one parallel and one perpendicular to the free surface. For each case, measurements were taken at three locations downstream of the jet exit where the effects of vertical confinement were expected to be significant. All image pairs were acquired at a frequency of 1 Hz using a 2048  2048 pixel camera. This rate was slow enough that the velocity fields were uncorrelated. At each location, two thousand image pairs were acquired in order to extract statistical information about the behaviour of the flow. <p>After completing the cross-correlation analysis of the PIV images and filtering outliers using a cellular neural network with a variable threshold, the statistical quantities such as mean velocities, turbulence intensities, Reynolds shear stress, centreline velocity decay, centreline turbulence intensities, and spread rate were obtained. The proper orthogonal decomposition (POD) technique was applied to the PIV data using the method of snapshots to expose vortical structures. The number of modes used for the POD reconstruction was selected to recover ~40% of the turbulent kinetic energy. An automated method was employed to identify the position, size, and strength of the vortices by searching for closed streamlines in the POD reconstructed velocity fields. This step was followed by a statistical study to understand the effect of vertical confinement on the frequency of vortex occurrence, size, strength, rotational sense, and preferred locations.<p>The results showed that the structure of the flow underwent significant changes because of the vertical confinement. The axial velocity profiles in the vertical plane become almost uniform over the entire depth with a mild peak below the centreline of the jet for the shallowest case, while the axial velocity profiles in the horizontal plane are Gaussian but narrower than the free jet profile. The mean vertical and horizontal velocity profiles show that fluid is drawn from the sides of the jet to its centreline and then diverted upward and downward from the jet axis. The decay rate of the mean centreline velocity becomes slower at downstream locations and the jet width becomes narrower in the horizontal mid-plane compared to the free jet case. The mixing efficiency of the fluid in the vertical plane is significantly inhibited by the confinement while there is a slight effect in the horizontal plane. Also, with increasing vertical confinement, the wall jet characteristics become more dominant. Investigation of the coherent structures revealed that at intermediate distances from the exit the population of vortical structures of either rotational sense is almost identical for all vortex sizes. At downstream locations in the vertical plane, this distribution is changed by the vertical confinement which causes a significant increase in the number of small clockwise vortices. In addition, it was observed that, as the confinement increases, the total number of vortical structures decreases and their sizes increase. This is evidence of the pairing process. Moreover, with increasing confinement the circulation decreases as the flow proceeds downstream on the vertical plane with a corresponding increase in the horizontal plane. This behaviour is consistent with the turbulence intensity results.

The effects of vertical confinement on a neutrally-buoyant turbulent round jet discharging from a circular nozzle into quiescent shallow water were investigated. The focus was on identifying changes in the mean flow, turbulence characteristics, and large vortical structures of a horizontal water jet at different degrees of vertical confinement. The confinement resulted from the proximity of a lower solid wall and an upper free surface. The jet exit Reynolds number for all cases was 22,500. The depth of the water layer was the principal parameter. The axial and lateral confinements were negligible. Three different degrees of vertical confinement were investigated in addition to the free jet case. For the confined cases, the water layer depth was 15, 10 and 5 times the jet exit diameter. The centreline of the jet was located midway between the solid wall and the free surface. Particle image velocimetry (PIV) was used to investigate the flow behaviour. Measurements were taken on two orthogonal planes along the jet axis; one parallel and one perpendicular to the free surface. For each case, measurements were taken at three locations downstream of the jet exit where the effects of vertical confinement were expected to be significant. All image pairs were acquired at a frequency of 1 Hz using a 2048  2048 pixel camera. This rate was slow enough that the velocity fields were uncorrelated. At each location, two thousand image pairs were acquired in order to extract statistical information about the behaviour of the flow. <p>After completing the cross-correlation analysis of the PIV images and filtering outliers using a cellular neural network with a variable threshold, the statistical quantities such as mean velocities, turbulence intensities, Reynolds shear stress, centreline velocity decay, centreline turbulence intensities, and spread rate were obtained. The proper orthogonal decomposition (POD) technique was applied to the PIV data using the method of snapshots to expose vortical structures. The number of modes used for the POD reconstruction was selected to recover ~40% of the turbulent kinetic energy. An automated method was employed to identify the position, size, and strength of the vortices by searching for closed streamlines in the POD reconstructed velocity fields. This step was followed by a statistical study to understand the effect of vertical confinement on the frequency of vortex occurrence, size, strength, rotational sense, and preferred locations.<p>The results showed that the structure of the flow underwent significant changes because of the vertical confinement. The axial velocity profiles in the vertical plane become almost uniform over the entire depth with a mild peak below the centreline of the jet for the shallowest case, while the axial velocity profiles in the horizontal plane are Gaussian but narrower than the free jet profile. The mean vertical and horizontal velocity profiles show that fluid is drawn from the sides of the jet to its centreline and then diverted upward and downward from the jet axis. The decay rate of the mean centreline velocity becomes slower at downstream locations and the jet width becomes narrower in the horizontal mid-plane compared to the free jet case. The mixing efficiency of the fluid in the vertical plane is significantly inhibited by the confinement while there is a slight effect in the horizontal plane. Also, with increasing vertical confinement, the wall jet characteristics become more dominant. Investigation of the coherent structures revealed that at intermediate distances from the exit the population of vortical structures of either rotational sense is almost identical for all vortex sizes. At downstream locations in the vertical plane, this distribution is changed by the vertical confinement which causes a significant increase in the number of small clockwise vortices. In addition, it was observed that, as the confinement increases, the total number of vortical structures decreases and their sizes increase. This is evidence of the pairing process. Moreover, with increasing confinement the circulation decreases as the flow proceeds downstream on the vertical plane with a corresponding increase in the horizontal plane. This behaviour is consistent with the turbulence intensity results.

ALe travail réalisé dans le cadre de cette thèse en co-tutelle est à cheval entre deux domaines d’étude de l’interférence de sillage d’obstacle non profilé (soit un cylindre ou deux cylindres en tandem) et celle des zones de recirculations dans un sluice artisanal (un appareil de tri d’or). Notre étude contribue à l’étude des écoulements à surface libre par combinaison de quelques méthodes expérimentales. Nous avons couplé quelques techniques entre autres la visualisation de la topologie du sillage proche par la caméra CCD embarquée, les mesures des champs de vitesse par PIV et des efforts hydrodynamiques. Ainsi, le cylindre animé d’un mouvement uniformément accéléré/décéléré est caractérisé par les forces de traînée et de portance, les enveloppes des maximas, la longueur de le zone de recirculation et le nombre de Strouhal local. Dont ce dernier a une valeur avoisinant de 0.4 près de la surface libre. Et entre deux pics de la portance, le déferlement de la vague d’accompagnement est observable. L’interférence entre deux structures est simulée à travers deux cylindres et que sur une configuration symétrique, le paramètre de proximité B a tendance à accroître la longueur de la zone de recirculation. Les méthodes et dispositifs expérimentales décrites ci-dessus sont appliqués dans le cas d’écoulement hydrodynamique turbulent au sein du sluice. Les essais sur sites aurifères à Madagascar ont permis la collecte des informations sur les paramètres optimums du tri. Ces paramètres sont pris comme base initiale des travaux de laboratoire entamés sur une maquette à l’échelle 1. L’acquisition par PIV suivi des traitements statistique à multi-variables POD Snapshot nous a permis de créer un modèle expérimental de l’écoulement composé de 4 zones distinctes. L’étude expérimentale a été complétée par une simulation numérique par ANSYS14.5 ; qui nous a permis de conclure que l’approchement des riffles entraîne une diminution de la zone favorable du dépôt des minerais lourds. / Two major areas are focused in the thesis. The first investigates the interference due to a wake-pattern of non-profiled obstacles (such as one or two cylinder in tandem). The second characterizes the zone of recirculation inside an artisanal sluice-boxe, which is a device for gold extraction. The work contributes to the study of the flow of a free-surface using experimental methods. Also, a few approaches is combined for the investigation. In this regard, the near-wake pattern of the flow is examined using an embedded CCD camera, correlated to a PIV measurement of the velocity fields and the hydrodynamic forces. We found that a cylinder of uniform motion, accelerated or decelerated, is characterized by: the drag and the lift forces, the envelopes of maxima, the length of the recirculation zone and the local Strouhal number. The Strouhal number approaches the value of 0.4 next to a free-surface and a breaking wave is observed in-between two peaks of the lift force. We modeled the interference between two structures using a succession of two cylinders. The proximity parameter B tends to an increase of the recirculation length for a symmetrical arrangement.Our methods and the experimental procedures are applied for the examination of a turbulent hydrodynamic flow inside a sluice. Tests were performed on gold sites in Madagascar. This permitted the collection of information concerning the optimum parameters for an extraction. The obtained values form the basis of our laboratory work and are applied to a scaled model for validation. An experimental flow model, made of four distinct zones, is derived from a monitored PIV data and a statistical analysis of a multi-variable POD snapshot. The results are validated through simulations using the package ANSYS 14.5. The investigation shows that a closer riffles reduces the region for heavy minerals deposition.

Ever since the revolutionary CubeSat form factor took hold in the Aerospace industry, there has been a desire to send them further and further into space. This thesis introduces an optimization approach to deployment that explores new possibilities of interplanetary CubeSats. In this approach there are three categories of objective functions that are defined by the type of trajectory of a “primary” spacecraft, which carries the CubeSat deployer. These categories are flyby, orbiter, and lander. For each category the objective function starts with four design variables. These are the ΔV of the deployer broken up into three component directions and the true anomaly at the time of deployment. The method then calculates the mission specific objective to be minimized and uses Matlab®’s built in gradient-based optimizer, fmincon. The results show that in the flyby category, the CubeSat has a significantly different turning angle than the primary. The CubeSat can even flyby on the opposite side of the planet. In the orbiter case it is shown that the method works by testing it with two objective functions, the difference in inclination and the difference in eccentricity between the primary and the CubeSat. It is shown that the inclination can be changed by 0.1314° and the eccentricity can be changed by 0.0033. These values, although low in magnitude, are an order of magnitude greater than non-optimal deployment scenarios. Still, another optimization method is introduced to find out how much extra ΔV the CubeSat would need to reach a desired change. This shows that with just an extra 75 m/s of ΔV, the CubeSat can change its orbit by 5°. This could come from either a propulsion system or a modified deployer. The final category, lander, used the flight path angle when entering the atmosphere as an objective. The method shows that flight path angle can be changed by 2.6°. Overall, these examples have proven that the method can find optimal solutions to CubeSat deployment scenarios at other planets.

This work is focused on computational modelling of a flow in a burner. The main objective is to provide a complex comparison of the results obtained through several approaches to modeling, on different computational grids and also using different turbulence models. Experimental measurement data are used for validation. Numerically obtained data are compared to each other and to experimental data. The method of Proper-Orthogonal Decomposition is also applied on the calculated data. The greatest benefit of this work is providing a wider view on the swirling flow modeling in burners and the results obtained here will help to better understand the behavior of stated models for tasks of this kind and their potential for modelling combustion in furnaces.