WorldCat Identities

Thobois, Ludovic

Overview
Works: 6 works in 7 publications in 2 languages and 9 library holdings
Roles: Author, Thesis advisor, Opponent
Publication Timeline
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Most widely held works by Ludovic Thobois
Intérêt et faisabilité de la simulation aux grandes échelles dans les moteurs automobiles by Ludovic Thobois( Book )

2 editions published in 2006 in French and held by 2 WorldCat member libraries worldwide

European environmental regulations obligate automotive manufacturers to develop less pollutant and less consuming engines. These engines are widely based on new combustion strategies, where mixing and aerodynamics need to be precisely controlled. Common aided development tools are no more adapted to predict accurately in space and time aerodynamics and mixing in new engines. RANS computations can not provide unsteady phenomena and engine test benches can not provide all the flow characteristics due to optical access. Large eddy simulation can be predicted through the motion of large turbulent eddies. The objectives of this work are to simulate engines geometries with the LES approach, to bring to front the advantages of the LES approach and to elaborate specific methodologies. On the one hand, LES is applied in steady-state flow benches in order to predict their discharge coefficient and their swirl number. Several flow benches have been tested. For all of them, LES results obtained are in agreement with experimental measurements. The final flow bench is the more realistic flow bench computed in this work. It is composed of two intake ports of a real Diesel engines. The LES approach gives insights into the understanding of flow generation and its dependance on valve lift. On the other hand, an ignition model (ADEL) is coupled to the turbulent combustion model TFLES. This model is then adapted to engine geometries, where thermodynamical conditions change. These two models are finally used to compute the combustion stroke of an indirect-injection gasoline engine. Four cycles of the engine are computed. The cycles obtained are in agreement with experimental cycles but they all differ. Cycle-to-cycle variations are analyzed in terms of mixing, aerodynamics, combustion and engine efficiency
Large Eddy Simulation of a Motored Single-Cylinder Piston Engine: Numerical Strategies and Validation by Benoit Enaux( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

Review of Lidar-Based Applications for Aviation Weather by Ludovic Thobois( )

1 edition published in 2018 in English and held by 2 WorldCat member libraries worldwide

Optimisation évolutionnaire multi-objectif parallèle : application à la combustion Diesel by Mouadh Yagoubi( )

1 edition published in 2012 in French and held by 1 WorldCat member library worldwide

Avec la sévérisation des réglementations environnementales sur les émissions polluantes (normes Euro) des moteurs d'automobiles, la nécessité de maitriser les phénomènes de combustion a motivé le développement de la simulation numérique comme outil d'aide à la conception. Tenant compte de la complexité des phénomènes à modéliser, et de l'antagonisme des objectifs à optimiser, l'optimisation évolutionnaire multi-objectif semble être la mieux adaptée pour résoudre ce type de problèmes. Cependant, l'inconvénient principal de cette approche reste le coût très élevé en termes de nombre d'évaluations qui peut devenir très contraignant dans le contexte des optimisations réelles caractérisées par des évaluations très coûteuseL'objectif principal de ce travail de thèse est de réduire le coût global des optimisations du monde réel, en explorant la parallélisation des algorithmes évolutionnaires multi-objectifs, et en utilisant les techniques de réduction du nombre d'évaluations (méta-modèles).Motivés par le phénomène d'hétérogénéité des coûts des évaluations, nous nous proposons d'étudier les schémas d'évolution stationnaires asynchrones dans une configuration parallèle de type « maître-esclave ». Ces schémas permettent une utilisation plus efficace des processeurs sur la grille de calcul, et par conséquent de réduire le coût global de l'optimisation.Ce problème a été attaqué dans un premier temps d'un point de vue algorithmique, à travers une adaptation artificielle des algorithmes évolutionnaires multi-objectifs au contexte des optimisations réelles caractérisées par un coût d'évaluation hétérogène. Dans un deuxième temps, les approches développées et validées dans la première partie sur des problèmes analytiques, ont été appliquées sur la problématique de la combustion Diesel qui représente le contexte industriel de cette thèse. Dans ce cadre, deux types de modélisations ont été utilisés: la modélisation phénoménologique 0D et la modélisation multidimensionnelle 3D. La modélisation 0D a permis par son temps de retour raisonnable (quelques heures par évaluation) de comparer l'approche stationnaire asynchrone avec celle de l'état de l'art en réalisant deux optimisations distinctes. Un gain de l'ordre de 42 % a été réalisé avec l'approche stationnaire asynchrone. Compte tenu du temps de retour très coûteux de la modélisation complète 3D (quelques jours par évaluation), l'approche asynchrone stationnaire déjà validée a été directement appliquée. L'analyse physique des résultats a permis de dégager un concept intéressant de bol de combustion permettant de réaliser un gain en termes d'émissions polluantes
Intérêt et faisabilité de la simulation aux grandes échelles dans les moteurs automobiles by Ludovic Thobois( )

1 edition published in 2007 in French and held by 1 WorldCat member library worldwide

European environmental regulations obligate automotive manufacturers to develop less pollutant and less consuming engines. These engines are widely based on new combustion strategies, where mixing and aerodynamics need to be precisely controlled. Common aided development tools are no more adapted to predict accurately in space and time aerodynamics and mixing in new engines. RANS computations can not provide unsteady phenomena and engine test benches can not provide all the flow characteristics due to optical access. Large eddy simulation can be predicted through the motion of large turbulent eddies. The objectives of this work are to simulate engines geometries with the LES approach, to bring to front the advantages of the LES approach and to elaborate specific methodologies. On the one hand, LES is applied in steady-state flow benches in order to predict their discharge coefficient and their swirl number. Several flow benches have been tested. For all of them, LES results obtained are in agreement with experimental measurements. The final flow bench is the more realistic flow bench computed in this work. It is composed of two intake ports of a real Diesel engines. The LES approach gives insights into the understanding of flow generation and its dependance on valve lift. On the other hand, an ignition model (ADEL) is coupled to the turbulent combustion model TFLES. This model is then adapted to engine geometries, where thermodynamical conditions change. These two models are finally used to compute the combustion stroke of an indirect-injection gasoline engine. Four cycles of the engine are computed. The cycles obtained are in agreement with experimental cycles but they all differ. Cycle-to-cycle variations are analyzed in terms of mixing, aerodynamics, combustion and engine efficiency
Simulation aux Grandes Echelles d'un moteur à allumage commandé - Evaluations des variabilités cycliques by Benoît Enaux( )

1 edition published in 2010 in French and held by 1 WorldCat member library worldwide

A major challenge for the development of internal combustion engines is to improve fuel economy and to reduce pollutant emissions while maintaining or enhancing engine performances. New strategies using downsizing with high levels of exhaust gas recirculation have this potential, but can impact on the combustion stability and trigger high cycle-to-cycle variations (CCV). The objective of this thesis is to set a methodology based on Large Eddy Simulation (LES) to study CCV of a Spark-Ignition (SI) engine. A gradual approach is used : the numerical tool is first evaluated on a motored axisymmetric piston-cylinder assembly, and then applied on a motored SI engine to validate the in-cylinder aerodynamic predictions. On this last configuration, the coupling with the turbulent combustion model DTFLES is added to simulate two operating points of the indirect injection engine mode. Each of these simulations takes into account one or several modeling key points (tetrahedra with moving mesh, the modelings of shock and ignition, and chemical kinetics) previously tested in academic configurations. This research work shows that LES approach, in the context of massively parallel computing, can be used to study the CCV of a realistic SI engine
 
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