Search

Your search keyword '"Aubert, Stéphane"' showing total 199 results
Start Over Author "Aubert, Stéphane"
199 results on '"Aubert, Stéphane"'

1. Quantum-Inspired Tensor Neural Networks for Option Pricing

Author

Patel, Raj G., Hsing, Chia-Wei, Sahin, Serkan, Palmer, Samuel, Jahromi, Saeed S., Sharma, Shivam, Dominguez, Tomas, Tziritas, Kris, Michel, Christophe, Porte, Vincent, Abid, Mustafa, Aubert, Stephane, Castellani, Pierre, Mugel, Samuel, and Orus, Roman

Subjects
Quantitative Finance - Pricing of Securities, Computer Science - Computational Engineering, Finance, and Science, Computer Science - Machine Learning, Quantum Physics
Abstract

Recent advances in deep learning have enabled us to address the curse of dimensionality (COD) by solving problems in higher dimensions. A subset of such approaches of addressing the COD has led us to solving high-dimensional PDEs. This has resulted in opening doors to solving a variety of real-world problems ranging from mathematical finance to stochastic control for industrial applications. Although feasible, these deep learning methods are still constrained by training time and memory. Tackling these shortcomings, Tensor Neural Networks (TNN) demonstrate that they can provide significant parameter savings while attaining the same accuracy as compared to the classical Dense Neural Network (DNN). In addition, we also show how TNN can be trained faster than DNN for the same accuracy. Besides TNN, we also introduce Tensor Network Initializer (TNN Init), a weight initialization scheme that leads to faster convergence with smaller variance for an equivalent parameter count as compared to a DNN. We benchmark TNN and TNN Init by applying them to solve the parabolic PDE associated with the Heston model, which is widely used in financial pricing theory., Comment: 11 pages, 8 figures, minor changes. arXiv admin note: substantial text overlap with arXiv:2208.02235

Published
2022

2. Quantum-Inspired Tensor Neural Networks for Partial Differential Equations

Author

Patel, Raj, Hsing, Chia-Wei, Sahin, Serkan, Jahromi, Saeed S., Palmer, Samuel, Sharma, Shivam, Michel, Christophe, Porte, Vincent, Abid, Mustafa, Aubert, Stephane, Castellani, Pierre, Lee, Chi-Guhn, Mugel, Samuel, and Orus, Roman

Subjects
Computer Science - Machine Learning, Condensed Matter - Strongly Correlated Electrons, Computer Science - Artificial Intelligence, Physics - Computational Physics, Quantum Physics
Abstract

Partial Differential Equations (PDEs) are used to model a variety of dynamical systems in science and engineering. Recent advances in deep learning have enabled us to solve them in a higher dimension by addressing the curse of dimensionality in new ways. However, deep learning methods are constrained by training time and memory. To tackle these shortcomings, we implement Tensor Neural Networks (TNN), a quantum-inspired neural network architecture that leverages Tensor Network ideas to improve upon deep learning approaches. We demonstrate that TNN provide significant parameter savings while attaining the same accuracy as compared to the classical Dense Neural Network (DNN). In addition, we also show how TNN can be trained faster than DNN for the same accuracy. We benchmark TNN by applying them to solve parabolic PDEs, specifically the Black-Scholes-Barenblatt equation, widely used in financial pricing theory, empirically showing the advantages of TNN over DNN. Further examples, such as the Hamilton-Jacobi-Bellman equation, are also discussed., Comment: 14 pages, 11 figures, minimal changes

Published
2022

3. Clinical utility of a deep-learning mortality prediction model for cardiac surgery decision making

Author

Achouh, Paul, Allou, Nicolas, Allyn, Jérôme, Aubert, Stéphane, Baufreton, Christophe, Bezon, Eric, Bonnet, Nicolas, Bouchot, Olivier, Braunberger, Eric, Camilleri, Lionel, Caus, Thierry, Chatel, Didier, Chavanis, Nicolas, Chocron, Sidney, Corbi, Pierre, Curtil, Alain, De Brux, Jean Louis, Delentdecker, Philippe, Deleuze, Philippe, Delmas, Benjamin, Demaria, Roland, Dervanian, Patrice, Doguet, Fabien, Fabre, Olivier, Folliguet, Thierry, Frapier, Jean-Marc, Frieh, Jean-Philippe, Jouan, Jérôme, Lapeze, Joël, Leprince, Pascal, Marcheix, Bertrand, Maureira, Juan Pablo, Mazzucotelli, Jean-Philippe, Nataf, Patrick, Obadia, Jean-François, Provenchere, Sophie, Roussel, Jean-Christian, Ruggieri, Vito Giovanni, Verhoye, Jean-Philippe, Vincentelli, André, Oliver, Matthieu, and Ferdynus, Cyril

Published
2023
Full Text
View/download PDF

4. Choke flutter instability sources tracking with linearized calculations

Author

Duquesne, Pierre, Rendu, Quentin, Aubert, Stéphane, and Ferrand, Pascal

Subjects
Physics - Fluid Dynamics, Physics - Classical Physics
Abstract

Purpose :The choke flutter is a fluid-structure interaction that can lead to the failure of fan or compressor blade in turbojet engines. In Ultra High Bypass Ratio (UHBR) fan, the choke flutter appears at part speed regimes and at low or negative incidence when a strong shock-wave chokes the blade to blade channel. Localization of main excitation sources and the understanding of the different work exchange mechanisms will help to avoid deficient and dangerous fan design. Design/methodology/approach :In this paper, an UHBR fan is analyzed using a time-linearized Reynolds-Averaged Navier-Stokes equation solver to investigate the choke flutter. The steady state and the imposed vibration (inter blade phase angle, reduced frequency and mode shape) are selected to be in choke flutter situation. Superposition principle induced by the linearization allow to decompose the blade in numerous small subsections to track the contribution of each local vibration to the global damping. All simulations have been performed on a 2D blade to blade extraction. Findings :Result analysis points to a restricted number of excitation sources at the trailing edge which induce a large part of the work exchange in a limited region of the airfoil. Main phenomena suspected are the shock-wave motion and the shock-wave/boundary layer interaction. Originality/value :An original excitation source tracking methodology allowed by the linearized calculation is addressed and applied to a UHBR fan test-case., Comment: International Journal of Numerical Methods for Heat and Fluid Flow, Emerald, 2019

Published
2019
Full Text
View/download PDF

6. Effect of Frozen Turbulence Assumption on the Local Blades Vibration on the Choke Flutter Instability in Transonic UHBR Fan

Author

Duquesne, Pierre, Aubert, Stéphane, Rendu, Quentin, Ferrand, Pascal, Hirschel, Ernst Heinrich, Founding Editor, Schröder, Wolfgang, Series Editor, Boersma, Bendiks Jan, Editorial Board Member, Fujii, Kozo, Editorial Board Member, Haase, Werner, Editorial Board Member, Leschziner, Michael A., Editorial Board Member, Periaux, Jacques, Editorial Board Member, Pirozzoli, Sergio, Editorial Board Member, Rizzi, Arthur, Editorial Board Member, Roux, Bernard, Editorial Board Member, Shokin, Yurii I., Editorial Board Member, Mäteling, Esther, Managing Editor, Braza, Marianna, editor, Hourigan, Kerry, editor, and Triantafyllou, Michael, editor

Published
2021
Full Text
View/download PDF

12. Clinical utility of a deep-learning mortality prediction model for cardiac surgery decision making

Author

Allou, Nicolas, primary, Allyn, Jérôme, additional, Provenchere, Sophie, additional, Delmas, Benjamin, additional, Braunberger, Eric, additional, Oliver, Matthieu, additional, De Brux, Jean Louis, additional, Ferdynus, Cyril, additional, Achouh, Paul, additional, Allou, Nicolas, additional, Aubert, Stéphane, additional, Baufreton, Christophe, additional, Bezon, Eric, additional, Bonnet, Nicolas, additional, Bouchot, Olivier, additional, Camilleri, Lionel, additional, Caus, Thierry, additional, Chatel, Didier, additional, Chavanis, Nicolas, additional, Chocron, Sidney, additional, Corbi, Pierre, additional, Curtil, Alain, additional, Delentdecker, Philippe, additional, Deleuze, Philippe, additional, Demaria, Roland, additional, Dervanian, Patrice, additional, Doguet, Fabien, additional, Fabre, Olivier, additional, Folliguet, Thierry, additional, Frapier, Jean-Marc, additional, Frieh, Jean-Philippe, additional, Jouan, Jérôme, additional, Lapeze, Joël, additional, Leprince, Pascal, additional, Marcheix, Bertrand, additional, Maureira, Juan Pablo, additional, Mazzucotelli, Jean-Philippe, additional, Nataf, Patrick, additional, Obadia, Jean-François, additional, Roussel, Jean-Christian, additional, Ruggieri, Vito Giovanni, additional, Verhoye, Jean-Philippe, additional, and Vincentelli, André, additional

Published
2023
Full Text
View/download PDF

14. L'intelligence artificielle (IA) comme aide à l'inventaire de l'avifaune nicheuse et migratrice des parcs solaires alpins.

Author

Aubert, Stéphane, Pradervand, Jean-Nicolas, and Jacot, Alain

Subjects
*ARTIFICIAL intelligence, *POWER resources, *ECOLOGICAL impact, *BIODIVERSITY, *MIGRATORY birds, *RENEWABLE energy standards
Abstract

The article explores the use of artificial intelligence (AI) to survey nesting and migratory bird species in Alpine solar parks, emphasizing the importance of understanding biodiversity in such areas before their establishment. Topics include the growing concern over energy supply in Switzerland, the ecological and societal implications of large-scale solar park projects in the Alps, and the urgent need for comprehensive ecological impact assessments to mitigate potential environmental harm.

Published
2024

16. GMRES Acceleration of Restricted Schwarz Iterations

Author

Pacull, Francois, Aubert, Stephane, Barth, Timothy J., Series editor, Griebel, Michael, Series editor, Keyes, David E., Series editor, Nieminen, Risto M., Series editor, Roose, Dirk, Series editor, Schlick, Tamar, Series editor, Erhel, Jocelyne, editor, Gander, Martin J., editor, Halpern, Laurence, editor, Pichot, Géraldine, editor, Sassi, Taoufik, editor, and Widlund, Olof, editor

Published
2014
Full Text
View/download PDF

17. Las subastas.

Author

Hoet, Marianne, de Saint Cyr, Arnaud Cornette, Aubert, Stéphane, and de Miguel, Mercedes

Published
2024

18. Veno-Arterial Extracorporeal Membrane Oxygenation for Circulatory Failure in COVID-19 Patients: Insights from the ECMOSARS Registry

Author

Anselmi, Amedeo, Mansour, Alexandre, Para, Marylou, Mongardon, Nicolas, Porto, Alizée, Guihaire, Julien, Morgant, Marie-Catherine, Pozzi, Matteo, Cholley, Bernard, Falcoz, Pierre-Emmanuel, Gaudard, Philippe, Lebreton, Guillaume, Labaste, François, Barbanti, Claudio, Fouquet, Olivier, Chocron, Sidney, Mottard, Nicolas, Esvan, Maxime, Fougerou-Leurent, Claire, Flecher, Erwan, Vincentelli, André, Nesseler, Nicolas, Pierrot, Marc, Flicoteaux, Guillaume, Mauriat, Philippe, Ouattara, Alexandre, Roze, Hadrien, Huet, Olivier, Fischer, Marc-Olivier, Alessandri, Claire, Bellaïche, Raphel, Constant, Ophélie, Roux, Quentin, Ly, André, Meffert, Arnaud, Merle, Jean-Claude, Picard, Lucile, Skripkina, Elena, Folliguet, Thierry, Fiore, Antonio, d'Ostrevy, Nicolas, Morgan, Marie-Catherine, Guinot, Pierre-Grégoire, Nguyen, Maxime, Gaide-Chevronnay, Lucie, Terzi, Nicolas, Colin, Gwenhaël, Fabre, Olivier, Astaneh, Arash, Issard, Justin, Fadel, Elie, Fabre, Dominique, Girault, Antoine, Ion, Iolande, Menager, Jean Baptiste, Mitilian, Delphine, Mercier, Olaf, Stephan, François, Thes, Jacques, Jouan, Jerôme, Duburcq, Thibault, Loobuyck, Valentin, Moussa, Mouhammed, Mugnier, Agnes, Rousse, Natacha, Manganiello, Sabrina, Desebbe, Olivier, Fellahi, Jean-Luc, Henaine, Roland, Richard, Jean-Christophe, Riad, Zakaria, Guervilly, Christophe, Hraiech, Sami, Papazian, Laurent, Castanier, Matthias, Chanavaz, Charles, Cadoz, Cyril, Gette, Sebastien, Louis, Guillaume, Portocarrero, Erick, Brini, Kais, Bischoff, Nicolas, Levy, Bruno, Kimmoun, Antoine, Mattei, Mathieu, Perez, Pierre, Bourdiol, Alexandre, Hourmant, Yannick, Mahé, Pierre-Joachim, Rozec, Bertrand, Vourc’h, Mickaël, Aubert, Stéphane, Bazalgette, Florian, Roger, Claire, Jaquet, Pierre, Lortat-Jacob, Brice, Mordant, Pierre, Nataf, Patrick, Patrier, Juliette, Provenchere, Sophie, Roué, Morgan, Sonneville, Romain, Tran-Dinh, Alexy, Wicky, Paul-Henri, Al Zreibi, Charles, Guyonvarch, Yannis, Hamada, Sophie, Bertier, Astrid, Harrois, Anatole, Matiello, Jordi, Kerforne, Thomas, Lacroix, Corentin, Brechot, Nicolas, Combes, Alain, Schmidt, Matthieu, Chommeloux, Juliette, Constantin, Jean Michel, D’alessandro, Cosimo, Demondion, Pierre, Demoule, Alexandre, Dres, Martin, Fadel, Guillaume, Fartoukh, Muriel, Hekimian, Guillaume, Juvin, Charles, Leprince, Pascal, Levy, David, Luyt, Charles Edouard, Pineton de Chambrun, Marc, Schoell, Thibaut, Fillâtre, Pierre, Massart, Nicolas, Nicolas, Roxane, Jonas, Maud, Vidal, Charles, Allou, Nicolas, Muccio, Salvatore, Di Perna, Dario, Ruggieri, Vito-Giovanni, Mourvillier, Bruno, Bounader, Karl, Launey, Yoann, Lebouvier, Thomas, Parasido, Alessandro, Reizine, Florian, Seguin, Philippe, Besnier, Emmanuel, Carpentier, Dorothée, Clavier, Thomas, Olland, Anne, Villard, Marion, Bounes, Fanny, Minville, Vincent, Guillon, Antoine, Fedun, Yannick, Ross, James, Laboratoire Traitement du Signal et de l'Image (LTSI), Université de Rennes (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM), CHU Pontchaillou [Rennes], Centre d'Investigation Clinique [Rennes] (CIC), Université de Rennes (UR)-Hôpital Pontchaillou-Institut National de la Santé et de la Recherche Médicale (INSERM), Laboratoire de Recherche Vasculaire Translationnelle (LVTS (UMR_S_1148 / U1148)), Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Paris Cité (UPCité)-Université Sorbonne Paris Nord, Institut Mondor de Recherche Biomédicale (IMRB), Institut National de la Santé et de la Recherche Médicale (INSERM)-IFR10-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12), IMRB - PROTECT/'Pharmacologie et Technologies pour les Maladies Cardiovasculaires' [Créteil] (U955 Inserm - UPEC), Institut National de la Santé et de la Recherche Médicale (INSERM)-IFR10-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Institut National de la Santé et de la Recherche Médicale (INSERM)-IFR10-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12), Pôle des Cardiopathies Congénitales du Nouveau-Né à L'adulte - Centre Constitutif Cardiopathies Congénitales Complexes M3C, Groupe Hospitalier Paris Saint-Joseph, Hôpital Marie-Lannelongue, Inserm U999, Université Paris-Saclay, Research on Healthcare Performance (RESHAPE - Inserm U1290 - UCBL1), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de la Santé et de la Recherche Médicale (INSERM), Innovations thérapeutiques en hémostase = Innovative Therapies in Haemostasis (IThEM - U1140), Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Paris Cité (UPCité), Centre recherche en CardioVasculaire et Nutrition = Center for CardioVascular and Nutrition research (C2VN), Aix Marseille Université (AMU)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Physiologie & médecine expérimentale du Cœur et des Muscles [U 1046] (PhyMedExp), Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM), Centre Hospitalier Régional Universitaire [Montpellier] (CHRU Montpellier), Unité de Recherche sur les Maladies Cardiovasculaires, du Métabolisme et de la Nutrition = Research Unit on Cardiovascular and Metabolic Diseases (ICAN), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU)-Institut de Cardiométabolisme et Nutrition = Institute of Cardiometabolism and Nutrition [CHU Pitié Salpêtrière] (IHU ICAN), CHU Pitié-Salpêtrière [AP-HP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-CHU Pitié-Salpêtrière [AP-HP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU), Franco-czech Laboratory for clinical research on obesity, Charles University [Prague] (CU)-Institut National de la Santé et de la Recherche Médicale (INSERM), MitoVasc - Physiopathologie Cardiovasculaire et Mitochondriale (MITOVASC), Université d'Angers (UA)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Nutrition, Métabolismes et Cancer (NuMeCan), and Université de Rennes (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)

Subjects
Heart Failure, [SDV.MHEP.CSC]Life Sciences [q-bio]/Human health and pathology/Cardiology and cardiovascular system, VA-ECMO, [SDV.IB]Life Sciences [q-bio]/Bioengineering, Outcomes, Covid-19
Abstract

International audience; Objectives: The clinical profile and outcomes of patients with Covid-19 who require veno-arterial or veno-venous-arterial extracorporeal membrane oxygenation (VA-ECMO - VAV-ECMO) are poorly understood. We aimed to describe the characteristics and outcomes of these patients and to identify predictors of both favorable and unfavorable outcomes.Methods: ECMOSARS is a multicenter, prospective, nationwide French registry enrolling patients who require VV/VA-ECMO in the context of Covid-19 infection (652 patients at 41 centers). We focused on 47 patients supported with VA- or VAV-ECMO for refractory cardiogenic shock.Results: Median age was 49. 14% of patients had a prior diagnosis of heart failure. The most common etiologies of cardiogenic shock were acute pulmonary embolism (30%), myocarditis (28%), and acute coronary syndrome (4%). E-CPR (Extracorporeal Cardiopulmonary Resuscitation) occurred in 38%. In-hospital survival was 28% in the whole cohort, and 43% when E-CPR patients were excluded. ECMO cannulation was associated with significant improvements in pH and FiO2 on day one, but non-survivors showed significantly more severe acidosis and higher FiO2 than survivors at this point (p = 0.030 and p = 0.006). Other factors associated with death were greater age (p = 0.02), higher BMI (p = 0.03), E-CPR (p = 0.001), non-myocarditis etiology (p = 0.02), higher serum lactates (p = 0.004), epinephrine (but not noradrenaline) use before initiation of ECMO (p = 0.003), hemorrhagic complications (p = 0.001), greater transfusion requirements (p = 0.001), and more severe SAVE and SAFE scores (p = 0.01 and p = 0.03).Conclusions: We report the largest focused analysis of VA- and VAV-ECMO recipients in Covid-19. Although relatively rare, the need for temporary mechanical circulatory support in these patients is associated with poor prognosis. However, VA-ECMO remains a viable solution to rescue carefully selected patients. We identified factors associated with poor prognosis and suggest that E-CPR is not a reasonable indication for VA-ECMO in this population.

Published
2023
Full Text
View/download PDF

19. Experimental Study on U-Beam Separator Device for Separating Solids from Gases.

Author

Aubry, Rémy, Debal, Matthieu, Aubert, Stéphane, and Rogaume, Yann

Subjects
REYNOLDS number, PARTICLE size distribution, SOLIDS, GASES
Abstract

The inertial separator, developed for fluidized beds, is a key component for optimizing large installations that separate solids from gases. Despite industrial interest and numerous patents, few studies have been conducted on this subject. In this paper, the geometric arrangement conditions were studied and evaluated. The efficiency of separating solids from gas depends on several factors, such as the granulometry, density, particle size distribution, velocity, humidity, and temperature of the system. For the mid-range of fluidized bed boilers (1–20 MWth), the experimental study selected all data to be in the same condition as the industrial technology. The global performance of the system can be increased by 15% by selecting a better combination of the U-beam. Three rows of U-beams are a good compromise between performance and cost for high Reynolds numbers, while only two rows seem to be enough for lower Reynolds numbers. [ABSTRACT FROM AUTHOR]

Published
2023
Full Text
View/download PDF

22. UHBR Open-Test-Case Fan ECL5/CATANA

Author

Pagès, Valdo, primary, Duquesne, Pierre, additional, Aubert, Stéphane, additional, Blanc, Laurent, additional, Ferrand, Pascal, additional, Ottavy, Xavier, additional, and Brandstetter, Christoph, additional

Published
2022
Full Text
View/download PDF

27. Improvements of the refinement pattern of Adaptive Particle Refinement

Author

Chanéac, Joffrey, Duquesne, Pierre, Aubert, Stéphane, Marongiu, Jean-Christophe, Laboratoire de Mecanique des Fluides et d'Acoustique (LMFA), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), and ANDRITZ Hydro

Subjects
[MATH]Mathematics [math]
Abstract

International audience; The Adaptive Particle Refinement (APR) method results in a coupling between two SPH domains composed by either larger particles (mothers) or smaller particles (daughters). APR is one of the most promising local refinement techniques for SPH. The 2D dam break and shock tube test cases are used for validation purpose, with satisfactory results in comparison with reference solutions. An oscillating 2D channel test case is also simulated. It is found that the APR method has a lack of robustness in Lagrangian simulations of flows going back and forth. The refinement process appears to be particularly sensitive to the pre-existing daughters within the refining mother neighbourhood. The present paper aims to improve the APR method robustness, performing the refinement of a mother regarding its neighbourhood. Therefore, an optimization problem is formulated to determine the accurate amount, positions and variables of the new daughters to create. For the oscillating channel test case, results are compared qualitatively to previous works. The proposed refinement improves the robustness.

Published
2021

28. UHBR OPEN-TEST-CASE FAN ECL5/CATANA, PART 2: MECHANICAL AND AEROELASTIC STABILITY ANALYSIS

Author

Pagès, Valdo, Duquesne, Pierre, Aubert, Stéphane, Blanc, Laurent, Ferrand, Pascal, Ottavy, Xavier, Brandstetter, Christoph, Laboratoire de Mecanique des Fluides et d'Acoustique (LMFA), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Tribologie et Dynamique des Systèmes (LTDS), Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Ecole Nationale d'Ingénieurs de Saint Etienne-Centre National de la Recherche Scientifique (CNRS), European Project: 864719,CATANA, European Project, and Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Ecole Nationale d'Ingénieurs de Saint Etienne (ENISE)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Aeroelastic, Composite, Aeroacoustic, Fan, [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]
Abstract

International audience; In Part-1, the ECL5 open-test-case has been introduced. Details on design methodology, geometry, and aerodynamics of the whole stage have been presented. Part-2 focuses herein on structure dynamics and aeroelastic stability. This paper aims to provide the mechanical and aeroelastic stability characteristics of the fan stage obtained with a state-of-art industrial design process. The fan blades are composed of a laminate made of unidirectional carbon fibres and epoxycomposite plies. Fibre orientations of each ply are parameters which enable to modify the mechanical behaviour with minimal impact on the aerodynamic performance. Details on the structural properties, the manufacturing process and the ply orientations are presented. First mechanical modes of the fan are described and discussed in the context of aeroelastic interactions. Their frequency distribution is validated in terms of synchronous vibration. Aeroelastic stability of the fan is evaluated at representative operating points with a systematic approach. Potential instabilities are observed far from the operating line. Therefore, they do not compromise experimental campaigns.

Published
2021

29. UHBR OPEN-TEST-CASE FAN ECL5/CATANA PART 1: GEOMETRY AND AERODYNAMIC PERFORMANCE

Author

Brandstetter, Christoph, Pagès, Valdo, Duquesne, Pierre, Ottavy, Xavier, Ferrand, Pascal, Aubert, Stéphane, Blanc, Laurent, Laboratoire de Mecanique des Fluides et d'Acoustique (LMFA), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Tribologie et Dynamique des Systèmes (LTDS), Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Ecole Nationale d'Ingénieurs de Saint Etienne-Centre National de la Recherche Scientifique (CNRS), European Project: 864719,CATANA, Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Ecole Nationale d'Ingénieurs de Saint Etienne (ENISE)-Centre National de la Recherche Scientifique (CNRS), and European Project

Subjects
Aeroelastic, Composite, Aeroacoustic, Flutter, Fan, [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]
Abstract

International audience; Application of composite rotors enables disruptive design possibilities but demands for a fundamental understanding of the dynamic behaviour to ensure robust design and safe operation. Sensitivity to multi-physical resonance between aerodynamic, structure-dynamic and acoustic phenomena is amplified in modern low speed fan designs for UHBR application. Very thin blades, which are required to maintain high efficiency at transonic flow conditions, are flexible and prone to vibrations. As a result, aeroelastic and aeroacoustic problems increasingly set the stability limit. Test cases of representative geometries without industrial restrictions are a key element of an open scientific culture but currently non-existent in the turbomachinery community. The most commonly used test cases in computational fluid dynamics (e.g. NASA Rotor37/67; TUD Rotor 1 etc.) were designed over two decades ago, and their aeroelastic characteristics are not representative of modern turbomachinery. Also, available experiments have not been conducted with a focus on coupling-phenomena and hence did not comprise multi-physical instrumentation. In order to provide a multi-physical validation benchmark representative of near-future UHBR fan concepts, the open-test-case fan stage ECL5 has been developed at Ecole Centrale de Lyon. Design intention was to develop a geometry with high efficiency and a wide stability range that can be realized using layered carbon fibre composites. The final design iteration of the fan stage is currently fabricated and will be experimentally tested within the European CleanSky-2 project CATANA (Composite Aeroelastics and Aeroacoustics, catana.ec-lyon.fr). In Part-1 of this publication, the test case is introduced with details on geometry, methodology and aerodynamic design of the whole stage, whereas Part-2 focuses on structure dynamics and aeromechanical stability. An analysis of the calculated aerodynamic performance with a focus on critical flow structures like tip-leakage flow, radial flow migration and flow separations is presented. Furthermore, details on the experimental campaign comprising multi-physical instrumentation anticipated for 2021 are given to highlight the research focus.

Published
2021

32. Efficacy of parasternal block to decrease intraoperative opioid use in coronary artery bypass surgery via sternotomy: a randomized controlled trial

Author

Bloc, Sébastien, primary, Perot, Brieuc P, additional, Gibert, Hadrien, additional, Law Koune, Jean-Dominique, additional, Burg, Yannick, additional, Leclerc, Didier, additional, Vuitton, Anne-Sophie, additional, De La Jonquière, Christophe, additional, Luka, Marine, additional, Waldmann, Thierry, additional, Vistarini, Nicolas, additional, Aubert, Stéphane, additional, Ménager, Mickaël M, additional, Merzoug, Messaouda, additional, Naudin, Cécile, additional, and Squara, Pierre, additional

Published
2021
Full Text
View/download PDF

40. 3D effects on flutter prediction in aeronautic compressor

Author

Duquesne, Pierre, Mahieux, Bruno, Aubert, Stéphane, Ferrand, Pascal, Laboratoire de Mecanique des Fluides et d'Acoustique (LMFA), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Safran Aircraft Engines, Association Française de Mécanique, and JARDIN, Nicolas

Subjects
Compressor, L-URANS, [SPI.MECA.MEFL] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph], Flutter, [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]
Abstract

The flutter corresponds to an aerodynamic loading which amplifies the natural vibration of the structure.This fluid-structure interaction can lead to the failure of compressor blades. In the design stage, thedetection of flutter is estimated in a 2D radial plan (a blade to blade cut, near the shroud). The studies on modern designs point to some disparity between these predictions and experimental test. In this paper, 3D and 2D simulations have been conducted on the rotor of a modern design of high pressure axial compressor to investigate the limitations of the 2D approach.To solve the steady flow, the Reynolds-Averaged Navier-Stokes (RANS) simulations with k-ω turbulence model has been performed with elsA solver. The blade motion corresponding to the first torsion mode attwo nodal diameters has been imposed on the blade. Then, the flow fluctuations have been determined by the time-linearized RANS solver Turb’lin.Depending on the operating condition, regressive pressure waves from the trailing edge can travel up to the shock wave. Approaching the shock wave, pressure wave amplitudes increase and induce important pressure fluctuations. In the 3D calculation pressure waves can escape in radial direction. The pressure wave radial deviation cannot be captured with a 2D calculation and has an impact on the work exchange., Le flottement correspond à un chargement aérodynamique qui amplifie les modes propres de la structure. Cette interaction entre le fluide et la structure peut mener à la destruction des aubages du compresseur. Lors des premières phases de conception d'un compresseur, le déclenchement du flottement est estimé dans un plan 2D (coupe aube à aube, proche du carter). Sur des géométries modernes, plusieurs études montrent une différence entre cette prédiction et les essais expérimentaux. Dans cet article, des simulations numériques 2D et 3D ont été effectuées sur la roue d'une géométrie moderne de compresseur axial pour évaluer les limites de l'approche 2D. Le logiciel elsA a été utilisé pour obtenir le champ stationnaire à partir d'une simulation RANS (Reynolds-Averaged Navier-Stokes) avec un modèle de turbulence k-ω. Le mouvement imposé à l'aube correspond au premier mode de torsion avec deux diamètres nodaux. Par la suite, les fluctuations de l'écoulement ont été déterminées en utilisant le solveur RANS linearisé en temps Turb'lin. Selon les conditions d'opération, les ondes de pression régressives provenant du bord de fuite peuvent remonter l'écoulement jusqu'à l'onde de choc. En se rapprochant de l'onde de choc, l'amplitude des ondes de pression augmente et induit d'importantes fluctuations de pression. Dans un calcul 3D, les ondes de pression peuvent s'échapper dans la direction radiale. Cette déviation radiale ne peut par contre pas être capturée avec un calcul 2D et cela modifie l'échange de travail.

Published
2019

44. Effect of nodal diameter on the local blades vibration on the choke flutter instability in transonic UHBR fan

Author

Duquesne, Pierre, Aubert, Stéphane, Rendu, Quentin, Ferrand, Pascal, Laboratoire de Mecanique des Fluides et d'Acoustique (LMFA), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), and JARDIN, Nicolas

Subjects
[SPI.MECA.VIBR]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Vibrations [physics.class-ph], [SPI.MECA.VIBR] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Vibrations [physics.class-ph]
Abstract

International audience; For some blade vibration situation (frequency, modeshape and nodal diameter) and some operating condition, the flow around a fan blade can amplify the natural vibration of the blade. This effect can lead to the failure of the blade. In this paper, the choke flutter instability is analysed based on the resolution of time-linearised Reynolds-Averaged Navier-Stokes on a 2D blade to blade extraction of an Ultra High Bypass Ratio (UHBR) fan named ECL5v1. The flow condition corresponds to choke flutter typical situation : a strong shockwave chokes the blade to blade channel. The blade vibration is represented by analytical motion of rotation of the profile around its leading edge. For a low reduced frequency (0.15), and certain Inter Blade Phase Angle (at 90°, equivalent to a nodal diameter at 4), choke flutter instability happens. In this case of flutter instability, a method of vibration decomposition has been performed. That has allowed the determination of the main local flutter sources and the main zones excited by each source. Two main work exchange sources are located side by side on the pressure side near the trailing edge. Both sources induce a work exchange at the traversing shockwave, particularly on the suction side where a flow separation happens. Next, the effect of the nodal diameter variation on these two main sources and their corresponding zone of work exchange are investigated in the range from -6 to 6. Flutter sources exist at a similar position and with the same work exchange sign for the different nodal diameter but their work exchange magnitude are modified. Different pressure wave propagation mechanisms are suspected to explain this evolution.

Published
2018

45. Multi-objective shape optimization of a plate heat exchanger: a multi-scale approach

Author

Mastrippolito, Franck, Aubert, Stéphane, Ducros, Frédéric, Ferrand, Martin, Fourmigué, Jean-François, Laboratoire de Mecanique des Fluides et d'Acoustique (LMFA), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Mécanique des Fluides, Energies et Environnement (EDF R&D MFEE), EDF R&D (EDF R&D), EDF (EDF)-EDF (EDF), and MASTRIPPOLITO, Franck

Subjects
[PHYS.MECA.THER] Physics [physics]/Mechanics [physics]/Thermics [physics.class-ph], [MATH.MATH-OC] Mathematics [math]/Optimization and Control [math.OC], adaptive sampling, [INFO.INFO-MO]Computer Science [cs]/Modeling and Simulation, Multi-objective optimization, Kriging, Heat exchanger, [PHYS.MECA.THER]Physics [physics]/Mechanics [physics]/Thermics [physics.class-ph], [PHYS.MECA.MEFL] Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [INFO.INFO-MO] Computer Science [cs]/Modeling and Simulation, [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [MATH.MATH-OC]Mathematics [math]/Optimization and Control [math.OC], CFD, [PHYS.PHYS.PHYS-DATA-AN] Physics [physics]/Physics [physics]/Data Analysis, Statistics and Probability [physics.data-an], [PHYS.PHYS.PHYS-DATA-AN]Physics [physics]/Physics [physics]/Data Analysis, Statistics and Probability [physics.data-an], Self-Organizing Maps
Abstract

International audience; This work considers the shape optimization of a crossflow plate heat exchanger air/water. The two objectives are to maximize the effectiveness while minimizing the total pressure drop. The shape variation concerns a trapezoidal rib mounted on the hot channels plates. A multiscale approach is presented, coupling CFD simulations and a NTU method. The optimization method is based on a genetic algorithm and kriging metamodels with adaptive sampling. Infill criteria are the maximum mean square error (MMSE) and multipoints expected improvement (q-EI). A clustering of the Pareto front individuals highlights a finite number of optimal shapes.

Published
2018

46. On the use of Schur complement to improve the efficiency of RBF-based mesh deformation applied to internal cooling

Author

Mastrippolito, Franck, Aubert, Stéphane, Ducros, Frédéric, Buisson, Martin, Laboratoire de Mecanique des Fluides et d'Acoustique (LMFA), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Service de Thermo-hydraulique et de Mécanique des Fluides (STMF), Département de Modélisation des Systèmes et Structures (DM2S), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, and Buisson, Martin

Subjects
[SPI.MECA.THER]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Thermics [physics.class-ph], [SPI.MECA.MEFL] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph], ComputingMilieux_MISCELLANEOUS, [SPI.MECA.THER] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Thermics [physics.class-ph], [SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph]
Abstract

International audience

Published
2018

47. Optimisation de forme multiobjectif d'unéchangeur a plaques : approche multiéchelle

Author

Mastrippolito, Franck, Aubert, Stéphane, Ducros, Frédéric, Ferrand, Martin, Fourmique, Jean-François, MASTRIPPOLITO, Franck, Laboratoire de Mecanique des Fluides et d'Acoustique (LMFA), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Mécanique des Fluides, Energies et Environnement (EDF R&D MFEE), EDF R&D (EDF R&D), and EDF (EDF)-EDF (EDF)

Subjects
[PHYS.MECA.THER] Physics [physics]/Mechanics [physics]/Thermics [physics.class-ph], Self-organising maps, [PHYS.MECA.THER]Physics [physics]/Mechanics [physics]/Thermics [physics.class-ph], Optimisation multi-objectif, [PHYS.MECA.MEFL] Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [MATH.MATH-OC] Mathematics [math]/Optimization and Control [math.OC], [PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph], [MATH.MATH-OC]Mathematics [math]/Optimization and Control [math.OC], CFD, [PHYS.PHYS.PHYS-DATA-AN] Physics [physics]/Physics [physics]/Data Analysis, Statistics and Probability [physics.data-an], [PHYS.PHYS.PHYS-DATA-AN]Physics [physics]/Physics [physics]/Data Analysis, Statistics and Probability [physics.data-an], Krigeage
Abstract

International audience; Ce travail porte sur l’optimisation de l’efficacité et de la perte de charge totale d’un échangeur à plaques par variation de la forme d’une ailette. Une approche multiéchelle est proposée, liant une modélisation numérique de l’ailette à une méthode NUT. La méthode d’optimisation repose sur un algorithme génétique (NSGA-II) et un métamodèle (krigeage). Le métamodèle est construit itérativement à partir des maxima de variance et d’amélioration attendue. Une agrégation des résultats obtenus le long du front de Pareto met en évidence un nombre fini de formes optimales.

Published
2018

48. Local contribution of blades vibration on the choke flutter instability in transonic UHBR fan

Author

Duquesne, Pierre, Rendu, Quentin, Ferrand, Pascal, Aubert, Stéphane, JARDIN, Nicolas, Laboratoire de Mecanique des Fluides et d'Acoustique (LMFA), École Centrale de Lyon (ECL), Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), and 3AF

Subjects
Physics::Fluid Dynamics, Choke flutter instability, [SPI.MECA.VIBR]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Vibrations [physics.class-ph], [SPI.MECA.VIBR] Engineering Sciences [physics]/Mechanics [physics.med-ph]/Vibrations [physics.class-ph]
Abstract

International audience; In this paper, an Ultra High Bypass Ratio fan is analyzed using a time-linearized Reynolds-Averaged Navier-Stokes equation solver to investigate the choke flutter. Simulations have been performed on a 2D blade to blade extraction. The steady flow exhibits a strong shock-wave which chokes the blade to blade channel. A flow separation zone can be noticed near the shock-wave on the suction side. The inter blade phase angle (IBPA) and the reduced frequency have been set to obtain a case with a choke flutter instability. The blade is decomposed in 424 subsections to track the contribution of local vibration to the global damping. Results analysis point to a restricted number of excitation sources at the trailing edge which induce a large part of the work exchange on a limited region of the airfoil. Main phenomena suspected are the shock-wave motion and the shock-wave / boundary layer interaction.

Published
2018

Catalog

Books, media, physical & digital resources
See catalog results