Instabilité, turbulence et couplages

Écoulements industriels

Écoulements biologiques

Écoulements pour la fusion magnétique


Instabilités, Turbulence et Couplages

L’équipe développe une expertise multidisciplinaire centrée autour de la modélisation numérique et de l’étude d’écoulements de fluides neutres ou ionisés (plasma) pour l’optimisation de systèmes industriels ou technologiques dans quatre grands domaines à fort impact sociétal : énergie, aménagement  et urbanisme, transport, et santé.
La physique de ces systèmes est celle des phénomènes hors-équilibres et couplés, avec des instabilités conduisant à la turbulence, et des interactions entre fluide et structure, mélange et transferts, turbulence et transport, … qui nécessitent le développement de méthodes et de codes de simulations originaux. Ces études souvent réalisées dans des régimes de paramètres pertinents pour l’application se font dans le cadre de collaborations fortes  avec nos partenaires socio-économiques (AIRBUS, SAFRAN, IRSN, CEA, ITER, AP-HM…) qui sont dans l’ADN de l’équipe.

L’équipe compte actuellement 12 chercheurs et enseignants chercheurs, et  structure son activité autour de 3 grandes familles d’écoulements.


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Annuaire personnel permanent

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Doctorants, Post-Doctorants et CDD

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Dernières publications de l'équipe

  • Mathis Pasquier, Stéphane Jay, Jérôme Jacob, Pierre Sagaut. A Lattice-Boltzmann-Based Modelling Chain for Traffic-Related Atmospheric Pollutant Dispersion at the Local Urban Scale. Building and Environment, 2023, 242, pp.110562. ⟨10.1016/j.buildenv.2023.110562⟩. ⟨hal-04190005⟩ Plus de détails...
  • L. Cappelli, N. Fedorczak, J. P. Gunn, S. Di Genova, J. Guterl, et al.. Study of the erosion and redeposition of W considering the kinetic energy distribution of incident ions through a semi-analytical model. Plasma Physics and Controlled Fusion, 2023, 65 (9), pp.095001. ⟨10.1088/1361-6587/ace282⟩. ⟨hal-04190861⟩ Plus de détails...
  • Franck Corset, Mitra Fouladirad, Christian Paroissin. Imperfect condition-based maintenance for a gamma degradation process in presence of unknown parameters. Proceedings of the Institution of Mechanical Engineers, Part O: Journal of Risk and Reliability, 2023, 237 (3), pp.546-561. ⟨10.1177/1748006X221134132⟩. ⟨hal-04064988⟩ Plus de détails...
  • G. Farag, P. Boivin, P. Sagaut. Linear interaction approximation for shock/disturbance interaction in a Noble–Abel stiffened gas. Shock Waves, 2023, ⟨10.1007/s00193-023-01131-8⟩. ⟨hal-04097657⟩ Plus de détails...
  • Jérémie Labasse, Uwe Ehrenstein, Guillaume Fasse, Frédéric Hauville. Thrust scaling for a large-amplitude heaving and pitching foil with application to cycloidal propulsion. Ocean Engineering, 2023, 275, pp.114169. ⟨10.1016/j.oceaneng.2023.114169⟩. ⟨hal-04032117⟩ Plus de détails...
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Dernières rencontres scientifiques

Soutenances de thèses et HDR

11 décembre 2023 - Modeling and analysis of the dynamics of viscoelastic fluids undergoing oscillatory forcing: application to mucus clearance / PhD Defense Amirhosein Nosrat Kharazmi
Doctorant : Amirhosein Nosrat Kharazmi  
Date : le lundi 11 décembre 2023 à 14h00 /  Centrale Méditerranée, Plot 6, Amphi n°3

Abstract :  Viscoelastic fluids are ubiquitous in the human body and more generally in nature, and their study offers numerous applications across various industrial sectors, including the health, biomedical, and pharmacy industries. They function as non-Newtonian fluids in several living system structures, including the human cardiovascular-pulmonary network, blood, and mucus, displaying both viscous and elastic characteristics. Due to their complex behavior, simulating numerically the dynamics of these fluids remains challenging because of the non-linear character of the equations and the associated numerical instabilities. In this work, a viscoelastic flow undergoing an unsteady forcing is simulated numerically by solving the momentum equations coupled to a constitutive equation for the fluid, namely the Oldroyd-B model. In this model, polymer molecules are considered as two beads connected by a spring and surrounded by a viscous fluid. To overcome the numerical instabilities arising from high elasticity effects, a hybrid lattice Boltzmann-finite difference method is proposed to solve viscous and elastic parts, respectively. The numerical approach is validated on several numerical benchmark test cases, including the Taylor green vortex, two-dimensional Poiseuille flow, and two-dimensional flow past a cylinder. The results present a good agreement with analytical solutions and literature reference data. A physical analysis of the dynamics of forced viscoelastic fluid flows is performed in the context of mucus clearance in the human respiratory system. The results show that the highest flow rate of mucus can be achieved in cases of resonance, i.e., when the frequency of the Womersley flow matches the natural frequency of the viscoelastic fluid. An increase in elasticity is found to lead to a higher mean flow rate in the case of viscoelastic shear-thinning fluids, while for Newtonian viscoelastic fluids, the mean flow is independent of elasticity. On the other hand, the flow rate decreases by adding yield stress to elasto-viscoplastic fluid. These results are meaningful in the context of biomedical devices improving mucociliary clearance of bronchial mucus. Keywords: lattice-Boltzmann method, viscoelastic fluid, Oldroyd-B equation, non-Newtonian flow, mucus, periodic forcing, bronchial clearance.


Directeur de these M. Julien FAVIER Aix Marseille Université

CoDirecteur de these M. Umberto D'ORTONA CNRS / Aix Marseille Université

Examinateur Mme Isabelle CHEYLAN Aix Marseille Université

Président M. Alistair REVELL University of Manchester

Rapporteur M. Hugues BODIGUEL Laboratoire Rhéologie et Procédés, Université Grenoble Alpes-Grenoble INP,

Rapporteur M. Gonçalo SILVA University of Évora

1 décembre 2023 - Heavy ions migration in tokamak boundary plasmas : development of a numerical model to interpret WEST experiments / PhD Defense Stefano Di Genova
Doctorant : Stefano Di Genova   
Date : le vendredi 1er décembre 2023 à 14h00 /  CEA-Cadarache, bâtiment 506, Cadarache, 13108, Saint-Paul-lez-Durance / Salle René Gravier 

Abstract :  Tungsten (W) is considered to be the most suitable material for the Plasma-Facing Components (PFCs) of future tokamak fusion reactors. Nonetheless, the deployment of this material in tokamak experiments has been shown to be detrimental to plasma discharges: W is eroded from the wall and contaminates the plasma, causing large power losses through radiation. Plasma operations in the W Environment Steady-state Tokamak (WEST) are heavily influenced by W contamination. In WEST discharges, the power loss due to W contamination is, on average, around 50% of the total power injected into the plasma. Moreover, the radiated power fraction is insensitive to plasma conditions. The causes behind this experimental trend are not fully understood. Furthermore, in experiments, it is not possible to detect which eroded PFCs impact the plasma W content the most. For these reasons, the experimental analysis of W contamination in WEST must be supported by modelling activities. The modeling of W migration in WEST helps estimate the W screening at the different PFCs and analyse the contamination trends in the tokamak. During this Ph.D. thesis, two well-established numerical tools (SOLEDGE and ERO2.0) are used to model the boundary plasma and the W migration in WEST plasma discharges. Based on simulations, a close analysis of the erosion of each WEST PFC and its impact on the plasma W content is performed. Results show that the WEST lower divertor is the most eroded PFC, but it is also the most screened one. On the other hand, less eroded components could impact the plasma W content more than the lower divertor. The tokamak upper divertor, the external surface of the baffle, and the antenna protections might be unscreened enough to influence the plasma W content even at low erosion rates. The research activity focuses on the antennas: 3D simulations of the boundary plasma are carried out using a complex wall geometry, the 3D wall is equipped with toroidally localized objects representing WEST antennas. The antenna protections are weakly screened, and the impact of their erosion on the plasma W content is predominant over the other PFCs one. The 3D model is used to analyze W migration over the WEST operational domain. The WEST database is sampled to obtain a scan of simulation input parameters that mimic the WEST plasma conditions over an experimental campaign. The simulation results are compared to WEST diagnostics data (reflectometry, Langmuir probes, and visible spectroscopy) to verify that the simulated plasma conditions are compatible with the WEST database. The W migration trend is analysed: the W density increases proportionally with the power entering the scrape-off layer and strongly drops when the radial distance between the separatrix and the antennas (Radial Outer Gap, ROG) increases. The radiated power is estimated in simulations with a simple 0D model. At a given ROG, the radiated power is proportional to the total injected power, with the radiated fraction which is not sensitive to plasma conditions. These trends are qualitatively and, at times, quasi-quantitatively comparable to what is observed in WEST experiments. In simulations, the radiated fraction is insensitivity to plasma conditions is related to the low screened W influx caused by the erosion of the antenna protections. This research activity shows how simplified numerical simulations of the boundary plasma and W migration can give a realistic picture of the W migration trends in tokamak experiments. The results also underline the importance of the main chamber PFCs located close to the confined plasma. Finally, this work points out how the net W influx coming from low screened PFCs might be weakly affected by plasma conditions and how it might become challenging to control during plasma discharges.


Directeur de these M. Eric SERRE M2P2, CNRS, Centrale Méditerranée, Aix Marseille Université

Président M. Khaled HASSOUNI LSPM, CNRS-UPR 3407, Université Paris 13

Rapporteur M. Karl KRIEGER Max-Planck-Institut für Plasmaphysik

Rapporteur M. David DONOVAN University of Tennessee Knoxville

Examinateur Mme Emmanuelle TSITRONE IRFM, CEA-Cadarache

Examinateur M. Paolo INNOCENTE Consorzio RFX

Examinateur M. Sebastijan BREZINSEK IEK-4 Forschungszentrum Jülich et Universität Düsseldorf

CoDirecteur de these M. Guido CIRAOLO IRFM, CEA-Cadarache 

27 septembre 2023 - Methodology for modeling installation effects on helicopter engines using a physical and machine learning approach / Soutenance de thèse Alexandre Di Marco
Doctorant : Alexandre DI MARCO
Date : le mercredi 27 septembre 2023 à 14h00 / Amphi n°3 - Centrale Méditerranée

Abstract : Helicopter performance is one of the most important elements for the competitiveness of the aircraft. This performance depends mainly on the available power, which comes essentially from its engine(s). Nevertheless, their operation requires an engine architecture, including an air intake and an exhaust system (nozzle), sensitive to environmental conditions. Thus, when the engine is integrated into the helicopter, the airflow entering the engine is subject to several aerothermal and/or aerodynamic disturbances, which can have a significant impact on the final power delivered by the engine as well as its operability. The difference between the power delivered by the engine in flight and the power delivered by the engine on the test bench is defined as installation effects. Usually, installation effects are determined during dedicated flight tests once the helicopter design is already fixed. Within the last few years, the arrival of the new generation of aircraft complexifies engine integration. In order to cope with the lack of upstream installation effect data during the development cycle impacting the final installed power and to reduce the risks associated with these new architectures, it is necessary to estimate the installation effects before the first flight tests. The objective of this thesis is to provide a methodological component for the modelization of installation effects, that can be used throughout the development of a helicopter. For this purpose, two approaches were investigated, a first approach called physical which is based on the modelization of the installation effects, and a second called Statistical based approach that aims to provide an additional level of information to the physical one. The first approach proposes a method for simulating installation effects before flight tests to reduce helicopter development costs and risks. It uses the reproduction of the engine's thermodynamic cycle coupled with computational fluid dynamics in the air inlet to predict the incoming flow into the engine. The results have been validated by comparison with dedicated flight tests, showing a good representation of installation effects with an accuracy of approximately 1%. This method can be used at any flight phase but does not capture the dispersion of effects. The second approach, called statistical, complements the weaknesses of the physical approach by considering the dispersion of installation effects. Additional CFD simulations with different helicopter attitudes allowed for a sensitivity analysis, demonstrating the importance of including the aircraft attitude in the simulation of installation effects. This combined approach, along with the simulation of installation effects, captures up to 90% of flight test points. Furthermore, a simulation method for installation effects based on machine learning allows for estimating the installation effects of an untested configuration using the flight test results obtained from another configuration. This approach combines machine learning and physics, thus reducing the number of flight tests required to define installation effects when modifying the air intake configuration. The use of these methods during the development process helps reduce risks and the number of flight tests needed to determine installation effects. Moreover, their applicability to all engine architectures and air intake configurations makes them a valuable set of tools for the development of new helicopters. 


Directeur de these M. Pierre SAGAUT AMU/M2P2

Rapporteur M. Nicolas BINDER ISAE-SUPAERO

Président Mme Mitra FOULADIRAD ECM/M2P2

Examinateur M. Nicolas GOURDAIN ISAE

Examinateur M. Jean-Christophe JOUHAUD CERFACS

Rapporteur M. Eric GARNIER ONERA