Etude Numérique de L'ébullition Avec Adaptation - Gif-sur-Yvette, France - Université Paris-Saclay GS Sciences de l'ingénierie et des systèmes

Université Paris-Saclay GS Sciences de l'ingénierie et des systèmes
Université Paris-Saclay GS Sciences de l'ingénierie et des systèmes
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Gif-sur-Yvette, France

il y a 2 semaines

Sophie Dupont

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Sophie Dupont

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Description

Etude numérique de l'ébullition avec adaptation de maillage anisotrope // Numerical investigation of boiling with anisotropic mesh adaptation:

  • Réf
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ABG-111427

ADUM-46758

  • Sujet de Thèse 24/02/2023
  • Université Paris-Saclay GS Sciences de l'ingénierie et des systèmes
  • Lieu de travail
  • GIF-SURYVETTE
  • France
  • Intitulé du sujet
  • Etude numérique de l'ébullition avec adaptation de maillage anisotrope // Numerical investigation of boiling with anisotropic mesh adaptation
  • Mots clés
  • Mécanique des fluides, Méthodes numériques, Adaptation de maillage anisotrope, Programmation, Calcul Haute performance
  • Fluid Mechanics, Numerical Methods, Anisotropic Mesh Adaptation, Programming, High Performance Computing
    Description du sujet:


Heat exchangers are a key part of many industrial and practical processes and could involve two-phase flows to increase heat recovery through evaporation/condensation.

Many new designs try to take advantage of this evaporation latent heat to propose safer or more compact exchangers.

Combined with the fact that released vapour could be highly compressible while the generating liquid remains incompressible, the challenge is to build models able to tackle all these aspects.


  • More precisely, we can focus on two configurations hard to accurately model. The first one is a global warmingfriendly version of heat pump based on water as a refrigerant (instead of harmful CFC/HCFC) where water is a working fluid operating at low pressure (hundredth of atmospheric pressure). Apart from technological issues related to mechanical design of the heat exchanger, the key challenge is to be able to predict the efficiency improvement due to the freesurfacebursting vapour bubble nucleated at such low pressure. Usual twophase
- incompressible approaches fail to tackle high density ratio and highly compressible gas.
  • For both configurations, numerical modelling twophase flows with compressible gas aside incompressible liquid and with evaporation/condensation is a key point to better understand physics and will be at the heart of this thesis.
  • Study of twofluid flows is challenging due to complex topology of the moving interface and wide range of scales involved. Representation of the interface in twofluid flows in Eulerian Finite Volume framework is still an open challenge but we will focus for this study on the Sharp Interface method (SIM [4]) for its accuracy of position, its easy numerical conception and its ability to be consistent with interface effects as surface tension or phase change.
  • Flows of interest for this study are characterized by incompressibility or vicinity of incompressibility (so called lowMach regime). One approach to address these specific compressibility effects while avoiding numerical diffusion is to consider compressible system and to take care of the numerical design. This path is successfully explored with the allregime Lagrangeprojection numerical scheme coupled with Level-Set method [5] developed in previous PhD thesis.
  • To handle large range of scale in interfacial flows, automatic mesh refinement is a numerical strategy allowing to tackle this multiscale problem and has already proven its efficiency in both single and twofluid flows. However usual techniques are based on cartesian grids, which imposes unnecessary mesh constraints when underlying flow feature is along a single direction.
For example, flow field variations are steep normal to the interface, requiring mesh refinement while variations are smoother along the interface, thus less cell are needed:
by design, isotropic mesh refinement fails to relax cell size simultaneously in different directions.

  • Anisotropic mesh adaptation has been developed to tackle this issue and is quite efficient to reduce computational need by two orders of magnitude compared to best practised grid refinement on steady problems. Improvements have been added to extend the methodology to transient flows, including incompressible twophase flows. We propose to adopt this methodology in the proposed thesis to accurately describe the interface at very fine resolution to correctly capture these heat transfer and phase change while keeping performance and flexibility.

Début de la thèse : 01/10/2023
Nature du financement:

Précisions sur le financement:


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Programme blanc GS-SIS
Présentation établissement et labo d'accueil:

  • Université Paris-Saclay GS Sciences de l'ingénierie et des systèmes
    Etablissement délivrant le doctorat:
  • Université Paris-Saclay GS Sciences de l'ingénierie et des systèmes

Ecole doctorale:

  • 579 Sciences Mécaniques et Energétiques, Matériaux et Géosciences
  • Formation avec un solide bagage en méthodes numériques pour la mécanique des fluides ;
  • Compétences en langages de programmation scientifique (Fortran, C, C++) requises ;
  • Les compétences en programmation parallèle (OpenMP/MPI) seront appréciées.
  • Training wi
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