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The 4 December 2019 at 10h00

PhD defense – Gauthier WISSOCQ: “Investigation of lattice Boltzmann methods for turbomachinery secondary air system simulations”

Jean-François BOUSSUGE |  JCA CONFERENCE ROOM, CERFACS, Toulouse, France |  


Over the past decades, the optimization of turbomachinery efficiency has led to a constant increase in the air temperature of the primary vein. Nonetheless, large temperatures can considerably reduce the engine’s lifetime due to excessive thermal loads or uncontrolled clearances affected by thermal dilatation. An efficient and well-designed cooling system is therefore necessary. This is the role of the \textit{bore cooling} circuit, composed of successive rotating cavities in which a competition takes place between inertia, temperature gradients and forced convection induced by an axial throughflow. These phenomena give birth to complex, unsteady, non-axisymmetric flows of a priori unknown periodicity. Simulating such flows is a major challenge for numerical modeling since it requires solvers adapted to long and three-dimensional unsteady computations. The present thesis is devoted to the investigation of a particular method for the simulation of such flows: the lattice Boltzmann method (LBM). It combines the advantages of being inherently unsteady, relatively fast and perfectly adapted to complex three-dimensional geometries.
First, a study of instabilities occurring in rotating cavities subject to radial temperature gradients is proposed. To that end, linear stability analyses based on a local approach are applied to cases of annular geometries, representative of the axial planes of the rotating cavities. They are used to determine the flow structure in a linear regime as well as the critical Rayleigh and Reynolds numbers for instability occurrence. However, these analyses do not account for the non-linear effects of the limit cycle, which requires another method.
The thesis then focuses on the potential of the LBM for such simulations. A detailed investigation of the numerical instabilities that may occur under the conditions of application of the method is proposed. A particular methodology developed during this thesis, based on von Neumann’s approach, enables us to clearly identify the waves propagated by the scheme and underlines the numerical phenomena at the origin of instabilities. This study highlights the effect of many parameters on numerical stability such as the choice of the lattice and the collision model. A further analysis of regularized models highlights two fundamental properties of these schemes that have a strong influence on numerical stability for subsonic flows.
Applications of LBM to rotating cavity flows are finally performed. The commercial software PowerFLOW is used, being the only LBM solver mature enough to model perfect gases. The code is evaluated on academic cases of increasing complexity (two-dimensional cavity, closed cavity and rotating cavity with cooling throughflow). The results are compared with linear stability analyses, computations from the literature and experimental data. Finally, a multi-stage configuration is simulated, for which a conjugate heat transfer coupling (CHT) is carried out in order to take radiative transfers into account and make best use of the experimental data. The results highlight very good estimates of temperature distributions, hinting towards a good modelling of the complex phenomena contributing to heat transfer.


Pierre Sagaut                     Aix-Marseille Université (France)                                  Advisor

Jean-François Boussuge   CERFACS Toulouse (France)                                       Co advisor

Florian De Vuyst                UTC, Compiègne (France)                                             Referee

Tony Arts                           Von Karman Institute, Rhode St Genèse (Belgique)      Referee

Françoise Bataille              Université de Perpignan (France)                                  Member

Nicolas Gourdain              ISAE-Supaero, Toulouse (France)                                  Member

Farid Benyoucef                Safran AE Villaroche (France)                                       Invited member


Caution: please do not forget to get your ID card or passeport with you to present at the main entrance of Météo France.


Thierry Poinsot officially entered the French Academy of Sciences

CERFACS |  8 November 2021

Thierry Poinsot officially entered the French Academy of Sciences on October 12. See presentation here :Read more

The AVBP code from CERFACS at the heart of for PRACE projects from the 23rd call

CERFACS |  30 September 2021

Cerfacs is involved in three PRACE projects of the 23rd call for which hour allocation runs from 01/10/2021 to 30/09/2022. Researchers from ECL/LMFA UMR5509 (Ecole Centrale de Lyon) and IMFT (UMR 5502) laboratories have earned projects entirely based on the use of the LES solver developed by Cerfacs AVBP and involve the support of experts from the CFD and COOP teams underling the importance and effectiveness of collaborations between French labs and Cerfacs. Alexis Giauque from ECL/LMFA UMR5509 (Ecole Centrale de Lyon) has obtained not only one but two PRACE projects! The first project LESFAN (RA0101, 30 000 000 CPU hours on Irene/Rome TGCC) is based on the use of AVBP in the turbomachinery version to study the generation of noise by a fan of a real airplane engine. The second, PRACE-EDGES (RA0101, 40 000 000 CPU hours on Irene/Rome TGCC) focuses on LES modeling of dens gas in complex geometries. To do so, the LMFA Team has developed advanced thermodynamic closures in AVBP allowing the direct simulation of such flows. Laurent Selle from IMFT (UMR 5502) has received CPU hours for the GASTON project (RA0061, 30 000 000 CPU hours on Marenostrum BSC) which aims to study the structure of hydrogen flames in porous materials. For this, IMFT and Cerfacs will perform coupled simulations considering the reactive flow with AVBP as well as the conduction in the porous medium with AVTP which is known to play an central role in the flame stabilization process. Carlos Perez Arroyo from IMFT (UMR 5502) received 16 Mh CPU hours on Joliot-Curie Skylake partition to support his project WONDER.Read more