7.1.1 AeroSol

• Keyword:
  Finite element modelling
• Functional Description:
  The AeroSol software is a high order finite element library written in C++. The code has been designed so as to allow for efficient computations, with continuous and discontinuous finite elements methods on hybrid and possibly curvilinear meshes. The work of the team CARDAMOM (previously Bacchus) is focused on continuous finite elements methods, while the team Cagire is focused on discontinuous Galerkin methods. However, everything is done for sharing the largest part of code we can. More precisely, classes concerning IO, finite elements, quadrature, geometry, time iteration, linear solver, models and interface with PaMPA are used by both of the teams. This modularity is achieved by mean of template abstraction for keeping good performances. The distribution of the unknowns is made with the software PaMPA , developed within the team TADAAM (and previously in Bacchus) and the team Castor.
• News of the Year:

  The main highlight of 2022 concerning the AeroSol library was the hiring of Luca Cirrottola as an INRIA permanent engineer.

  In 2022, the development of the library was focused on the following points

  * Development environment - Work on the packaging with Guix. - Work on continuous integration by using Plafrim as gitlab runner, with dependencies handled by Guix (and Modules for legacy). - Fix of an old memory leak on PaMPA and integration in the packaging. - Beginning of work for merging the branch master, the branch used for Uhaina/Lagoon project, and the branch including turbulence models and axi models. - the development of a new library DM2 has started. It aims at replacing PaMPA.

  * General numerical feature of the library - Postprocessing on wall and lines, including computation of Cp and Cf - New finite elements for quads and hexa, based on Gauss-Lobatto or Gauss-Lagrange elements were added.

  * Work on SBM methods - Shifted boundary method for Neumann and Dirichlet boundary conditions, - development of high order derivative in some of the finite element classes

  * Low Mach number flows: - Low Mach number filtering was extended on quads. Implementation of dicrete semi-norms div and grad, extension of some fixes to full Euler with arbitrary EOS.

  * RANS turbulent flow computations: - Inlet/Outlet boundary conditions for Euler/Navier-Stokes systems allowing to get a stationary solution - HLLC numerical flux, exact jacobian with frozen wave speeds and extension to the RANS equations coupled to transport equations (turbulence models) - test case: laminar and turbulent flat plate, development and documentation of axisymmetric test case, - Fix of Spalart-Almaras model, negative fix handle - Beginning of implementation of coupled elliptic problem with Neumann and Dirichlet boundary conditions on one variable.

  * Flux-reconstruction - Implementation of Flux-Reconstruction methods on Cartesian meshes

• URL:
  https://­team.­inria.­fr/­cardamom/­aerosol/
• Contact:
  Vincent Perrier
• Participants:
  Mario Ricchiuto, Vincent Perrier, Héloïse Beaugendre, Christopher Poette, Marco Lorini, Jonathan Jung, Anthony Bosco, Luca Cirrottola, Romaric Simo Tamou, Ibtissem Lannabi
• Partner:
  BRGM

7.1.2 DM2

• Name:
  Distributed Mesh and Data Manager
• Keywords:
  HPC, Data parallelism, High order finite elements, Unstructured meshes, Hybrid meshes
• Functional Description:

  DM2 is a C++ library for managing mesh and data on mesh in a MPI parallel environment. It is conceived to provide parallel mesh and data management in high order finite element solvers for continuum mechanics.

  The user should provide a mesh file which is read by the library. Then DM2 is able to:

  - Read the mesh, and read the data provided in the mesh file, possibly in parallel

  - Redistribute the mesh in order to distribute the data on a given set of processors. This redistribution is made through a graph partitioner such as PARMETIS or PT-SCOTCH.

  - Allocate the memory in parallel if a number of unknown by entity type is provided by the user.

  - Centralize the data.

  - Compute the halo required for a numerical method. The halo is adapted for each of the possible discretization.

  - Renumber mesh elements for making a difference between mesh elements that need or need not communication.

  - Aggregate a mesh based on a metric for developing a multigrid method.

• News of the Year:

  This year, the development of the DM2 library began. We focused on - the mesh reading: the parallel mesh reader of AeroSol was reused and improved. It can

  * read a GMSH file with lines, triangles, quads, prisms, tetrahedra or pyramids, each cell or face being straight or curved.

  * the mesh reading can be performed in parallel

  * the mesh distribution when reading in parallel can rely on a geometrical prepartitioner

  - from the mesh reading, a C++ structure graph is built. When read in parallel, it is parallel consistent. Some work was done on the graph structure (c++ containers, adjacency list) for ensuring interoperability with C structures.

  " from the c++ structure, a graph c-structure compatible with scotch or metis can be built. A parallel mesh redistribution of this graph can be performed based on these software

• Contact:
  Vincent Perrier
• Participants:
  Vincent Perrier, Luca Cirrottola

7.1.3 UHAINA

• Keywords:
  Simulation, Ocean waves, Unstructured meshes, Finite element modelling
• Scientific Description:

  Operational platform for near shore coastal application based on the following main elements:

  - Fully-nonlinear wave propagation.

  - Wave breaking handled by some mechanism allowing to mimic the energy dissipation in breakers.

  - A high order finite element discretization combined with mesh and polynomial order adaptation for optimal efficiency.

  - An efficient parallel object oriented implementation based on a hierarchical view of all the data management aspects cared for by middle-ware libraries developed at Inria within the finite element platform Aerosol.

  - A modular wrapping allowing for application tailored processing of all input/output data (including mesh generation, and high order visualization).

  - Spherical coordinates based on a local projection on a real 3D spherical map (as of 2021)

  - Compilation with GUIX available (as of 2022)

  - Homogenization and standardization of code outputs and hazard quatification (as of 2022)

  - Correction of the management of dry/wet fronts in the presence of structures represented by a single high point (as of 2022)

  - Use of FES for the calculation of the tide directly in UHAINA through an API. New compilation option for activation (as of 2022)

  - Boundary conditions accounting tides from FES and corrected with the effect of the inverse barometer, for the simulation of the tidal propagation and the surge on domains at the regional scale (as of 2022)

  - Hydraulic connections (e.g. sewers) in the simulation of urban flooding (as of 2022)

  - Mass source term, for the injection of the volume of water overtopping structures not accounted in the elevation model during flooding episodes by sea surges (as of 2022)

• Functional Description:
  Waves simulation
• Contact:
  Mario Ricchiuto
• Participants:
  Mario Ricchiuto, Philippe Bonneton, David Lannes, Fabien Marche
• Partners:
  EPOC, IMAG, IMB

8.1.1 Improvement of the EB-RSM RANS model

Participants: Rémi Manceau.

External collaborators: Gustave Sporschill (formerly CAGIRE, now Dassault), F. Billard (Dassault), M. Mallet (Dassault), A. Colombié (ONERA), F. Chedevergne (ONERA), E. Laroche (ONERA), S. Benhamadouche (EDF), J.-F. Wald (EDF).

In order to accurately represent the complexity of the phenomena that govern the evolution of turbulent flows, an important part of our research focuses on the development of Reynolds-stress RANS models that take into account the wall/turbulence interaction by an original approach, elliptic blending 93, 97. Although this approach, has been successfully applied to various configurations (for instance 55), in order to take into account more subtle effects, during the theses of A. Colombié and G. Sporschill, in collaboration with ONERA and Dassault Aviation, respectively, we identified the importance of introducing a specific pressure diffusion model to correctly reproduce the dynamics of turbulence in impingement regions and in boundary layers subject to adverse pressure gradients, paving the way towards a wider application of the EB-RSM in aeronautics 116, 65, 114, 115, 15.

8.1.2 Extension of RANS turbulence models to mixed and natural convection

Participants: Rémi Manceau, Puneeth Bikkanahally, Sofen K. Jena.

External collaborators: S.M. Saad Jameel (formerly Cagire, now Plastic Omnium), V. Herbert (PSA-Stellantis), F. Dehoux (formerly Cagire, now Framatome), S. Benhamadouche (EDF).

In the mixed and natural convection regimes, as presented in two invited lectures 94, 95, the interaction mechanisms between dynamic and thermal fluctuations are complex and very anisotropic due to buoyancy effects, so that the natural turbulence modelling level to take them into account is second-moment closure, i.e., Reynolds-stress models. When associating the EB-RSM and the EB-DFM, several modifications had to be introduced in natural convection for the scrambling term, the length scale of the elliptic blending, and especially by substituting a mixed time scale for the dynamic time scale in the buoyancy production term of the dissipation equation, which has a drastic positive impact on the predictions in the natural convection regime. This work, carried out in collaboration with EDF, leads to the first linear Reynolds-stress model able to accurately represent the wall/turbulence interaction in forced, mixed and natural convection regimes 69. However, some industrial partners, in particular PSA Group (now Stellantis), who encounter natural convection flows in the underhood compartment of vehicles, do not wish to use such sophisticated models, so we have developed an algebraic version of the Reynolds stress equation which thus constitutes an extension of the eddy-viscosity models (buoyancy-extended Boussinesq relation), within the framework of S. Jameel thesis 87, 86, 85, which can be easily implemented into any industrial and/or commercial CFD code. The application of such models to various configurations of differentially-heated cavities showed that, depending on the situation, such buoyancy extensions can have an influence ranging from very significant to negligible 21.

8.1.3 HTLES: an original hybrid RANS/LES model

Participants: Rémi Manceau, Puneeth Bikkanahally, Mahitosh Mehta, Martin David.

External collaborators: Vladimir Duffal (formerly Cagire, now EDF), B. de Laage de Meux (EDF), H. Afailal (formerly CAGIRE, now IFPEN), Ch. Angelberger (IFPEN), A. Velghe (IFPEN).

Regarding hybrid RANS/LES, we have developed the HTLES (hybrid temporal LES) approach. The wall/turbulence interaction being fundamental for the applications of interest to EDF, V. Duffal's thesis 72 focused on the precise control of the transition from RANS to LES when moving away from the wall, through the improvement of the theoretical link between the turbulent scales and the form of the model equations, as well as the introduction of two different shielding functions to avoid the classical grid-induced separation and log-layer mismatch 1273, i.e., the strong erroneous sensitivity of the results to the near-wall mesh. A significant result is that the study of wall pressure fluctuations and their spectra on periodic hills showed that the HTLES approach could reproduce these spectra as well as LES, down to a lower cut-off frequency than in LES due to the coarser mesh and the presence of the RANS zone 72, which suggests encouraging prospects for the prediction of mechanical and thermal fatigue. In the framework of the ANR project Monaco_2025, the thesis of P. Bikkanahally is devoted to the extension of the HTLES approach to natural convection. In differentially heated cavities, due to the coexistence of turbulent boundary layers and a laminar region in the centre, the shielding function introduced by V. Duffal causes a deterioration of the results. Good results are obtained by using instead a new shielding function based on the resolution of an elliptic relaxation equation 91, 58. Moreover, the thesis of H. Afailal, in collaboration with IFPEN, was dedicated to the development of the HTLES for the non-reactive internal aerodynamics of spark ignition engines. The aim was to adapt this approach to non-stationary, cyclic flows with moving walls, for which the main challenge was to provide a reliable evaluation of the mean turbulent energy, which is a crucial parameter for the control of the transition from RANS to LES, and is obtained by explicitly applying a differential temporal filter during the simulation to separate the time-dependent mean and turbulent components of the flow 50.

8.1.4 Towards embedded LES

Participants: Rémi Manceau, Pascal Bruel, Puneeth Bikkanahally, Mahitosh Mehta, Martin David.

External collaborators: Fabien Dupuy (GD-Tech), Olivier Jegouzo (GD-Tech), Fabien Renard (GD-Tech).

In the framework of hybrid RANS/LES, a particularly attractive approach is Embedded LES, which consists in reserving the LES to a small area included in a global RANS domain, which is a particular strategy for using the zonal hybrid RANS/LES. However, the zonal approach is characterized by a pre-division between RANS and LES zones and a discontinuous interface, which prohibits any evolution of the scale of description of turbulence during the calculation, which would allow an adaptability of the model according to physical criteria determined during the calculation. Our objective is therefore to develop embedded LES in the context of continuous approaches (CELES, Continuous Embedded LES), in which the interface between RANS and LES is now a diffuse interface. In these approaches, the domain is not split into sub-domains, but the model evolves in a continuous manner so that it tends towards a RANS model or towards a LES model. The diffuse interface (grey area) is the transition area in which the model transitions from a RANS model to a LES model. It is then necessary, as in the zonal approach, to enrich the RANS solution by adding synthetic turbulence to avoid the drastic decrease of the total turbulent stress at the beginning of the LES zone which would strongly degrade the results. In the framework of the hybrid RANS/LES approach developed by Cagire, HTLES, this aspect consists in developing a volume enrichment approach based on a fluctuating force 26. The development of such a CELES approach is the main purpose of the just started CELTIC project (post-doc of P. Bikkanahally), in collaboration with the SME GD-Tech. An adaptive determination of the RANS and LES regions based on physical criteria is the subject of the post-doc of M. David, in the framework of the Asturies project.

8.2.1 Improvement of scalability through task-based programming

Participants: Vincent Perrier, Jonathan Jung, Sangeeth Simon.

External collaborators: M. Haefele (LMAP), Storm project-team, Hiepacs project-team.

Task based programming has emerged over about a decade as an alternative to classical imperative parallel programming based on MPI or on coarse grain OpenMP, since it provides more flexibility for addressing heterogeneous architectures. Task based programming has began entering the OpenMP standard since the 4.0 version, but still remains in specific libraries such as OMPss 74, Parsec 59 or StarPU 51 for their most advanced features. In 75, we have developed a two dimensional mock-up code for the first order finite volume approximation of the Euler system on structured meshes based on StarPU, yielding interesting results; for example, for a mesh partitioned into $N$ parts, the code may scale with more than $N$ cores; another example is the possibility to temporarily allocate a resource to IO and to use it again for computation once the IO is finished. From 2019 to 2022, S. Simon did his postdoc under the co-supervision of J. Jung, M. Haefele and V. Perrier for extending the mock-up code to second order finite volume, and to the three dimensional discontinuous Galerkin method for the compressible Navier-Stokes system. Within this project, we are also developing roof-line models for analyzing the different algorithms and try to explain their behaviour with respect to the architecture addressed. Currently, the 1D Galerkin method is implemented and the extension to multi-D is in progress. The work done was published in the conferences 35, 36.

8.3.1 Low-Mach-number schemes

Participants: Jonathan Jung, Vincent Perrier, Ibtissem Lannabi.

Unfortunately, the only fix we found in our previous work 63 that is accurate for high order acoustics computation is not Galilean invariant. This led us to try to tackle the problem in a different way than the numerical flux modification. We raised more fundamental questions on the connection between the low Mach number spurious mode responsible for a low accuracy and the long time behaviour of the wave system. In 88, we proved that on some finite domain configurations, the long time limit of the wave system exists, and that a numerical flux is low Mach number accurate if and only if its low Mach number acoustic development has a consistent long time behaviour. The spurious mode on the velocity at low Mach number can therefore be identified as the non-divergence-free part of the long time limit of the asymptotic acoustic system. Once this spurious mode is sharply identified, it can be filtered. This result is published in 14. Still based on this filtering method, a spurious mode was identified in the velocity obtained by the low Mach number fix which consists in centering the pressure. This spurious mode may jeopardize the convergence of the velocity. These results were communicated in 37, 38. We also had the opportunity to disseminate our previous work on low Mach number flows at different conferences 23, included invited ones 24, 22.

8.3.2 Development of high order numerical schemes for axisymmetric turbulent flows

Participants: Anthony Bosco, Jonathan Jung, Vincent Perrier.

Part of the Asturies project aims at deriving high order numerical schemes for turbulent compressible flows in axisymmetric geometry. This year, the work was focused on the three following points:

1. The derivation of conservative formulation for general advection-diffusion conservation laws in axisymmetric coordinates. This led to a new high order discontinuous Galerkin method for axisymmetric coordinates, which is optimal order and in which the source term are unambiguously discretized and defined. This work was disseminated in 17, 18.
2. The derivation of new boundary conditions for Euler and Navier Stokes equations, which allows to reach a steady state. This was validated on a laminar flat plate.
3. The debugging of a Spalart-Almaras model which was implemented in AeroSol but had never been validated. This led to our first RANS computation with the AeroSol library. This was disseminated in 19.

8.3.3 Artificial compressibility method for Mach zero combustion

Participants: Pascal Bruel.

External collaborators: C. Cristaldo (Universidade Federal do Pampa, Brazil), M. Donini (INPE, Brazil), F. Fachini (INPE, Brazil).

As a first step towards the simulation of low Mach reacting flows, an efficient methodology to simulate variable density flows in the Mach zero limit, either inert or reacting was developed. The approach combined a finite volume framework on fully staggered grids with the artificial compressibility method and a dual-time stepping. The resulting code proved to be versatile enough to cope with excellent accuracy with flow configurations ranging from unsteady cylinder wakes to unsteady laminar diffusion flames 70.

8.3.4 Multi-scale multiphase flows

Participants: Vincent Perrier, Kevin Schmidmayer.

As far as multiphase models are concerned, based on the ideas of 71, we have revisited the derivation of Baer-and-Nunziato models 53. Usually, models are derived by averaging the Euler system; then the system of PDE on the mean values contains fluctuations which are modeled, often leading to relaxation terms and interfacial velocity and pressure which should also be modeled. This can be achieved by using physical arguments 111 or by ensuring mathematical properties 66. In 105, we have followed a slightly different path: we have supposed that the topology of the different phases follows an explicit model: the sign of a Gaussian process. Some parameters of the Gaussian process (mean, gradient of the mean) are linked with the averaged values of the flow (volume fraction), whereas others (auto-correlation function) are linked with the subscale structure of the flow. The obtained system is closed provided the parameters of the Gaussian process are known. Also, the system dissipates the phase entropies. Under some hypotheses that can be interpreted physically, asymptotic models can be derived in the interface flow limit or in the limit where the two fluids are strongly mixed. In these limits, different previously proposed models are recovered 111, 77, which does not necessarily ensure the same phase entropy dissipation properties. This work was disseminated in the conferences 27, 28. V. Perrier was also invited in 29 for talking about this topic.

8.3.5 Shock-induced cavitation within a droplet

Participants: Kevin Schmidmayer.

External collaborators: L. Biasiori-Poulanges (ETH Zürich, Switzerland).

In 11, we investigated the shock-induced cavitation within a droplet which is highly challenged by the multiphase nature of the mechanisms involved. Within the context of heterogeneous nucleation, we introduced a thermodynamically well-posed multiphase numerical model accounting for phase compression and expansion, which relies on a finite pressure-relaxation rate formulation. We simulated (i) the spherical collapse of a bubble in a free field, (ii) the interaction of a cylindrical water droplet with a planar shock wave, and (iii) the high-speed impact of a gelatin droplet onto a solid surface. The determination of the finite pressure-relaxation rate was done by comparing the numerical results with the Keller–Miksis model, and the corresponding experiments of Sembian et al. and Field et al., respectively. For the latter two, the pressure-relaxation rate was found to be $\mu =3.5$ and $\mu =0.5$, respectively. Upon the validation of the determined pressure-relaxation rate, we ran parametric simulations to elucidate the critical Mach number from which cavitation is likely to occur. Complementing simulations with a geometrical acoustic model, we provided a phenomenological description of the shock-induced cavitation within a droplet, as well as a discussion on the bubble-cloud growth effect on the droplet flow field. The usual prediction of the bubble cloud center, given in the literature, was eventually modified to account for the expansion wave magnitude.

8.3.6 Modelling of visco-elastic solids in multiphase flows

Participants: Kevin Schmidmayer.

External collaborators: N. Favrie (Aix-Marseille Université, France).

As a work in progress, an extension of the model of diffuse solid–fluid interfaces 104, 76 is proposed to deal with arbitrary complex materials such as porous materials in presence of plasticity and damage. These are taken into account through Maxwell-type models and are cast in the standard generalized materials. The specific energy of each solid is given in separable form: it is the sum of a hydrodynamic part of the energy depending only on the density and the entropy, an elastic part of the energy which is unaffected by the volume change, and a compaction part taking into account the compaction effects. It allows us to naturally pass to the fluid description in the limit of vanishing shear modulus. In spite of a large number of governing equations, the model has a simple mathematical structure. The model is well posed both mathematically and thermodynamically, i.e. it is hyperbolic and compatible with both laws of thermodynamics. The resulting model can be applied in situations involving an arbitrary number of fluids and solids. In particular, we are showing the ability of the model to describe complex plasticity (Gurson 81) and damage (Mazars 101) models.

8.4.1 Effusion cooling

Participants: Rémi Manceau, Pascal Bruel.

External collaborators: Ph. Reulet (ONERA), E. Laroche (ONERA), D. Donjat (ONERA), F. Mastrippolito (formerly CAGIRE, now SAFRAN HE).

As regards wall cooling by effusion (multiple jets in crossflow), our MAVERIC experimental facility does not allow us to carry out thermal measurements, so we approached ONERA Toulouse to collaborate on the effects of gyration (angle of the jets with respect to the incident flow) on the heat transfer between the fluid and the wall, within the framework of the European project SOPRANO. We then took up the challenge of carrying out RANS simulations with the EB-RSM model on a configuration of unprecedented complexity for us, consisting of 10 rows of 9 holes, in 90-degree gyration, representative of effusion cooling problems in aeronautical combustion chambers. Comparisons between calculations and experiments have shown the relevance of using the EB-RSM model and the importance of taking into account conjugate heat transfer 107, 25.

8.4.2 Security of reservoirs and pipelines

Participants: Pascal Bruel.

External collaborators: S. Elaskar (University of Cordoba, Argentina), J. Saldia (University of Cordoba, Argentina), L. Gutiérrez Marcantoni (University of Cordoba, Argentina), A. Beketaeva (Institute of Mathematics and Mathematical Modelling, Almaty, Kazakhstan), A. Naimanova (Institute of Mathematics and Mathematical Modelling, Almaty, Kazakhstan).

In the framework of the cooperation with our international partners in Kazakhstan and Argentina, simulations of turbulent flows in different configurations were performed. The flow configurations ranged from the injection of a sonic jet in a supersonic crossflow 54, the interaction of an atmospheric boundary layer with aerial reservoir(s) 110 or of a channel flow with cylinders in tandem 79 to the simulation of a blast wave of Sedov-like type 82. The objectives of these simulations were twofold: 1) Assessing the predictive capabilities of conventional RANS approaches by comparisons with experimental data in order to establish the margin of progression that could be subsequently brought about by the recourse to the more elaborated turbulence models developed by our team and 2) Providing a knowledge of the sensitivity of the different flow topologies and characteristics to the variation of the relevant parameters describing the different configurations at hand. In parallel, our test facility MAVERIC was upgraded in order to accompany the forthcoming validation activities in the framework of the ASTURIES project and the partnership with our Argentinian colleagues.

8.4.3 Thermocline energy storage

Participants: Rémi Manceau, Alexis Ferré.

External collaborators: S. Serra (LaTEP, UPPA), J. Pouvreau (CEA), A. Bruch (CEA).

A collaboration started at the end of 2020 with the CEA LITEN in Grenoble and the LaTEP of UPPA on thermocline energy storage. An experimental facility is being developed at the CEA and RANS simulations are underway to understand the dynamics of this type of flows, to determine the influence of the turbulence generated by the filling of the tank on the quality of the thermocline, in order to optimize the system and provide data to support the development of 1D models used in the optimization of heat networks. A particular attention has been paid to the approximation used for variations of density with temperature. Due to the wide range of temperatures, it was shown that the standard Boussinesq approximation is not valid but a quadratic Boussinesq approximation was proposed, which gives results very close to the more complex low-Mach number approximation, with a computational cost reduced by a factor of two and an improved numerical stability 20.

10.1.1 Participation in other International Programs

ECOS-Sud A17A07 project with UNC (Córdoba, Argentine). 2022 was the last year of this project devoted to the experimental and numerical study of the wind around aerial fuel tanks. 1316.

10.2.1 Visits of international scientists

10.2.2 Visits to international teams

10.3.1 ANR MONACO_2025

Participants: Rémi Manceau.

The ambition of the MONACO_2025 project, coordinated by Rémi Manceau, is to join the efforts made in two different industrial sectors in order to tackle the industrial simulation of transient, turbulent flows affected by buoyancy effects. It brings together two academic partners, the project-team Cagire hosted by the university of Pau, and the institute Pprime of the CNRS/ENSMA/university of Poitiers (PPRIME), and R&D departments of two industrial partners, the PSA group and the EDF group, who are major players of the automobile and energy production sectors, respectively.

• The main scientific objective of the project is to make a breakthrough in the unresolved issue of the modelling of turbulence/buoyancy interactions in transient situations, within the continuous hybrid RANS/LES paradigm, which consists in preserving a computational cost compatible with industrial needs by relying on statistical approaches where a fine-grained description of the turbulent dynamics is not necessary. The transient cavity flow experiments acquired during MONACO_2025 will provide the partners and the scientific community with an unrivalled source of knowledge of the physical mechanisms that must be accounted for in turbulence models.
• The main industrial objective is to make available computational methodologies to address dimensioning, reliability and security issues in buoyancy-affected transient flows. It is to be emphasized that such problems are not tackled using CFD at present in the industry. At the end of MONACO_2025, a panel of methodologies, ranging from simple URANS to sophisticated hybrid models based on improved RANS models, was evaluated in transient situations, against the dedicated cavity flow experiments and a real car underhood configuration. This final benchmark exercise will form a decision-making tool for the industrial partners, and will thus pave the way towards high-performance design of low-emission vehicles and highly secure power plants. In particular, the project is in line with the Full Digital 2025 ambition, e.g., the declared ambition of the PSA group to migrate, within the next decade, to a design cycle of new vehicles nearly entirely based on CAE (computer aided engineering), without recourse to expensive full-scale experiments.

10.3.2 ANR LAGOON

Participants: Vincent Perrier.

The ANR project Lagoon was funded by ANR in 2021 within the section CE46 - Modèles numériques, simulation, applications.

Coastal areas host around 10% of the world's population and a huge amount of economic activities. Climate change is expected to increase coastal flooding hazard in years to come. In this project, we propose to develop a numerical tool for the stormsurges predictions.

For four years, a joint effort between the partners of this project among others has been done for the development of a numerical tool able to tackle planetary computations with high resolution at the coast: the Uhaina code, based on top of the AeroSol library. The scope of this project is to increase the computational performance of our modelling platform, in order to upgrade it as an efficient and accurate tool for storm-surge predictions in different future climate scenarios. To achieve this goal and producing results which go beyond the state-of-the-art, our efforts will be focused on the following numerical and informatics developments, devoted to decrease the run time of the model in operational conditions:

• Development of low-Froude accurate Implicit-Explicit (ImEx) time integration strategy.
• Development of scalable aggregation-based multigrid methods for addressing the efficiency of the inversion of the (non)linear systems induced by implicit time stepping. For the data generation, two stages IO, in-situ and in-transit data post-processing are strategies that will be evaluated with existing technologies and will be implemented to improve the performance of the production code.
• The numerical tool will be validated on 1979-2014 sea level reanalysis, and be used for the generation of a database of sea level projections on future climate CMIP6 projections.

The code developed within this project will be freely distributed, with a strong effort put on reproducibility of results. Data generated for both the sea level reanalysis and the database of sea level projection for future climate projections will be distributed towards the community.

10.3.3 ASTURIES

Participants: Rémi Manceau, Vincent Perrier, Jonathan Jung, Pascal Bruel, Anthony Bosco, Mahitosh Mehta, Romaric Simo Tamou, Martin David.

Call: ISite E2S UPPA "Exploring new topics and facing new scientific challenges for Energy and Environment Solutions"

Dates: 2020-2024

Partners: CEA CESTA ; IFPEN

In the context of internal turbulent flows, relevant to aeronautic and the automotive propulsion and energy production sectors, ASTURIES aims at developing an innovative CFD methodology. The next generation of industrial CFD tools will be based on the only approach compatible with admissible CPU costs in a foreseeable future, hybrid RANS/LES. However, state-of-the-art hybrid RANS/LES methods suffer from a severe limitation: their results are strongly user-dependant, since the local level of description of the turbulent flow is determined by the mesh designed by the user.

In order to lift this technological barrier, an agile methodology will be developed: the scale of description of turbulence will be locally and automatically adapted during the computation based on local physical criteria independent of the grid step, and the mesh will be automatically refined in accordance. Such an innovative approach requires the use of advanced near-wall turbulence closures, as well as high-order numerical methods for complex geometries, since low-dissipative discretization is necessary in LES regions. Morevover, the identification of relevant physical RANS-to-LES switchover criteria and the refined validation of the method will strongly benefit from dedicated experiments.

The objectives of the project thus consist in:

• Proposing a robust and efficient implementation of elliptic relaxation/blending turbulence models in the context of high-order Discontinuous Galerkine methods.
• Develop local physical criteria in order to get rid of the (explicit or implicit) dependence on the grid step of the transition from RANS to LES.
• Develop an automatic remeshing strategy which ensures consistency with the self-adaptation of the model.
• Validate the global methodology based on the 3 preceding points for configurations representative of industrial internal turbulent flows.

The development of such a methodology, based on hybrid RANS/LES modelling, with low-dissipative and robust numerical methods, independant of the initial design of a grid by the user, compatible with unstructured meshes for complex industrial geometries, in the context of HPC, is thus the ambitious, but reachable, objective of the project.

10.4.1 HPC scalable ecosystem

Participants: Jonathan Jung, Vincent Perrier, Sangeeth Simon.

HPC scalable ecosystem was a 3-year program funded by Région Nouvelle-Aquitaine (call 2018), Airbus, CEA-CESTA, University of Bordeaux, INRA, ISAE-ENSMA and Inria. Sangeeth Simon was hired as a post-doc with the objective of extending the prototype code developed in 75 to high order (discontinuous Galerkin) and non-reactive diffusive flows in 3D. The same basis will be developed in collaboration with Pprime for WENO based methods for reactive flows.

10.4.2 CELTIC

Participants: Rémi Manceau, Pascal Bruel, Puneeth Bikkanahally.

CELTIC (Continuous Embedded LES for Turbulent flows in Industrial Configurations) is a projet accepted in the call ESR 2022 of the New-Aquitaine Region, in partnership with the local SME GDTech.

The project aims at proposing a new model of the forcing term allowing enrichment at the diffuse interfaces between RANS and LES in continuous hybrid RANS/LES models for the simulation of turbulent flows. This will make possible the development of an innovative simulation methodology, continuous embedded LES (CELES), which consists in restricting the fine-grained model (LES) to regions where it is necessary, surrounded by the rest of the domain using a statistical approach (RANS). The combination of the fact that CELES will be based on hybrid RANS/Continuous LES approaches, easy to use in industrial applications, and on a seeding by volume forcing applicable in all situations will make it a particularly attractive method for the industry, which will bring to our industrial partner GDTech and its regional customers (for example SAFRAN HE) a real value compared to the numerical simulation methods available today.

11.1.1 Scientific events: organisation

11.1.2 Scientific events: selection

11.1.3 Journal

11.1.4 Invited talks

29 V. Perrier. “Stochastic derivation of models and numerical methods for multiphase compressible flows”. In: 34e Séminaire sur la mécanique des fluides numérique. Paris, France, 24th Jan. 2022.

25 F. Mastrippolito, R. Manceau and P. Bruel. “Modélisation des effets de giration pour les jets en écoulement transverse”. In: Journée thématique SFT : Aérothermique des systèmes propulsifs pour l'aéronautique. Paris, France, 20th Oct. 2022.

22 J. Jung, V. Perrier and I. Lannabi. “On low Mach number fixes for Roe-type schemes”. In: Rencontres de la thermohydraulique numérique du CEA/STMF. Saint-Rémy-lès-Chevreuse, France, 28th June 2022.

24 Jonathan Jung, Vincent Perrier "Relations between the low Mach number problem and the long time limit of the wave system". In Rencontres de la thermohydraulique numérique du CEA/STMFSaint-Rémy-lès-Chevreuse, France, 27th June, 2022

33 K. Schmidmayer. “Modeling and simulation of bubble dynamics in the diffuse-interface framework”. In: Workshop on Cavitation, bubble dynamics and mass transfer. Strasbourg, France, 31st May 2022.

34 K. Schmidmayer. “Modeling and simulation of bubble dynamics in the diffuse-interface framework”. In: ETH Zürich seminar. Zürich, Switzerland, 22th August 2022.

31 K. Schmidmayer. “Droplet shock-induced cavitation using a multiphase modelling approach”. In: Sorbonne University Seminar, Pierre and Marie Curie Campus, Institut Jean le Rond $\partial$’Alembert. Paris, France, 8th December 2022.

11.1.5 Leadership within the scientific community

• R. Manceau has been a member of the Standing committee of the Special Interest Group Turbulence modelling (SIG-15) of ERCOFTAC since 2005, together with 9 other committee members (S. Jakirlić [chairman], F. Menter, S. Wallin, D. von Terzi , B. Launder, K. Hanjalić, W. Rodi, M. Leschziner, D. Laurence). The main activities of the group is to organize international workshops and thematic sessions in international congresses.

• Rémi Manceau coordinates the ANR Project MONACO_2025, a 4-year project started in 2018. The partners are: the institute PPrime, PSA Group and EDF.

• Rémi Manceau coordinates the 4-year E2S-UPPA project ASTURIES, which involves CEA and IFPEN.

• Vincent Perrier coordinates the ANR Project LAGOON, a 4-year project started in 2022. The partners are: the CARDAMOM project-team of Inria Bordeaux and the BRGM.

11.1.6 Research administration

• Co-responsible for the organisation of the LMAP seminar of Mathematics and their Applications [Jonathan Jung].
• Member of the LMAP council [Rémi Manceau].

• Member of the CDT, in charge of the evaluation of software projects at the Inria Bordeaux center [Vincent Perrier].
• Elected member of the Inria evaluation committee and member of the board [Vincent Perrier]. 9
• Member of the CT3-Num committee of Pau University, in charge of managing the computing resources and projects at Pau University [Vincent Perrier].
• Member of the comité des utilisateurs des moyens de calcul at INRIA [Vincent Perrier]

11.2.1 Teaching

• L1 [J. Jung]: Research and innovation, 1.5h/year, Université de Pau et des Pays de l'Adour, Pau, France.
• L2 [J. Jung]: Numerical analysis for vectorial problems, 42.75h/year, Mathematics, Université de Pau et des Pays de l'Adour, Pau, France.
• M1 [J. Jung]: Tools for scientific computing, 48h75/year, MMS, Université de Pau et des Pays de l'Adour, Pau, France.
• M2 [J. Jung, V. Perrier]: Finite volume scheme for hyperbolic systems, 24h/year, MMS, Université de Pau et des Pays de l'Adour, Pau, France.
• M1 [J. Jung]: Supervised personal work, 5 h/year, MMS, Université de Pau et des Pays de l'Adour, Pau, France.
• M2: [V. Perrier], Finite volume scheme for hyperbolic systems, Master MMS, Pau. 24h/year.
• M2 [R. Manceau]: Turbulence modelling (in English), 27h30/year, International Master program Turbulence, ISAE-ENSMA/École centrale de Lille, France.
• E3 [R. Manceau]: Industrial codes for CFD (in English), 12h30/year, ISAE-ENSMA, Poitiers, France 47.
• E3 [R. Manceau]: Advanced physics–Turbulence modelling for CFD, 16h/year, ENSGTI, France 98.
• M1 [K. Schmidmayer]: Basics of heat transfer (in English), 30h/year, International Master's SIMOS, ENSGTI, Pau, France.
• M1 [K. Schmidmayer]: Heat exchangers (in English), 12h/year, International Master's SIMOS, ENSGTI, Pau, France.
• E2 [K. Schmidmayer]: Coupled heat transfers, 12h/year, ENSGTI, Pau, France.
• E3 (M. David): Advanced physics (classes: 6h/year, labs: 5h/year) ENSGTI
• E1 (M. David): Modelling and simulation in fluid mechanics (lectures: 4h/year; classes: 16h/year). ENSGTI.
• E3 (M. Mehta):Modelling of energy systems (40.5 h/year). ENSGTI
• L1 (I. Lannabi): Descriptive statistics (22.5h/year, labs), Mathematics & MIASHS. University of Pau (UPPA).
• L1 (I. Lannabi) Mathematical Algorithms 1 and Python (49.5h/year, labs) Mathematics, University of Pau (UPPA).
• L2 (A. Bosco) Scientific computing (18h/year labs), computer science, UPPA.
• L1 MIASHS/L2 Natural sciences (A. Bosco) Descriptive statistics (22.5h/year labs), UPPA.

11.2.2 Supervision

• PhD in progress: Puneeth Bikkanahally Muni Reddy, “Modelling turbulent flows in natural convection regimes using hybrid RANS-LES approaches”, UPPA, ANR project Monaco_2025, Rémi Manceau.
• PhD in progress: Mahitosh Mehta, “Development of an agile methodology for hybrid RANS-LES computations of turbulent flows”, UPPA, E2S-UPPA Asturies project, Rémi Manceau
• PhD in progress: Romaric Simo Tamou, “Development of high-order methods in a Cartesian AMR/Cutcell code. Application to LES modelling of combustion”, IFPEN, E2S-UPPA Asturies project, Vincent Perrier.
• PhD in progress: Anthony Bosco, “Development of Fast, Robust and Accurate numerical methods for turbulence models on Complex Meshes” CEA/E2S-UPPA, E2S-UPPA Asturies project, Vincent Perrier and Jonathan Jung.
• PhD in progress: Alexis Ferré, “CFD and experimental study of a thermocline-type thermal storage for an optimized design and data entry of component scale models in the framework of a multi-scale approach”, CEA LITEN, Rémi Manceau.
• PhD in progress: Ibtissem Lannabi , “Discontinuous Galerkin methods for low Mach flows in fluid mechanics”, EDENE project (H2020 Marie-Sklodowska-Curie COFUND), Jonathan Jung and Vincent Perrier.
• PhD in progress: Esteban Coiffier, "Analyse et simulation numériques de discrétisations décalées en thermohydraulique diphasique", CEA-Saclay, Vincent Perrier & Jonathan Jung.

11.2.3 Juries

• Reviewer of the PhD thesis of J. Janin, Aix-Marseille university [R. Manceau]
• Reviewer of the PhD thesis of J. Cazé, Aix-Marseille university [V. Perrier]
• President of the jury for the PhD thesis of E. Rondeaux, university Paris-Saclay [R. Manceau]
• Member of the defense committee of the PhD thesis of A. Weppe, ENSMA [R. Manceau]
• Member of the defense committee of the PhD thesis of M. Carlsson, Chalmers Technical University, Sweden [R. Manceau]
• Member of the defense committee of the PhD thesis of S. Michel, Bordeaux University, France [V. Perrier]
• Reviewer and president of the defense committee of the HDR of S. Abide, Perpignan University [P. Bruel]

11.3.1 Interventions

39 J. Jung. Les mathématiques appliquées au service de la sureté nucléaire: Nuit européenne des chercheurs, château de Pau, 30th Sept. 2022.

Intervention about "scientists facing war" following the movie "Adventures of a Mathematician", adapted from the autobiography of Stan Ulam at Cinéma de Mourenx (Vincent Perrier).

40 J. Jung. Quelques applications de la recherche en mathématiques appliquées. 4th May 2022.

41 J. Jung. Quelques applications de la recherche en mathématiques appliquées. 6th May 2022.

42 I. Lannabi and J. Cresson. Village des sciences. 15th Oct. 2022.

43 I. Lannabi and I. Greff. Journée Maths et filles. 8th Dec. 2022.

44 R. Manceau. Prévoir l'imprévisible. Nuit Européenne des chercheur.e.s, Château de Pau. Pau, France, 30th Sept. 2022.

45 K. Schmidmayer. 'Les bulles de cavitation et leurs interventions inattendues en médecine'. In: Nuit Européenne des chercheur.e.s, Château de Pau. Pau, France, 30th Sept. 2022.

International journals

• 11 articleL.Luc Biasiori-Poulanges and K.Kevin Schmidmayer. A phenomenological analysis of droplet shock-induced cavitation using a multiphase modelling approach.Physics of Fluids35January 2023, 013312
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• 12 articleV.Vladimir Duffal, B.Benoît de Laage de Meux and R.Remi Manceau. Development and Validation of a new formulation of Hybrid Temporal Large Eddy Simulation.Flow, Turbulence and Combustion1082022, 42
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• 13 articleM.Mauro Grioni, P.Pascal Bruel, S. A.Sergio A Elaskar and A. E.Anibal E Mirasso. An application of the scale-adapted simulation to the unsteady flow across a tube bundle.International Journal of Heat and Fluid Flow962022, 109007
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• 14 articleJ.Jonathan Jung and V.Vincent Perrier. Steady low Mach number flows: identification of the spurious mode and filtering method.Journal of Computational PhysicsJuly 2022, 111462
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• 15 articleG.Gustave Sporschill, F.Flavien Billard, M.Michel Mallet, R.Remi Manceau and H.Hervé Bézard. Assessment of Reynolds-Stress models for aeronautical applications.International Journal of Heat and Fluid Flow962022
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National peer-reviewed Conferences

• 16 inproceedingsM.Mauro Grioni, S.Sergio Elaskar, P.Pascal Bruel and A.Anibal Mirasso. Comparación de algoritmos de acoplamiento velocidad-presión para problemás no estacionarios del flujo alrededor de un cilindro circular.2022 IEEE Biennial Congress of Argentina (ARGENCON)San Juan, ArgentinaIEEESeptember 2022
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Conferences without proceedings

• 17 inproceedingsA.Anthony Bosco and V.Vincent Perrier. Discontinuous Galerkin method for the simulation of axisymmetric compressible flows.HONOM 2022 - European Workshop on High order nonlinear numerical methods for evolutionary PDEs: Theory and Applications,Braga, FranceApril 2022
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• 18 inproceedingsA.Anthony Bosco, V.Vincent Perrier and J.Jonathan Jung. Discontinuous Galerkin method for the computation of axisymmetric flows.ECCOMAS CONGRESS 2022 8th European Congress on Computational Methods in Applied Sciences and EngineeringOslo, NorwayJune 2022
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• 19 inproceedingsA.Anthony Bosco and V.Vincent Perrier. Méthodes numérique d'ordre élevé pour la turbulence..Journée du LRC Anabase avec MARGAUxTalence, FranceDecember 2022
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• 20 inproceedingsA.Alexis Ferré, R.Remi Manceau, S.Sylvain Serra, J.Jérôme Pouvreau and A.Arnaud Bruch. Etude CFD de l'impact des conditions d'injection pour un stockage thermocline en eau.Congrès de la Société Française Thermique SFTValenciennes, FranceMay 2022
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• 21 inproceedingsS. K.Sofen Kumar Jena, P.Puneeth Bikkanahally and R.Remi Manceau. Numerical simulation of a turbulent natural convection flow in a cubic cavity with centrally placed partially heated inner obstacle.3rd high-fidelity industrial LES/DNS symp. (HiFiLeD)Brussels, BelgiumDecember 2022
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• 22 inproceedingsJ.Jonathan Jung, V.Vincent Perrier and I.Ibtissem Lannabi. On low Mach number fixes for Roe-type schemes.Rencontres de la thermohydraulique numérique du CEA/STMFSaint-Rémy-lès-Chevreuse, FranceJune 2022
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• 23 inproceedingsJ.Jonathan Jung and V.Vincent Perrier. Relations between the low Mach number problem and the long time limit of the wave system.HONOM 2022 - European Workshop on High order nonlinear numerical methods for evolutionary PDEs: Theory and ApplicationsBraga, PortugalApril 2022
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• 24 inproceedingsJ.Jonathan Jung and V.Vincent Perrier. Relations between the low Mach number problem and the long time limit of the wave system.Rencontres de la thermohydraulique numérique du CEA/STMFSaint-Rémy-lès-Chevreuse, FranceJune 2022
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• 25 inproceedingsF.Franck Mastrippolito, R.Remi Manceau and P.Pascal Bruel. Modélisation des effets de giration pour les jets en écoulement transverse.Journée thématique SFT : Aérothermique des systèmes propulsifs pour l’aéronautiqueParis, FranceOctober 2022
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• 26 inproceedingsM.Mahitosh Mehta, R.Remi Manceau, V.Vladimir Duffal and B.Benoit de Laage de Meux. An active hybrid RANS/LES approach for grey area mitigation.DLES13 - Direct and Large Eddy SimulationUdine, ItalyOctober 2022
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• 27 inproceedingsV.Vincent Perrier. Derivation of models and numerical methods for homogenized multiphase flows based on stochastic ideas.ECCOMAS CONGRESS 2022 8th European Congress on Computational Methods in Applied Sciences and EngineeringOslo, NorwayJune 2022
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• 28 inproceedingsV.Vincent Perrier and K.Kevin Schmidmayer. A multiscale numerical scheme for the simulation of dispersed multiphase flows.MultiMat 2022 - 10th International Conference on Numerical Methods for Multi-Material Fluid FlowZürich, SwitzerlandAugust 2022
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• 29 inproceedingsV.Vincent Perrier. Stochastic derivation of models and numerical methods for multiphase compressible flows.34ème Séminaire sur la mécanique des fluides numériqueParis, FranceJanuary 2022
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• 30 inproceedingsK.Kevin Schmidmayer, J.Joris Cazé, F.Fabien Petitpas, E.Eric Daniel and N.Nicolas Favrie. Modelling interactions of waves with diffused interfaces.MultiMat 2022 - 10th International Conference on Numerical Methods for Multi-Material Fluid FlowZürich, SwitzerlandAugust 2022
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• 31 inproceedingsK.Kevin Schmidmayer. Droplet shock-induced cavitation using a multiphase modelling approach.Sorbonne University Seminar, Pierre and Marie Curie Campus, Institut Jean le Rond d’AlembertParis, FranceDecember 2022
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• 32 inproceedingsK.Kevin Schmidmayer. Droplet shock-induced cavitation using a multiphase modelling approach.LMAP seminarPau, FranceJanuary 2023
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• 33 inproceedingsK.Kevin Schmidmayer. Modeling and simulation of bubble dynamics in the diffuse-interface framework.Workshop on Cavitation, bubble dynamics and mass transferStrasbourg, FranceMay 2022
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• 34 inproceedingsK.Kevin Schmidmayer. Modeling and simulation of bubble dynamics in the diffuse-interface framework.ETH Zürich seminarZürich, SwitzerlandAugust 2022
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• 35 inproceedingsS.Sangeeth Simon, V.Vincent Perrier, J.Jonathan Jung and M.Matthieu Haefele. A task-based parallelization of a finite volume code for hyperbolic conservation law.33rd parallel CFD International conferenceAlba, ItalyMay 2022
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• 36 inproceedingsS.Sangeeth Simon, V.Vincent Perrier, J.Jonathan Jung and M.Matthieu Haefele. Design And Analysis Of Task-based Parallelization Of A Discontinuous Galerkin Euler Flow Solver On Heterogeneous Architectures.ECCOMAS CONGRESS 2022 8th European Congress on Computational Methods in Applied Sciences and EngineeringOslo, NorwayJune 2022
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Other scientific publications

• 37 inproceedingsI.Ibtissem Lannabi, J.Jonathan Jung and V.Vincent Perrier. Low Mach number flows: a cure to checkerboard modes.Sixteenth International Conference on Mathematics and its ApplicationsJaca, SpainSeptember 2022
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• 38 inproceedingsI.Ibtissem Lannabi, J.Jonathan Jung and V.Vincent Perrier. Low Mach number flows: a cure to checkerboard modes.New trends in complex flowsParis, FranceSeptember 2022
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Scientific popularization

• 39 miscJ.Jonathan Jung. Les mathématiques appliquées au service de la sureté nucléaire: Nuit européenne des chercheurs, château de Pau,.September 2022
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• 40 miscJ.Jonathan Jung. Quelques applications de la recherche en mathématiques appliquées.May 2022
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• 41 miscJ.Jonathan Jung. Quelques applications de la recherche en mathématiques appliquées.May 2022
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• 42 miscI.Ibtissem Lannabi and J.Jacky Cresson. Village des sciences.October 2022
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• 43 miscI.Ibtissem Lannabi and I.Isabelle Greff. Journée Maths et filles.December 2022
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• 44 miscR.Remi Manceau. Prévoir l'imprévisible.September 2022
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• 45 inproceedingsK.Kevin Schmidmayer. Les bulles de cavitation et leurs interventions inattendues en médecine.Nuit Européenne des chercheur.e.s, Château de PauPau, FranceSeptember 2022
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Educational activities

• 46 unpublishedR.Remi Manceau. Codes de calcul industriels pour la simulation des écoulements turbulents.February 2022, MasterFrance
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• 47 unpublishedR.Remi Manceau. Industrial codes for CFD.February 2022, MasterFrance
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