Contributions à la simulation numérique des écoulements fluides : exemples en milieu poreux et en aéronautique

L’essentiel de mes travaux scientifiques portent sur la simulation numérique de phénomènes complexes. Leurs caractéristiques communes peuvent se regrouper autour de trois axes principaux : l’étude de simulations non seulement réalistes mais réelles; l’utilisation de modèles multi-physiques et le couplage de méthodes numériques variées adaptées aux problèmes abordés. Cette stratégie a été appliquée à deux domaines d’application distincts : la modélisation et la simulation numérique d’écoulements en milieu poreux et la modélisation et simulation numérique en aéronautique

Parametric Studies of Flat Plate Trajectories Using VIC and Penalization

International audienceFlying debris is generated in several situations: when a roof is exposed to a storm, when ice accretes on rotating wind turbines, or during inflight aircraft deicing. Four dimensionless parameters play a role in the motion of flying debris. The goal of the present paper is to investigate the relative importance of four dimensionless parameters: the Reynolds number, the Froude number, the Tachikawa number, and the mass moment of inertia parameters. Flying debris trajectories are computed with a fluid-solid interaction model formulated for an incompressible 2D laminar flow. The rigid moving solid effects are modelled in the Navier-Stokes equations using penalization. A VIC scheme is used to solve the flow equations. The aerodynamic forces and moments are used to compute the acceleration and the velocity of the solid. A database of 64 trajectories is built using a two-level full factorial design for the four factors. The dispersion of the plate position at a given horizontal position decreases with the Froude number. Moreover, the Tachikawa number has a significant effect on the median plate position

Extention of SU2 CFD capabilities to 3D aircraft icing simulation

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A positivity-preserving scheme for the aircraft icing droplet equations within SU2

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Combined finite element - particles discretisation for simulation of transport-dispersion in porous media

International audienceCombining finite element together with particle methods provide one of the best compromise for solving transport problem in porous media. Saturated or non-saturated flows are determined by boundary condition and the media permeability.\footnote{This work was partially supported by GDR MOMAS-CNRS} For real terrain, permeability can consist in various almost constant and imbricated zones with complex shapes. Thus, it is of some interest that the boundary between two adjacent zones coincides with a natural mesh interface and that each element is entirely contains in one such zone. Beside this, solving transport equation by means of particle methods offers two distinctive advantages. The method is unconditionally stable when applied to a pure convective equation, and it does not contain any numerical diffusion if the particle trajectories are correctly computed. Therefore the combination of finite elements and particle method appears to be a straightforward application of the principle : "the right method at the right place"

Accuracy Assessment of Li-ion Batteries Internal Resistance Model Through CFD Simulations, Experimental Measurements And Uncertainties

International audienceInternal resistance is a critical parameter of the thermal behavior of Li-ion battery cells. This paper proposes an innovative way to deal with the uncertainties related to this physical parameter using experimental data and numerical simulation. First, a CFD model is validated against an experimental configuration representing the behavior of heated Li-ion battery cells under constant discharging current conditions. Secondly, an Uncertainty Quantification based methodology is proposed to represent the internal resistance and its inherent uncertainties. Thanks to an accurate and fast to compute surrogate model, the impact of those uncertainties on the temperature evolution of Li-ion cells is quantified. Finally, a Bayesian inference of the internal resistance model parameters using experimental measurements is performed, permitting to reduce the prediction uncertainty by almost 95% for some temperatures of interest

Construction of a pp-adaptive continuous Residual Distribution scheme

A \textit{p}-adaptive continuous Residual Distribution scheme is proposed in this paper.Under certain conditions, primarily the expression of the total residual on a given element $K$ into residuals on the sub-elements of $K$ and the use of a suitable combination of quadrature formulas,it is possible to change locally the degree of the polynomial approximation of the solution.The discrete solution can then be considered non continuous across the interface of elements of different orders, while the numerical scheme still verifies the hypothesis of the discrete Lax-Wendroff theorem which ensures its convergenceto a correct weak solution.We detail the theoretical material and the construction of our \textit{p}-adaptive method in the frame of a continuous Residual Distribution scheme. Different test cases for non-linear equations at different flow velocities demonstrate numerically the validity of the theoretical results

Topological Data Analysis for numerical method comparisons of 2D turbulent flows

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Data-driven wall models for Reynolds Averaged Navier-Stokes simulations

International audienceThis article presents a data-based methodology to build Reynolds-Averaged Navier-Stokes (RANS) wall models for aerodynamic simulations at low Mach numbers. Like classical approaches, the model is based on nondimensional local quantities derived from the wall friction velocity u τ , the wall viscosity µ w , and the wall density ρ w. A fully-connected neural network approximates the relation u + = f (y + , p +). We consider reference data (obtained with RANS simulations based on fine meshes up to the wall) of attached turbulent flows at various Reynolds numbers over different geometries of bumps, covering a range of wall pressure gradients. After training the neural networks on a subset of the reference data, the paper assesses their ability to accurately recover data for unseen conditions on meshes that have been trimmed from the wall up to an interface height where the learned wall law is applied. The network's interpolation and extrapolation capabilities are quantified and carefully examined. Overall, when tested within its interpolation and extrapolation capabilities, the neural network model shows good robustness and accuracy. The global error on the skin friction coefficient is a few percent and behaves consistently over all the considered test cases

Contributions à la simulation numérique des écoulements fluides : exemples en milieu poreux et en aéronautique

L’essentiel de mes travaux scientifiques portent sur la simulation numérique de phénomènes complexes. Leurs caractéristiques communes peuvent se regrouper autour de trois axes principaux : l’étude de simulations non seulement réalistes mais réelles; l’utilisation de modèles multi-physiques et le couplage de méthodes numériques variées adaptées aux problèmes abordés. Cette stratégie a été appliquée à deux domaines d’application distincts : la modélisation et la simulation numérique d’écoulements en milieu poreux et la modélisation et simulation numérique en aéronautique