The 4th Mmg day will be held in memoriam of Cécile Dobrzynski on 17th December.
It will take place at:
Amphi Charpak (LPNHE, tower 22)*,
Jussieu campus,
4 place Jussieu,
75005 Paris (France).
*access map below
The registration is free, but desired: https://www.mmgtools.org/mmg-day-2019-in-memoriam-of-c-dobrzynski-subscription-form (If you have issue with the embedded form you can use this direct link, note that you will not receive subscription confirmation).
The purpose of this day is to focus on Cecile’s collaborators and on subjects of interest to her.
Speakers
Perle Geoffroy-Donders, Postdoctoral Researcher at CNRS – PIMM
Méthode de déshomogénéisation en optimisation de formes présentant une microstructure pseudo-périodique.
Bruno Levy, Inria Research Director – Head of the Inria Nancy Grand-Est research center
Simulation de fluides Navier-Stokes à surface libre à l’aide du transport optimal semi-discret.
Cécile Dobrzynski s’intéressait à la simulation de phénomènes physiques à l’aide de maillages adaptatifs, domaine dans lequel elle a proposé des contributions majeures. Chercheuse passionnée, intéressée à la fois par des aspects mathématiques et par le développement logiciel, elle laisse derrière elle un important héritage scientifique et technique, et des contributions majeures dans un logiciel (mmg3d) très largement utilisé, dont elle a été la pierre (ou plutôt le tétraèdre !) angulaire.
Je parlerai aujourd’hui d’une méthode Lagrangienne de simulation de fluides, due à Thomas Gallouet et Quentin Mérigot, qui aurait sans doute intéressé Cécile parcequ’elle conduit naturellement à un maillage adaptatif qui suit la simulation, et aussi parceque l’algorithmique sous-jacente tombe dans ses sujets de prédilection (triangulations 3D, intersection de maillages).
Dans cette méthode, le fluide est représenté par un diagramme de Voronoi généralisé (diagramme de Laguerre). La méthode consiste à déterminer les paramètres du diagramme de Laguerre de manière à prescrire le volume des cellules. Ensuite, un schéma Euler implicite permet d’ingégrer la viscosité. Si l’on souhaite représenter des fluides à surface libre, ceci revient à changer un tout petit peu la définition du diagramme de Laguerre. Il est ensuite assez facile de modéliser la tension de surface. Je montrerai quelques résultats d’expériences numériques.
Vincent Moureau, Research fellow at CNRS – CORIA
Application of the MMG library to the parallel and dynamic isotropic mesh adaptation of moving material interfaces.
Thanks to the steady growth of computational resources, Large-Eddy Simulation (LES) of realistic systems has become attainable. In these systems, the presence of turbulent multi-physics flows involves a large range of scales. Some of these scales need to be resolved by the mesh to capture the proper flow dynamics. This is particularly true for material interfaces such as premixed flames and gas/liquid interfaces. Adaptive or dynamic mesh adaptation (AMR) is an appealing technique to reduce the modeling errors at the interface location. AMR of tetrahedral-based meshes is difficult to perform as it requires numerous mesh topology changes. It is even more challenging for LES as high-quality grids are required to resolve the turbulent scales that are close to the cut-off frequency of the mesh. The use of finite-volume schemes also imposes a strong constraint on the mesh quality. A parallel AMR strategy has been developed recently (Bénard et al., IJNMF 2016) in the YALES2 flow solver (www.coria-cfd.fr). It combines adaptation and repartitioning steps to enable the AMR of massive grids counting billion cells exploiting up to tens of thousand cores. Mesh adaptation relies on the work of Dapogny et al. (JCP 2014) available in the MMG library (www.mmgtools.org). The presentation will focus on the parallel adaptation strategy for both volume and surface meshes, its optimization on modern super-computers and on various academic and industrial applications related to turbulent combustion and primary atomization.
Olivier Pironneau, Professor emeritus at UPMC – LJLL
Jean-François Remacle, Professor at Louvain School of Engineering – UCL
Robust and fast construction of quad layouts.
In this presentation, we will present an efficient way of producing quad layouts i.e. partitioning of an object’s surface into simple networks of conforming quadrilateral patches. Our approach is a variant of the mixed integer approach of D. Bommes and his co-authors [1] that does not rely on an integer grid. Here, the solution of one single minimization problem with linear constraints allows to construct the layout.
[1] Bommes, D., Zimmer, H., & Kobbelt, L. (2009). Mixed-integer quadrangulation. ACM Transactions On Graphics (TOG), 28(3), 77.
Program
10h00 – 10h15 : Introduction speech, R. Abgrall, H. Beaugendre, M. Ricchiuto
10h30 – 12h00 : Presentations
Lunch time
14h00 – 17h00 : Presentations
Important dates
December 10 – subscription deadline
December 16 – 14h00 : Holding of the Mmg councils (consortium members only)
Access map
[gview file=”https://www.mmgtools.org/files/2019/07/0-Plan_acces_amphi-Charpak-LPNHE-2016_10_20.pdf”]
