BEGIN:VCALENDAR VERSION:2.0 PRODID:-//hacksw/handcal//NONSGML v1.0//EN CALSCALE:GREGORIAN BEGIN:VEVENT SUMMARY:Competition between fracture mechanisms in third generation advanced high strength steel sheets by Thibaut HEREMANS DTSTART:20250114 DTEND:20250114 DESCRIPTION: \; Au cours des dernières décennies\, le développement de tôles d'acier avancé à haute résistance (AAHR)\, destinées de l'industrie automobile\, a permis d'atteindre des niveaux supérieurs de de résistance tout en maintenant une ductilité adéquate\, et ce\, à faibles coûts de fabrication. Cependant\, ces tôles d'aciers ont montré une tendance à basculer du mode de rupture ductile conventionnel\, dominé par la coalescence de cavités\, vers d'autres modes de rupture\, tels que la localisation plastique macroscopique\, voire même la fissuration fragile intergranulaire. Motivée par les implications néfastes de telles transitions de mécanisme de rupture sur la formabilité et sur la résistance aux impacts\, une vaste campagne d'essais mécaniques a été menée sur des tôles minces d'AAHR de troisième génération\, dans le but d'induire des déformations\, jusqu'à rupture\, selon des modes de chargement variés. Dans ce travail\, plusieurs transitions de mode de rupture ont été observées : (i) basculement d’un endommagement ductile à une localisation plastique en traction uniaxiale lorsque la température d'essai dépasse 100°C\, (ii) basculement d’un endommagement ductile à une rupture fragile de type quasi-clivage sous triaxialité de contrainte accrue\, et (iii) un mode de rupture inhabituel alternant entre des zones d’endommagement ductile et des zones de (quasi-)clivage fragile\, organisées en un motif périodique de chevrons pointant dans la direction de fissuration.  \; Jury members : Prof. Pascal Jacques (UCLouvain\, Belgium)\, supervisor Prof. Aude Simar (UCLouvain\, Belgium)\, chairperson Prof. Renaud Ronsse (UCLouvain\, Belgium) Prof. Thomas Pardoen (UCLouvain\, Belgium) Dr. Astrid Perlade (ArcelorMittal Global R&\;D) Prof. Aude Simar (UCLouvain\, Belgium) Prof. Sébastien Allain (Mines Nancy\, France) Prof. Daniel Casellas (Eurecat\, Spain)  \; Visio conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_NTFiM2MzZGYtMmMwYi00ZjAwLWJkMmYtNDZkMDJkMTVhYWJk%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%22c39f65d6-1437-487e-b97b-9b0e69dd3cec%22%7d  \; LOCATION:Place des Sciences\, A.03 SCES\, \, Louvain-la-Neuve 1348\, BE DTSTAMP:20241222 UID:6768157aa50e7 END:VEVENT BEGIN:VEVENT SUMMARY:Large-Eddy Simulation of supersonic ejectors\, using a newly developed wall model by Romain DEBROEYER DTSTART:20250115 DTEND:20250115 DESCRIPTION:Wall-modeling in LES is of crucial importance to allow scale-resolving simulations of turbulent flows in industrial-scale devices. Numerous models were developed and validated for incompressible flows\, including the simple quasi-analytical model based on Reichardt formula to approximate the ``law of the wall’’ (which covers the laminar sublayer\, the transition region and the log layer). This work presents a new scaling of Reichardt formula to properly take into account strong compressibility effects in wall-modeled LES (wmLES). The newly developed wall-model is validated against wall-resolved LES (wrLES) on three adiabatic turbulent channel flow cases at moderate Reynolds number\, and with increasing Mach number: ranging from a quasi-incompressible regime at M=0.25 \; up to a supersonic regime at M=1.5. The wall-model is also used to perform wmLES of channel flow cases at high Reynolds number\, and the velocity profile is seen to match the expectations. The wall-model is then used to perform a high-fidelity wmLES of a rectangular supersonic air ejector\, using periodic boundary conditions in the spanwise direction. The results are compared to those obtained using a 2-D RANS simulation\, and also to those obtained experimentally in a setup with transparent side-walls (also used for flow visualization). The structure of the mixing layers is analyzed and the postprocessing tools using total exergy fluxes are presented. The discrepancies between the RANS simulation and LES results are explained using an analysis of the turbulent fluctuating contributions for both frameworks: those being resolved in our LES\; yet only modeled in RANS. Finally\, the design of a new cylindrical supersonic ejector experiment is presented\; which is really the design used for industrial applications. The characteristic curves are obtained experimentally. They are also compared to those obtained using axisymmetric RANS simulations. It is found that \; such RANS simulations allow to predict quite well the global behavior of the ejector\, in on- and off-design operations. We however observe large deviations between the experimental and numerical wall-pressure profiles. To gain additional insight into the flow physics\, and also help explain the observed differences\, a high-fidelity wmLES of the full ejector is performed for an operating point at the end of the on-design regime\, just before the critical point. The results of this simulation are presented\, and are also used to provide an explanation for the consistent underestimation of the wall-pressure profile in RANS simulations\, using an extension of the compound-choking theory.  \; Jury members : Prof. Yann Bartosiewicz \; (UCLouvain\, Belgium)\, supervisor Prof. Grégoire Winckelmans (UCLouvain\, Belgium)\, supervisor Prof. Hadrien Rattez (UCLouvain\, Belgium)\, chairperson Dr. Matthieu Duponcheel (UCLouvain\, Belgium) Dr. Koen Hillewaert (ULiège\, Belgium) Prof. Stephan Hickel (TUDelft\, Netherlands)  \; Visio conference link: https://teams.microsoft.com/l/meetup-join/19%3ameeting_NmI4ZmE1YjktZTA5ZC00MmQ2LWFhYmYtNWUzYjY2NDFjZGM5%40thread.v2/0?context=%7b%22Tid%22%3a%227ab090d4-fa2e-4ecf-bc7c-4127b4d582ec%22%2c%22Oid%22%3a%224c4311bf-2267-4d85-bc2f-39a89e94db6a%22%7d LOCATION:Place Sainte Barbe\, auditorium BARB 94\, \, Louvain-la-Neuve 1348\, BE DTSTAMP:20241222 UID:6768157aa50f3 END:VEVENT BEGIN:VEVENT SUMMARY:Nano-Geodynamics: Bridging Atomic Scale Mechanisms and Mantle Convection DTSTART:20250117 DTEND:20250117 DESCRIPTION: \; The primary geological phenomena that impact our planet's surface are now elucidated in the context of plate tectonics. However\, this planetary dynamic is not the norm when we examine the other terrestrial planets in our solar system. It is becoming increasingly evident that this is one of the prerequisites for the emergence of life on a planetary body. It is now understood that plate tectonics represents merely the surface manifestation of the extensive convection currents that stir the Earth's mantle\, enabling the dissipation of its internal heat. A primary objective of geodynamics is to describe this convection. The crucial variable is the viscosity of the mantle rocks. In situ\, these rocks are subjected to extreme pressure and temperature conditions\, and only deform at exceedingly slow strain-rates. Despite notable advancements in recent years in replicating these conditions in the laboratory\, they remain largely inaccessible to us. An alternative approach is to model the behavior of matter under these conditions. This is now feasible thanks to multiscale models that can describe the deformation mechanisms of mantle minerals at exceedingly high pressures\, down to the atomic scale. In particular\, we will present how the extremely low natural strain-rates compel us to conceptualize the mechanisms active in the mantle.  \; Speaker : \; Patrick CORDIER\, Université de Lille &\; Institut Universitaire de France\, France  \;  \;  \; LOCATION:Place Sainte Barbe\, auditorium BARB 92\, \, Louvain-la-Neuve 1348\, BE DTSTAMP:20241222 UID:6768157aa50fd END:VEVENT END:VCALENDAR