Suppression of wall modes in rapidly rotating Rayleigh-B\'enard convection by narrow horizontal fins

The heat transport by rapidly-rotating Rayleigh-B\'enard convection is of fundamental importance to many geophysical flows. Laboratory measurements are impeded by robust wall modes which develop along vertical walls, significantly perturbing the heat flux. We show that narrow horizontal fins along the vertical walls efficiently suppress wall modes ensuring that their contribution to the global heat flux is negligible compared with bulk convection in the geostrophic regime, thereby paving the way for new experimental studies of geophysically relevant regimes of rotating convection.Comment: 6 pages, 6 figure

Skapande av en uppsättning verktyg som möjliggör snabba systemteknikslingor för små återanvändbara bärraketer

The 2010's have seen many changes happening in the launcher world: private players have emerged increasing competition for the traditional launch operators and the development of reusable launcher allowing a decrease in launch cost. The satellite market has also evolved with the appearance of nano-satellites and the development of satellite constellations. ArianeWorks is a joint initiative between CNES and ArianeGroup aiming at accelerating European innovation in the launcher field. Within this framework, Themis, a reusable first stage demonstrator, is currently built and tested. This thesis presents the evaluation of a mini-launcher that would use a derivative of Themis as a first stage. To do so, a set of software tools has been developed and evaluated. These tools make it possible to evaluate various launcher architectures, and to carry out system loops in order to refine the design choices and associated performances. The first results of design and performance from the tools are also presented.Under 2010-talet har många förändringar skett i bärraketvärlden: privata aktörer har dykt upp och ökad konkurrensen för de traditionella operatörerna. Utvecklingen av återanvändbara bärraketer möjliggör en minskning av uppskjutningskostnaden. Satellitmarknaden har också utvecklats med uppkomsten av nanosatelliter och utvecklingen av satellitkonstellationer. ArianeWorks är ett gemensamt initiativ mellan CNES och ArianeGroup som syftar till att påskynda europeisk innovation inom bärraketområdet. Inom detta ramverk byggs och testas för närvarande Themis, en återanvändbar demonstrator för ett första raketsteg. Den här uppsatsen presenterar utvärderingen av en ministartare som använder en del av Themis. Inom detta arbetet har en uppsättning mjukvaruverktyg utvecklats och utvärderats. Dessa verktyg gör det möjligt att utvärdera olika bärraketutformningar och utföra systemloopar för att förfina utformningsval och tillhörande prestanda. De första resultaten av utformningen och prestandan presenteras

Skapande av en uppsättning verktyg som möjliggör snabba systemteknikslingor för små återanvändbara bärraketer

The 2010's have seen many changes happening in the launcher world: private players have emerged increasing competition for the traditional launch operators and the development of reusable launcher allowing a decrease in launch cost. The satellite market has also evolved with the appearance of nano-satellites and the development of satellite constellations. ArianeWorks is a joint initiative between CNES and ArianeGroup aiming at accelerating European innovation in the launcher field. Within this framework, Themis, a reusable first stage demonstrator, is currently built and tested. This thesis presents the evaluation of a mini-launcher that would use a derivative of Themis as a first stage. To do so, a set of software tools has been developed and evaluated. These tools make it possible to evaluate various launcher architectures, and to carry out system loops in order to refine the design choices and associated performances. The first results of design and performance from the tools are also presented.Under 2010-talet har många förändringar skett i bärraketvärlden: privata aktörer har dykt upp och ökad konkurrensen för de traditionella operatörerna. Utvecklingen av återanvändbara bärraketer möjliggör en minskning av uppskjutningskostnaden. Satellitmarknaden har också utvecklats med uppkomsten av nanosatelliter och utvecklingen av satellitkonstellationer. ArianeWorks är ett gemensamt initiativ mellan CNES och ArianeGroup som syftar till att påskynda europeisk innovation inom bärraketområdet. Inom detta ramverk byggs och testas för närvarande Themis, en återanvändbar demonstrator för ett första raketsteg. Den här uppsatsen presenterar utvärderingen av en ministartare som använder en del av Themis. Inom detta arbetet har en uppsättning mjukvaruverktyg utvecklats och utvärderats. Dessa verktyg gör det möjligt att utvärdera olika bärraketutformningar och utföra systemloopar för att förfina utformningsval och tillhörande prestanda. De första resultaten av utformningen och prestandan presenteras

Suppression of wall modes in rapidly rotating Rayleigh-Bénard convection by narrow horizontal fins

The heat transport by rapidly-rotating Rayleigh-Bénard convection is of fundamental importance to many geophysical flows. Laboratory measurements are impeded by robust wall modes which develop along vertical walls, significantly perturbing the heat flux. We show that narrow horizontal fins along the vertical walls efficiently suppress wall modes ensuring that their contribution to the global heat flux is negligible compared with bulk convection in the geostrophic regime, thereby paving the way for new experimental studies of geophysically relevant regimes of rotating convection

SuperRail - Premier câble supraconducteur au monde à être installé sur un réseau ferré à usage commercial

PosterNational audienceLe réseau ferroviaire français est soumis à de nombreuses contraintes, notamment liées à l'augmentation du trafic de 60% entre 1998 et 2008 et qui devrait encore augmenter de 4 fois d'ici 2030. Pour renforcer les capacités de transport en ville tout en réduisant les pertes électriques, il peut être intéressant d'installer des câbles supraconducteurs. C’est le choix retenu par la SNCF dans le cadre du projet SuperRail, lancé en février 2022 et qui consiste en le développement, la fabrication et l'installation de câbles supraconducteurs à haute température critique (HTc) pour renforcer l'alimentation électrique de la gare Montparnasse à Paris. Deux câbles HTc de 1,5 kV-3,5 kA et 80 m de long seront installés en parallèle et reliés à la sous-station électrique de Ouest-Ceinture pour alimenter deux faisceaux de voies. Dans cet article, nous détaillerons les innovations mises en œuvre dans le cadre de ce projet, notamment : le câble supraconducteur, les terminaisons et le système de refroidissement fournissant 2 kW à 68 K. Pour finir, des études prospectives visant à améliorer davantage l’efficacité énergétique du système en optimisant ou remplaçant certains éléments seront présentées

Test results of the SuperRail HTS cable system for the French railway electric grid

PosterInternational audienceThe SuperRail project, backed by the French government, will be the first installation of a high-temperature superconducting (HTS) cable system on a commercially operated railway electric grid. The project's goal is to develop, manufacture, and install a HTS DC cable system at the Montparnasse railways station in Paris. Due to the restricted space available in the city's saturated underground, the HTS technology provides the only viable solution for increasing the power supply from the railway substation to a group of railway tracks. This will allow for an increase in train traffic while simultaneously reducing CO2 emissions. Two 80 m long 1.5 kV-3.5 kA HTS DC cables made of 2G conductors will be installed in parallel. They are designed to meet stringent load chart requirements and to sustain a 67 kA-200 ms short-circuit current. Prior to the installation at Montparnasse, a complete 35-m HTS cable type test loop was successfully installed and tested at the SNCF Vitry test facility. This system includes two terminations, one splice, and a fully automated cooling system that manages the thermal cycles between room temperature and cryogenic rated conditions

SuperRail - World-first HTS cable to be installed on a commercial railway network in France

Large scale oral sessionsInternational audienceThis paper presents the SuperRail project, launched in June 2022 and consisting in the development, the manufacturing and the installation of a high temperature superconducting HTS DC cable system. The objectives of the project are to reinforce the power supply of the Montparnasse railways station in Paris, to increase the traffic and to participate to the reduction of CO2 emission. The saturated underground in the centre of Paris does not allow to create new right of ways and only the HTS cable technology allows to carry the required power to railway tracks using the few available 100 mm ducts left. The cable system and the ancillary services have to answer to a load chart with a high level of requirements corresponding to the connection of a standard supply cell in a substation to a group of railways tracks in very constraints areas. The technologies developed have the potential to be reproduced in similar cases existing in large cities. In the case of SuperRail, two 80 m long 1.5 kV-3.5 kA HTS DC cables made of 2G conductors will be installed in parallel. They will need to sustain a 67 kA-200 ms short-circuit current. The cryogenic system to cool the HTS cables is specifically designed for this project. It is based on a Reverse Turbo-Brayton cycle providing cooling power of about 2 kW at 67 K. This system intends to ensure low maintenance during life cycle, high reliability and would be scalable for future application (unlimited to railway). Efforts are being done to reduce the losses in the 4 current leads, and to optimize the space required by the pipes for the circulation of the liquid nitrogen. In parallel, prospective studies are being carried out in order to find original solutions to replace the current leads by other systems integrating a part of the power converter and the transformer at cryogenic temperature. SuperRail is a landmark project, as it is the first time that a DC HTS cable system is installed on a commercially operated railway network

SuperRail − World-first HTS cable to be installed on a railway network in France

We would like to thank our colleagues at SNCF, Nexans, Absolut System, University Paris-Saclay and the University of Lorraine for the valuable insights they provided and the in-depth discussions we had.The SuperRail project consists in the development, manufacturing, installation and long-term operation of a high temperature superconducting (HTS) DC cable system for railway applications. The objectives of the project are to reinforce the power supply of the Montparnasse railway station in Paris, to increase the traffic and to participate to the reduction of CO2 emission. The saturated underground in the center of Paris does not allow to create new right of ways and only the HTS cable technology allows to carry the required power to railway tracks using the few available 100 mm conduits left. The HTS cable system must answer to a load chart with a high level of requirements corresponding to the connection of a substation to a set of railways tracks in very constraints areas. In the case of SuperRail, two 60-meter long 1.5 kV-3.5 kA HTS DC cables made of second-generation (2G) conductors will be installed in parallel. They need to sustain a 67 kA-200 ms short-circuit current. The cryogenic system is specifically designed for this project. It is based on a Reverse Turbo-Brayton cycle producing cooling power of about 1700 W at 67 K. This system intends to ensure low maintenance during life cycle, high reliability and would be scalable for future application (not limited to railways). In parallel, prospective studies are being carried out to simulate superconducting cables in railway networks, and to find original solutions to replace the current leads. SuperRail is a landmark project, as it is the first time that a DC HTS cable system is installed on a commercially operated railway network. The technologies developed have the potential to be reproduced in similar cases existing in large cities

Spallation study with proton beams around 1 GeV: Neutron production

Experiments performed at Lab. Nat. SATURNE on neutron produced by spallation from proton beams in the range 0.8 - 1.6 GeV are presented. Experimental data compared with codes show a significant improvement of the recent intra-nuclear cascade (J. Cugnon). This is also true in the same way for the neutron production from thick targets. However the model underestimates the energetic neutrons produced in the backward direction and other quantities as residual nuclei cross sections are not accurately predicted.SCOPUS: ar.jinfo:eu-repo/semantics/publishe