Étude numérique de la ventilation naturelle, mise en oeuvre d'un modèle fin dans une simulation de thermique du bâtiment

The building sector is the global largest energy consumer. To reduce environmental impact of buildings, passive tools must be developed. Still, air conditioning is increasingly used in the DROM-COM. The development of natural ventilation is essential to reverse this trend. Multizone models are not really suited for describing natural ventilation flows. Computational fluid dynamics (CFD) seem to be a promising way too model those flows.This thesis deals with the adaptation of a direct resolution of the Navier-Stokes equations code to describe airflows in buildings. The development, implementation and comparison of different types of pressure boundary conditions on the openings were required. The behavior of a room subjected to natural and mixed convection has been studied thanks to this work. To integrate this model into a building simulation, a “black box” object that transparently calls the CFD code on a remote server from a multizone environment has been developed. Partial cooling of the walls of a cavity subjected to natural convection has been simulated using this method.Le secteur du bâtiment est le plus gros consommateur d'énergie au niveau mondial. Pour en réduire l'impact environnemental, l'utilisation de solutions passives pour améliorer le confort est nécessaire. Malgré ce constat, la climatisation est de plus en plus utilisée dans les DROM-COM. Le développement de la ventilation naturelle est incontournable pour inverser cette tendance. Les méthodes multizones, modèles historiques de la simulation thermique du bâtiment, peinent à décrire ce type d'écoulement. Les modèles de mécanique des fluides numériques (MFN) sont prometteurs pour lever ce frein à l'utilisation de la ventilation naturelle.Ce manuscrit traite de l'adaptation d'un code de résolution directe des équations de Navier-Stokes à la description d'écoulements d'air dans le bâtiment. À cette fin, le développement, l'implémentation et la comparaison de différents types de conditions aux limites en pression sur les ouvertures ont été nécessaires. Ce travail nous a permis d'étudier le comportement d'une chambre soumise à de la convection naturelle et mixte. Pour intégrer ces développements à une simulation de bâtiment, nous avons développé un objet qui appelle le code de MFN sur un serveur de calcul distant depuis un environnement multizone de façon transparente. Le refroidissement partiel des murs d'une cavité soumise à de la convection naturelle a pu être simulé à l'aide de cette méthode

The Use of Cream in the Investigation of Human Error in Aviation Events: a Case Study

To investigate Human Factors issues of the Traffic Alert and Collision Avoidance System (TCAS), a part-task simulation has been conducted. The analysis method employed was based on the CREAM principles and included the following steps: Predictive analysis, Simulations, Data analysis, Retrospective analysis. The project called ARCADES , presented in this paper, concerns the errors identification and research of causes. The collective work based on CREAM is composed of four steps alternating between work in pairs and plenary session: the events identification and classification, consensus on the events to be analyzed, the retrospective analysis, and the mutual analysis. The work group was composed of pilots, controllers, investigators and Human Factors experts. The analysis was based on the data collected during the simulations: video recordings, questionnaires, audio recording of debriefing. Concerning the identification step, results show the interest of the clear distinction between causes and consequences, as it exists in CREAM. Indeed, it enables to bind the analysts to objectivity in the identification and the calling of the events. Inter-pairs variability remains important for the three scenarios studied. Participants agreed on the interest of the method concerning the search of causes. The method enables to pursue analyses more deeply and more exhaustively, results show that the method guides towards systemic causes. Results also emphasize the complementarity of different points of view and the interest of a collective approach

Segregating the Distinct Effects of Sedentary Behavior and Physical Activity on Older Adults' Cardiovascular Profile: Part 2-Isotemporal Substitution Approach.

The aim of the study was to provide an isotemporal substitution model to predict how changes in physical behavior may affect the cardiovascular parameters (CVPs) of older adults. Methods: Participants wore a thigh-mounted accelerometer for 7 days. Phenotype of the carotid, brachial, and popliteal artery was conducted using ultrasound. Isotemporal substitution was used to simulate the degree to which replacing 1 hour of physical behavior with another would affect CVP. Results: Substitution of sedentary behavior with Standing and sporadic moderate- to vigorous-intensity physical activity (MVPA accumulated in bouts <10 min) would reduce resting heart rate [−6.20 beats per minute (−12.1 to −0.22) and −3.72 beats per minute (−7.01 to −0.44), respectively]. Substitution of sedentary behavior with light-intensity physical activity would reduce carotid artery diameter [−0.54 mm (−1.00 to −0.07)]. Substitution of Standing with sporadic MVPA would increase popliteal artery diameter [1.31 mm (0.11 to 2.51)]. Conclusions: Our modeling suggests that an accumulation of MVPA bouts that are shorter than the recommended 10-minute minimum may still improve CVP, with lower intensity physical activity also influencing CVP. Our findings are a promising avenue for lifestyle interventions in older adults to reduce the aging effects on CVP for those who cannot engage or sustain sufficient MVPA

2-(2-Pyrid­yl)pyridinium (2,2′-bipyridine-κ2 N,N′)tetra­kis­(nitrato-κ2 O,O′)bis­muthate(III)

The structure of the title compound, (C10H9N2)[Bi(NO3)4(C10H8N2)], consists of 2-(2-pyrid­yl)pyridinium cations and anions [Bi(NO3)4(C10H8N2)]−. The Bi3+ ion lies on the twofold axis. It is coordinated by two nitro­gen atoms from one 2,2′-bipyridine ligand and eight oxygen atoms from four NO3 − anions. The disordered cation is positioned at the inversion centre. The [Bi(NO3)4(C10H8N2)]− anions and 2-(2-pyrid­yl)pyridinium cations are connected via N—H⋯O hydrogen bonds into chains. Moreover, these chains are further linked into a two-dimensional layered structure through π–π stacking inter­actions between bipyridine ligands along the c axis [centroid–centroid distance = 2.868 (4) Å]

Numerical study of natural ventilation, CFD model integration in a building thermal simulation.

Le secteur du bâtiment est le plus gros consommateur d'énergie au niveau mondial. Pour en réduire l'impact environnemental, l'utilisation de solutions passives pour améliorer le confort est nécessaire. Malgré ce constat, la climatisation est de plus en plus utilisée dans les DROM-COM. Le développement de la ventilation naturelle est incontournable pour inverser cette tendance. Les méthodes multizones, modèles historiques de la simulation thermique du bâtiment, peinent à décrire ce type d'écoulement. Les modèles de mécanique des fluides numériques (MFN) sont prometteurs pour lever ce frein à l'utilisation de la ventilation naturelle.Ce manuscrit traite de l'adaptation d'un code de résolution directe des équations de Navier-Stokes à la description d'écoulements d'air dans le bâtiment. À cette fin, le développement, l'implémentation et la comparaison de différents types de conditions aux limites en pression sur les ouvertures ont été nécessaires. Ce travail nous a permis d'étudier le comportement d'une chambre soumise à de la convection naturelle et mixte. Pour intégrer ces développements à une simulation de bâtiment, nous avons développé un objet qui appelle le code de MFN sur un serveur de calcul distant depuis un environnement multizone de façon transparente. Le refroidissement partiel des murs d'une cavité soumise à de la convection naturelle a pu être simulé à l'aide de cette méthode.The building sector is the global largest energy consumer. To reduce environmental impact of buildings, passive tools must be developed. Still, air conditioning is increasingly used in the DROM-COM. The development of natural ventilation is essential to reverse this trend. Multizone models are not really suited for describing natural ventilation flows. Computational fluid dynamics (CFD) seem to be a promising way too model those flows.This thesis deals with the adaptation of a direct resolution of the Navier-Stokes equations code to describe airflows in buildings. The development, implementation and comparison of different types of pressure boundary conditions on the openings were required. The behavior of a room subjected to natural and mixed convection has been studied thanks to this work. To integrate this model into a building simulation, a “black box” object that transparently calls the CFD code on a remote server from a multizone environment has been developed. Partial cooling of the walls of a cavity subjected to natural convection has been simulated using this method

Inscrivez-vous à la première journée d'étude organisée par le RJC-SHS-CAP

Le RJC-SHS-CAP organise sa première journée d'étude le jeudi 12 octobre 2023, à la Maison des Sciences de l'Homme de Paris-Saclay Intitulé « Santé et environnement : une approche par les corps et les pratiques physiques », cette journée vise à comprendre et analyser les interrelations entre la question des corps, de l’environnement. Elle sera structurée en trois temps forts, une session de communication, un travail en ateliers et une table ronde, et s’inscrira dans une démarche interdiscip..

Excitation of Tyre Vibrations due to Tyre/Road Interaction

Tyre/road noise is the main contributor to road traffic noise at speeds above 40 km/h for passenger cars and above 70 km/h for heavy trucks. Research has been carried out during the last thirty years in order to understand and quantify the generation mechanisms responsible for tyre/road noise. However, there is still substantial work remaining until tyre/road noise can be reduced substantially if at all. The work presented in this thesis concerns the modelling the tyre/roads interaction and the resulting vibrations of the tyre structure. The model is supposed to calculate the time varying forces when the road roughness is indenting the tyre tread during rolling. To achieve this, a contact model is developed, implemented and validated against measurements. The contact model is formulated in the time domain and considers a three-dimensional contact. An elastic half-space is used as a tool to describe the deformation of the tyre tread, and an iterative algorithm is utilised in order to solve the contact problem for each time step of the calculation. In parallel, an alternative quasi-three-dimensional contact model is also presented. Good agreement of calculated and measured tyre vibrations is found for different tyres and road surfaces. Additionally to the tyre vibrations air-pumping is included in the model in the form of the local deformations of the tyre tread due to road roughness indenting at the contact patch. The local deformation is believed to be a main contributor to tyre/road noise about 1 kHz. In this work, the local deformation is calculated from the deformation of the elastic half-space used for the contact problem. Preliminary qualitative results shows that the sound radiated due to local deformation dominates above 1-2 kHz whereas the sound radiated by the tyre structure vibrations dominates below 1-2 kHz. The model developed in this thesis is used to study the coupling between vibration pattern on the tyre and radiated sound. It is shown, that mainly the low order modes are contributing to the radiation and that the coupling between modes with respect to the radiated sound is essential

Study of Crossbar Tyres in Rolling Conditions

A correct description of the contact between a tyre and a road is a crucial step towards the understanding and the prediction of tyre/road noise using deterministic models. The present work is about the study of crossbar tyres of the passenger car type in rolling conditions. Measurements were made on a crossbar tyre loaded on a rotating drum and acceleration signals were recorded on the tyre structure for both the tangential and normal directions. The measurement situation was also modelled using a deterministic three-dimensional contact model. Comparisons between measurements and calculations show satisfactory results when it comes to pitching frequencies and global shapes of the acceleration signals. Another result is that it can be seen that moment excitation of the tyre structure by each block hitting the road at the leading edge can be an important generation mechanism to include in models

Excitation of Tyre Vibrations due to Tyre/Road Interaction

Tyre/road noise is the main contributor to road traffic noise at speeds above 40 km/h for passenger cars and above 70 km/h for heavy trucks. Research has been carried out during the last thirty years in order to understand and quantify the generation mechanisms responsible for tyre/road noise. However, there is still substantial work remaining until tyre/road noise can be reduced substantially if at all. The work presented in this thesis concerns the modelling the tyre/roads interaction and the resulting vibrations of the tyre structure. The model is supposed to calculate the time varying forces when the road roughness is indenting the tyre tread during rolling. To achieve this, a contact model is developed, implemented and validated against measurements. The contact model is formulated in the time domain and considers a three-dimensional contact. An elastic half-space is used as a tool to describe the deformation of the tyre tread, and an iterative algorithm is utilised in order to solve the contact problem for each time step of the calculation. In parallel, an alternative quasi-three-dimensional contact model is also presented. Good agreement of calculated and measured tyre vibrations is found for different tyres and road surfaces. Additionally to the tyre vibrations air-pumping is included in the model in the form of the local deformations of the tyre tread due to road roughness indenting at the contact patch. The local deformation is believed to be a main contributor to tyre/road noise about 1 kHz. In this work, the local deformation is calculated from the deformation of the elastic half-space used for the contact problem. Preliminary qualitative results shows that the sound radiated due to local deformation dominates above 1-2 kHz whereas the sound radiated by the tyre structure vibrations dominates below 1-2 kHz. The model developed in this thesis is used to study the coupling between vibration pattern on the tyre and radiated sound. It is shown, that mainly the low order modes are contributing to the radiation and that the coupling between modes with respect to the radiated sound is essential

Study of Crossbar Tyres in Rolling Conditions

A correct description of the contact between a tyre and a road is a crucial step towards the understanding and the prediction of tyre/road noise using deterministic models. The present work is about the study of crossbar tyres of the passenger car type in rolling conditions. Measurements were made on a crossbar tyre loaded on a rotating drum and acceleration signals were recorded on the tyre structure for both the tangential and normal directions. The measurement situation was also modelled using a deterministic three-dimensional contact model. Comparisons between measurements and calculations show satisfactory results when it comes to pitching frequencies and global shapes of the acceleration signals. Another result is that it can be seen that moment excitation of the tyre structure by each block hitting the road at the leading edge can be an important generation mechanism to include in models