210 research outputs found
Apports des méthodes fréquentielle et temporelle dans l'étude des instabilités de frottement responsables du crissement
International audienceIn order to model and understand friction-induced vibration phenomenon, two approaches are compared in this article: temporal approach and modal approach. This analysis has been made on a simplified system composed of two beams in contact. Modal approach consists in calculating eigenvalues of the friction coupled system. Instabilities appear when a pair of modes merges. Eigenvalues with positive real parts are identified as potentially unstable modes. Temporal approach calculates the evolution of displacements, velocities, accelerations, forces ... One speaks about instabilities when stick or separation zones appear in the contact surfaces. With this approach frequencies which are excited during instability are obtained. Results have been compared and both methods give coherent and complementary results
Friction-induced instabilities: modal, transient analysis and experimental validation
International audienceThe vibrations generated at the interface between the two bodies in friction are responsible for various noises such as squealing, juddering, hammering, hooting, etc. In order to model and understand friction-induced vibration phenomenon, two types of analysis, modal analysis and transient analysis, are compared in this article. This study has been made on a simplified system composed of two beams in contact. In modal analysis, instabilities appear when a pair of modes merges. Eigenvalues with positive real parts are identified as potentially unstable modes. In transient analysis, one speaks about instabilities when stick or separation zones appear in the contact surfaces. Results have been compared and both analysis give coherent and complementary results. An experimental validation has been made and shows a good correlation between experimental and numerical results
Use of green roofs to solve storm water issues at the basin scale – Study in the Hauts-de-Seine County (France)
International audienceAt the building scale, green roof has demonstrated a positive impact on urban runoff (decrease in the peak discharge and runoff volume). This work aims to study if similar impacts can be observed at basin scale. It is particularly focused on the possibility to solve some operational issues caused by storm water.For this purpose, a methodology has been proposed. It combines: a method to estimate the maximum roof area that can be covered by green roof, called green roofing potential, and an urban rainfall-runoff model able to simulate the hydrological behaviour of green roof.This methodology was applied to two urban catchments affected one by flooding and the other one by combined sewage overflow. The results show that green roof can reduce the frequency and the magnitude of such problems depending on the covered roof surface. Combined with other infrastructures, they represent an interesting solution for urban water management
Mesures météorologiques, hydrologiques et glaciologiques sur le glacier du Zongo : année hydrologique 1998-99
Mesures météorologiques, hydrologiques et glaciologiques sur le glacier du Zongo : année hydrologique 2000-2001
Mesures météorologiques, hydrologiques et glaciologiques sur le glacier du Zongo : année hydrologique 2001-2002
Single-particle fluctuations and directional correlations in driven hard-sphere glasses
Addition of tabulated equation of state and neutrino leakage support to IllinoisGRMHD
We have added support for realistic, microphysical, finite-temperature
equations of state (EOS) and neutrino physics via a leakage scheme to
IllinoisGRMHD, an open-source GRMHD code for dynamical spacetimes in the
Einstein Toolkit. These new features are provided by two new, NRPy+-based
codes: NRPyEOS, which performs highly efficient EOS table lookups and
interpolations, and NRPyLeakage, which implements a new, AMR-capable neutrino
leakage scheme in the Einstein Toolkit. We have performed a series of strenuous
validation tests that demonstrate the robustness of these new codes,
particularly on the Cartesian AMR grids provided by Carpet. Furthermore, we
show results from fully dynamical GRMHD simulations of single unmagnetized
neutron stars, and magnetized binary neutron star mergers. This new version of
IllinoisGRMHD, as well as NRPyEOS and NRPyLeakage, is pedagogically documented
in Jupyter notebooks and fully open source. The codes will be proposed for
inclusion in an upcoming version of the Einstein Toolkit.Comment: 20 pages, 9 figures. v2 matches PRD versio
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