Search results for "fluid"
showing 10 items of 5513 documents
Comparison of Flow Measurement by 4D Flow Magnetic Resonance Imaging and by Particles Image Velocimetry on Phantom of Abdominal Aortic Aneurysm
2016
International audience; Predicting the rupture of Aortic Aneurysms is a complex problem that interests, from several decades, many researchers. The works on this issue are very complex, involving both the study of mechanical behavior of the artery as the flow of blood. The Magnetic Resonance Imaging (MRI) technique allows to obtain anatomic information of the arteries, than the flow inside thereof. The goal of this study is an inter comparison betweenflow data from MRI and those obtained by Particle Image Velocimetry (PIV). An experimental device simulating hemodynamic circulation is used. Initially in order to validate the device, the flow in a cylindrical glass tube is measured by these t…
Modeling by the finite element method of acoustic radiation in waveguides lined with locally or non locally reacting absorbent materials in the prese…
2011
Our concern in this work is the problem of acoustic propagation in guides lined with locally or non locally reacting materials with the presence of mean fluid flow. In several industrial systems such as aircraft jet engines, mufflers exhaust and ventilation systems, noise is mostly channeled outside by guides of more or less complex geometries. A study of waveguides makes it possible to predict and understand the physical phenomena such as refraction, convection, absorption and wave attenuation. In waveguides studies, guides are often considered infinitely long to get rid of some phenomena (reflection for example) at their ends. Solving the problem of acoustic propagation in infinite guides…
Structural characterization of 2,2-di-n-butyl-4-methyl-1,3,2-dioxastannolane isolated from supercritical CO2 conditions
2009
The title compound has been isolated as single crystals from the synthesis of propylene carbonate from racemic 1,2-propanediol and carbon dioxide using n-Bu2SnO as a catalyst precursor. The X-ray crystallographic structure analysis revealed the self-assembly of di-n-butyltin(IV) 1,2-propanediolate units, linked together through long-distance Sn-O interactions leading to a one-dimensional polymeric architecture organized in a syndiotactic arrangement. The coordination geometry around the tin atoms can be described as an unusual faced-capped trigonal bipyramidal environment.
A comparative high-pressure jet-stirred reactor study on the oxidation of pentanol isomers: 1-, 2- and 3- pentanol
2018
International audience
An experimental and modelling study of the oxidation of 3-pentanol at high pressure
2018
International audience; High pressure oxidation of 3-pentanol is investigated in a jet-stirred reactor and in a shock tube. Experiments in the reactor were carried out at 10 atm, between 730 and 1180 K, for equivalence ratios of 0.35, 0.5, 1, 2, 4 and 1000 ppm fuel, at a constant residence time of 0.7 s. Reactant, product and intermediate species mole fractions were recorded using Fourier transform infrared spectroscopy (FTIR) and gas chromatography (GC). Ignition delay times were measured for 3-pentanol/O2 mixtures in argon in a shock tube at 20 and 40 bar, in a temperature range of 1000–1470 K and for equivalence ratios of 0.5, 1 and 2. The fuel did not show any low-temperature reactivity…
Possibilities of surface reaction coupling with transport phenomena
1977
International audience; The thermodynamic approach of nonequilibrium phenomena allows, through the construction of entropy production, appropriate fluxes generalized forces to be identified, and the possibility of coupling to be detected. For the interface phase the expression entropy production consists of two parts: one for irreversible phenomena in the surface (chemical reactions and transport); and the second for transport processes between volumic phases due to the discontinuity of intensive surface parameters. Accordingly in the linear range, the phenomenological relations establishing the thermodynamic coupling between fluxes and forces of the same tensorial order may cause couplings…
CFD simulations
2022
Intermittency in the homopolar dynamo
2005
URL: http://www-spht.cea.fr/articles/s05/152 Rigas Jurmala, Rigas Jurmala, Latvia, June 27 - July 1st, 2005; We study a modified Bullard dynamo and show that this system is equivalent to a nonlinear oscillator subject to a multiplicative noise. The stability analysis of this oscillator is performed. Two bifurcations are identified, first towards an ``intermittent'' state where the absorbing (non-dynamo) state is no more stable but the most probable value of the amplitude of the oscillator is still zero and secondly towards a ``turbulent'' (dynamo) state where it is possible to define unambiguously a (non-zero) most probable value around which the amplitude of the oscillator fluctuates. The …
Isotope Shifts of Radium Monofluoride Molecules
2021
Isotope shifts of $^{223-226,228}$Ra$^{19}$F were measured for different vibrational levels in the electronic transition $A^{2}{}{\Pi}_{1/2}\leftarrow X^{2}{}{\Sigma}^{+}$. The observed isotope shifts demonstrate the particularly high sensitivity of radium monofluoride to nuclear size effects, offering a stringent test of models describing the electronic density within the radium nucleus. Ab initio quantum chemical calculations are in excellent agreement with experimental observations. These results highlight some of the unique opportunities that short-lived molecules could offer in nuclear structure and in fundamental symmetry studies.
Collective excitations of 3He clusters
1991
Collective excitations of3He clusters are studied by treating the cluster as a quantum liquid drop. We have used the Random-Phase Approximation sum rules technique within a Density Functional Formalism. Results forL=2 to 10 surface modes and theL=0 volume mode are presented.