Méthode de Relaxation Dynamique incrémentale

National audienceSee http://hal.archives-ouvertes.fr/docs/00/59/29/46/ANNEX/r_ZL662YL9.pd

Numerical study of dynamic relaxation with kinetic damping applied to inflatable fabric structures with extensions for 3D solid element and non-linear behavior

International audienceThis work mainly deals with the numerical study of inflatable fabric structures. As implicit integration schemes can lead to numerical difficulties such as singular stiffness matrices, explicit schemes are preferred. Since the final objective of this study is to obtain the final shape of a structure, a dynamic relaxation (DR) method is used. These methods allow us to obtain the final and stable shape of the inflatable fabric structures without doing so many time increments, which is the case when using a classical explicit integration method. Han and Lee [5] proposed an extension of the DR method stated by Barnes [13] suitable for triangular elements and elastic behavior. There are two main contributions in this paper. Firstly, we propose a modification of Han and Lee's method, allowing it to be used with any kind of membrane or solid finite elements and any reversible behavior. Secondly, we propose to rewrite the expression initially introduced by Barnes. Furthermore, these proposals are adapted for incremental loadings, allowing this way to obtain the pseudo-equilibriums of the intermediate phases. Numerical examples from academic problems (rectangular and circular membranes) show the efficiency and the reliability of proposed methods, with linear elasticity behavior, and also with a non-linear incremental behavior and finite deformation states

Experimental and Numerical Study of High-Altitude Ignition of a Turbojet Combustor

This paper aims at contributing to the methodology used for the numerical prediction of ignition inside a combustion chamber. For this purpose, experiments are carried out in a model combustor with improved optical access. Laser tomography and high-speed video give a first insight of the unsteady airflow and the flame structure. Laser Doppler Anemometry is used to measure the gas flow velocity field, and the non-reactive two-phase flow is studied in detail using Particle Doppler Analysis. The velocity field of the burning spray is measured using Particle Image Velocimetry. Ignition tests are performed to evaluate the minimum global equivalence ratio. This in-depth database is used to validate RANS simulations conducted in parallel using ONERA CFD code CEDRE. The numerical model for transient, spherical kernel ignition, proposed in previous work, has been improved and fully implemented in CEDRE. A first parametric study on a basic configuration has been partially validated for gaseous, monodisperse and polydisperse two-phase mixtures, and gives a better understanding of the first stages of flame propagation. This model is then used in combination with CEDRE to estimate the ignition probability of given spark- plug positions in the model combustor

Міхал Бобжинський: суспільно-політична діяльність

Розглянута суспільно-політична діяльність визначного представника краківської історичної школи М. Бобжинського. Акцентовано увагу на зв’язку наукових поглядів історика з його політичною практикою. Охарактеризовано дискусії, які досьогодні точаться серед науковців щодо оцінки результатів його діяльності.Рассмотрена общественно-политическая деятельность выдающегося представителя краковской исторической школы М. Бобжинского. Акцентировано внимание на связи научных взглядов историка с его политической практикой. Охарактеризованы дискуссии, которые досегодня ведутся среди ученых относительно оценки результатов его деятельности.The socio-political activities of M. Bobzhynski – a prominent representative of the Krakow historical school – are reviewed. Attention is given to the connection of the historian scholarly views with his political practice. The discussions that until now are going on among scholars in evaluating the results of his work are characterised

Evaluating the pronunciation of proper names by four French grapheme-to-phoneme converters

International Speech Communication Association (Isca) - International Astronautical Federation.ISBN : 13 9781604234480.This article reports on the results of a cooperative evaluation of grapheme-to-phoneme (GP) conversion for proper names in French. This work was carried out within the framework of a general evaluation campaign of various speech and language processing devices, including text-to-speech synthesis. The corpus and the methodology are described. The results of 4 systems are analysed: with 12-20% word error rates on a list of 8,000 proper names, they give a fairly accurate picture of the progress achieved, the state-of-the-art and the problems still to be solved, in the domain of GP conversion in French. In addition, the resources and collected data will be made available to the scientific and industrial community, in order to be re-used in future bench-marks

Experimental Analysis of the Global Performance and the Flow Through a High-Bypass Turbofan in Windmilling Conditions

A detailed study of the air flow through the fan stage of a high-bypass, geared turbofan in windmilling conditions is proposed, to address the key performance issues of this severe case of off-design operation. Experiments are conducted in the turbofan test rig of ISAE, specifically suited to reproduce windmilling operation in an ambient ground setup. The engine is equipped with conventional measurements and radial profiles of flow quantities are measured using directional five-hole probes to characterize the flow across the fan stage and derive windmilling performance parameters. These results bring experimental evidence of the findings of the literature that both the fan rotor and stator operate under severe off-design angle-of-attack, leading to flow separation and stagnation pressure loss. The fan rotor operates in a mixed fashion: spanwise, the inner sections of the rotor blades add work to the flow while the outer sections extract work and generate a pressure loss. The overall work is negative, revealing the resistive loads on the fan, caused by the bearing friction and work exchange in the different components of the fan shaft. The parametric study shows that the fan rotational speed is proportional to the mass flow rate, but the fan rotor inlet and outlet relative flow angles, as well as the fan load profile, remain constant, for different values of mass flow rate. Estimations of engine bypass ratio have been done, yielding values higher than six times the design value. The comprehensive database that was built will allow the validation of 3D Reynolds-averaged Navier–Stokes (RANS) simulations to provide a better understanding of the internal losses in windmilling conditions

Response surface methodology to optimise Accelerated Solvent Extraction of steviol glycosides from Stevia rebaudiana Bertoni leaves

Following the approval of steviol glycosides as a food additive in Europe in December 2011, large-scale stevia cultivation will have to be developed within the EU. Thus there is a need to increase the efficiency of stevia evaluation through germplasm enhancement and agronomic improvement programs. To address the need for faster and reproducible sample throughput, conditions for automated extraction of dried stevia leaves using Accelerated Solvent Extraction were optimised. A response surface methodology was used to investigate the influence of three factors: extraction temperature, static time and cycle number on the stevioside and rebaudioside A extraction yields. The model showed that all the factors had an individual influence on the yield. Optimum extraction conditions were set at 100°C, 4min and 1 cycle, which yielded 91.8%±3.4% of total extractable steviol glycosides analysed. An additional optimisation was achieved by reducing the grind size of the leaves giving a final yield of 100.8%±3.3%