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Articles de revues sur le sujet "Laser-Doppler Anemometrie (LDA)"
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Glaremin, Lukas, Yannick Dück et Christian Jokiel. « Optimierung eines Verfahrens zur Entsedimentation von Stauräumen und Reduktion von Methanemissionen mittels Laser-Doppler-Anemometrie (LDA) ». WASSERWIRTSCHAFT 110, no 6 (juin 2020) : 29–35. http://dx.doi.org/10.1007/s35147-020-0396-9.
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Ristic, Slavica, Mirjana Puharic, Marina Kutin et Dusan Matic. « Determination of air and hydrofoil pressure coefficient by laser doppler anemometry ». Theoretical and Applied Mechanics 37, no 1 (2010) : 17–35. http://dx.doi.org/10.2298/tam1001017r.
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Some results of experiments performed in water cavitation tunnel are presented. Pressure coefficient (Cp) was experimentally determined by Laser Doppler Anemometry (LDA) measurements. Two models were tested: model of airplane G4 (Super Galeb) and hydrofoil of high speed axial pump. These models are not prepared for conventional pressure measurements, so that LDA is applied for Cp determination. Numerical results were obtained using a code for average Navier-Stokes equations solutions. Comparisons between computational and experimental results prove the effectiveness of the LDA. The advantages and disadvantages of LDA application are discussed. Flow visualization was made by air bubbles.
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Ramaprian, B. R., et M. S. Chandrasekhara. « LDA Measurements in Plane Turbulent Jets ». Journal of Fluids Engineering 107, no 2 (1 juin 1985) : 264–71. http://dx.doi.org/10.1115/1.3242472.
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Measurements on the mean and most of the significant turbulent properties of plane isothermal and heated (but essentially “nonbouyant”) jets are reported. The velocity measurements were made using two-component, frequency-shifted Laser Doppler Anemometry (LDA) and the temperature measurements were made using fast-response resistance thermometry. A simple but effective technique was developed for obtaining accurate velocity measurements from the LDA in a nonisothermal environment. These measurements, some of which are the first of their kind, provide an independent data base with which to compare existing hot-wire data on jets. The LDA measurements indicate lower turbulence intensities and lower turbulent fluxes compared to the hot-wire data.
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Kadambi, J. R., S. J. Schneider et W. A. Stewart. « Laser Anemometry Measurements of Natural Circulation Flow in a Scale Model PWR System ». Journal of Engineering for Gas Turbines and Power 112, no 2 (1 avril 1990) : 261–66. http://dx.doi.org/10.1115/1.2906172.
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Experimental studies were conducted to investigate the natural circulation of a singlephase fluid in a scale model pressurized water reactor system during a postulated degraded core accident. A half-section of a 1/7 scale model with a plexiglass adiabatic window was used. Water and sulfurhexafluoride (SF6) were used as the fluid. Laser-Doppler anemometry (LDA) was used in making the velocity measurements along the center plane of the model at five elevations.
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Apiputikul, Chatchalong, Kheamrutai Thamaphat, Monrudee Ranusawad et Pichet Limsuwan. « Uncomplicated Setting Apparatus for Measurement of Fluid Flow Rate Using Laser Doppler Technique : Physics Teaching ». Advanced Materials Research 770 (septembre 2013) : 366–69. http://dx.doi.org/10.4028/www.scientific.net/amr.770.366.
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Laser Doppler velocimetry (LDV) or laser Doppler anemometry (LDA) is the technique of using the Doppler shift in a laser beam to determine the fluid velocity. In this work, dual beam mode (two incident beams, single observation location) was selected to use. A cost effective and easy module for measurement of water flow rate was designed and constructed. A He-Ne laser with a wavelength of 632.8 nm was used as a light source. The laser was passed through a beam splitter and divided into two beams with identical intensity and coherence. Subsequently, the two laser beams travelled to a focusing lens with a focal length of 100 mm and focused on a center of water flow channel in quartz cuvette with a dimension of 1 × 1 × 5 cm3. The beam angle was set at 4.96°. When the seeding particles, bubbles and microorganism in water, were moving through the intersection point of two beams, the light was scattered. The scattered light was collected by photodetector connected to processing system. The frequency of scatterred light is shifted according to the Doppler shift relations due to effect of Rayleigh scattering. The water flow rate can be calculated from Doppler shift frequency.
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Kysela, Bohuš, Jiří Konfršt, Ivan Fořt et Zdeněk Chára. « CFD Simulation of the Discharge Flow from Standard Rushton Impeller ». International Journal of Chemical Engineering 2014 (2014) : 1–7. http://dx.doi.org/10.1155/2014/706149.
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The radial discharge jet from the standard Rushton turbine was investigated by the CFD calculations and compared with results from the Laser Doppler Anemometry (LDA) measurements. The Large Eddy Simulation (LES) approach was employed with Sliding Mesh (SM) model of the impeller motion. The obtained velocity profiles of the mean ensemble-averaged velocity and r.m.s. values of the fluctuating velocity were compared in several distances from the impeller blades. The calculated values of mean ensemble-averaged velocities are rather in good agreement with the measured ones as well as the derived power number from calculations. However, the values of fluctuating velocities are obviously lower from LES calculations than from LDA measurements.
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Sierens, R., et P. Snauwaert. « Study of the Flow Pattern in Compact Manifold Type Junctions by LDA ». Journal of Engineering for Gas Turbines and Power 109, no 4 (1 octobre 1987) : 452–58. http://dx.doi.org/10.1115/1.3240063.
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In this paper pressure and velocity measurements on two theoretical compact manifold type junctions (compact pulse converters) under steady-state conditions are described. The velocity measurements are done with Laser-Doppler anemometry (LDA). The pressure distributions and the velocity profiles for different flow configurations and different mass flow rates are presented. These results are used for calculation of loss coefficients and for comparison with a numerical algorithm for simulating the three dimensional turbulent quasi-steady flow in compact manifold type junctions.
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Arcoumanis, C., J. H. Whitelaw et P. Flamang. « Flow in the Inlet Manifold of a Production Diesel Engine ». Proceedings of the Institution of Mechanical Engineers, Part C : Mechanical Engineering Science 203, no 1 (janvier 1989) : 39–49. http://dx.doi.org/10.1243/pime_proc_1989_203_084_02.
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The flow in the inlet manifold of a Ford direct injection diesel engine has been characterized by laser Doppler anemometry under motored conditions at engine speeds between 300 and 1100 r/min. Plexiglass windows have been inserted at three locations in adjacent manifold branches of the four-cylinder engine and back-scatter LDA was used to provide information about the ensemble-averaged and in-cycle axial and radial velocities at various spatial locations within the inlet channels during the engine cycle.
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Delgadillo, J. A., Kayed Al, D. Vo et A. S. Ramamurthy. « CFD simulations of a hydrocyclone in absence of an air core ». Journal of Mining and Metallurgy, Section B : Metallurgy 48, no 2 (2012) : 197–206. http://dx.doi.org/10.2298/jmmb111123028d.
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Computational Fluid Dynamics (CFD) is a versatile means to predict the characteristics of flow in fluid mechanics problems under a wide range of design and operating conditions . Applying the CFD in many engineering fields alleviates the problem of the usual engineering design. Recent advance in computational methods and computer technology make CFD an efficient means to study the dynamics of many physical systems. CFD simulations use three dimensional grid and the Reynolds Stress Model (RSM) to investigate the flow without air core in a 6? hydrocyclone have been conducted using FLUENT. The numerical results are compared with the experimental data related to the Laser Doppler Anemometry (LDA) measurements of velocity. In the experimental study, a new procedure is developed to reorient the laser beams that permit one to measure two velocity components at a single point using LDA. The conclusion developed from these experiments enables one to use the LDA directly in the hydrocyclone wall without recourse to auxiliary attachments such as an enclosing box that usually used to minimize the refraction effects of laser beams which are caused by the curved solid wall of the hydrocyclone and the refractive index of the test medium.
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Okulov, Valery L., Igor V. Naumov, Robert F. Mikkelsen, Ivan K. Kabardin et Jens N. Sørensen. « A regular Strouhal number for large-scale instability in the far wake of a rotor ». Journal of Fluid Mechanics 747 (17 avril 2014) : 369–80. http://dx.doi.org/10.1017/jfm.2014.174.
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AbstractThe flow behind a model of a wind turbine rotor is investigated experimentally in a water flume using particle image velocimetry (PIV) and laser Doppler anemometry (LDA). The study performed involves a three-bladed wind turbine rotor designed using the optimization technique of Glauert (Aerodynamic Theory, vol. IV, 1935, pp. 169–360). The wake properties are studied for different tip speed ratios and free stream speeds. The data for the various rotor regimes show the existence of a regular Strouhal number associated with the development of an instability in the far wake of the rotor. From visualizations and a reconstruction of the flow field using LDA and PIV measurements it is found that the wake dynamics is associated with a precession (rotation) of the helical vortex core.
Thèses sur le sujet "Laser-Doppler Anemometrie (LDA)"
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Zaremba, Matouš. « Vliv provozních parametrů na kvalitu rozprašování kapalin u dvou-médiových trysek ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230587.
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This master’s thesis deals with measurement of spray characteristics of Effervescent atomizers intended for burning waste and heavy fuels. Atomizers were tested on cold test bench by means of Phase Doppler Anemometry. Spray characteristics were evaluated for many different regimes of pressure, temperature and Gas to liquid ratio. The aim of this measurement is to compare flow regimes and their influence on the quality of spray characteristics. The theoretical part describes basic fundamental principles of liquid atomization, effervescent atomization and principles of laser diagnostic methods. The practical part is engaged with improvements in test bench and setting up and optimization of the laser measuring system. Results contain visualization of spray, velocity profiles and drop size distribution in various operating flow regimes of the jet.
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Allen, John Thomas. « Laser-based measurements of two-phase flashing propane jets ». Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298973.
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Swales, Christopher. « Advance LDA techniques for measurement of 3D boundary layer velocity profiles on a helicopter rotor ». Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327721.
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Ringleb, Ansgar. « Numerische und experimentelle Untersuchung der fluiddynamischen Eigenschaften von Strahlströmungen in begrenzten Räumen ». Universitätsverlag der Technischen Universität Chemnitz, 2017. https://monarch.qucosa.de/id/qucosa%3A20850.
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In der vorliegenden Arbeit wurden Strömungen räumlich begrenzter Strahlen untersucht. Zum einen wurde die Ausströmung eines runden Strahls in ein Rohr betrachtet, der sog. begrenzte Strahl. Zum anderen wurde die Ausströmung von 7 hexagonal angeordneten runden Strahlen in ein Rohr betrachtet, das sog. hexagonale Strahlbündel. Die Motivation zur vorliegenden Arbeit ergab sich aus der Entwicklung von Durchflussmessgeräten, die als Bypassapparaturen ausgeführt sind und stromabwärts des Staudruckkörpers ein Strömungsgebiet mit begrenzten Strahlen aufweisen. Dafür wurden mit Hilfe der Ähnlichkeitstheorie die zugrundeliegenden Kennzahlen bestimmt. Besonderes Augenmerk lag auf der Charakterisierung der instationären bzw. turbulenten Strömungseigenschaften für Reynolds-Zahlen zwischen 1.000 und 20.000. Es wurden die selbstähnlichen Eigenschaften der Strömungen untersucht, wobei sich insbesondere für den begrenzten Strahl wichtige Erkenntnisse ergaben. Für das hexagonale Strahlbündel wurden mit Hilfe der numerischen Strömungssimulation die grundlegenden Eigenschaften des Strömungsfeldes untersucht. Dabei weisen die Geometriekennzahlen einen dominierenden Einfluss auf. So konnten in Abhängigkeit zum Durchmesserverhältnis und Strahlabstand drei Strömungsformen identifiziert und experimentell mittels Laser-Doppler Anemometrie nachgewiesen werden. Eine wesentliche Fragestellung bestand in der Anwendung der numerischen Strömungssimulation, des RANS-Ansatzes und des SST-Turbulenzmodells. Dazu wurde die Anpassung der Modellkoeffizienten untersucht, wobei für den begrenzten Strahl ein allgemein gültiger Satz gefunden wurde.In the present work flows of spatially limited radiation were investigated. On the one hand, the outflow of a round jet into a pipe was considered, the so-called confined jet. On the other hand, the outflow of 7 hexagonal arranged round jets into a pipe was con-sidered, the so-called hexagonal jet array. The motivation for the present work arose from the development of flowmeters which are designed as bypass apparatures that have a jet array flow downstream of the dynamic pressure body. For this purpose the underlying similarity parameters were determined. Special attention was paid to the cha-racterization of transient and turbulent flow properties for Reynolds numbers between 1,000 and 20,000. The self-similar properties of the flows were investigated with im-portant findings in particular for the confined jet. For the hexagonal jet array the basic properties of the flow field were investigated by using computational fluid dynamics. The geometric similarity parameters have a dominant influence. Thus, depending on the di-ameter ratio and jet distance ratio, three flow patterns could be identified and experimen-tally detected by the use of laser Doppler anemometry. An important question was the application of the computational fluid dynamic method, the RANS approach and the SST turbulence model. For this purpose a generally valid set of model coefficients was found for the confined jet flow.
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García, Vizcaino David. « Sistema láser de medida de velocidad por efecto doppler de bajo coste para aplicaciones industriales e hidrodinámicas ». Doctoral thesis, Universitat Politècnica de Catalunya, 2005. http://hdl.handle.net/10803/6892.
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La utilización práctica del efecto Doppler en la emisión láser fue propuesta desde los inicios del desarrollo de los láseres en los años sesenta. Sólo en los años ochenta la investigación realizada pudo salir del laboratorio y dar lugar a la fabricación de aparatos de medida de velocidad comerciales. A partir de los noventa estos aparatos se popularizaron rápidamente. Actualmente se utilizan medidores de velocidad láser por efecto Doppler en múltiples aplicaciones, entre las que sobresale la medida de velocidad de fluidos, para estudios aéreo e hidrodinámicos. Sus características únicas, como la precisión obtenida en la medida, su alta resolución espacial y el carácter no intrusivo, sólo han comenzado recientemente a tener rivales de consideración, como pueden ser la velocimetría de imagen de partículas (PIV). También la medida de velocidades de móviles sólidos comienza a resultar, con el abaratamiento general de los componentes opto-electrónicos, un objetivo para muchas empresas. Entre las aplicaciones de este tipo se contemplan el control de velocidad de los vehículos en carretera y el control de procesos industriales del ramo textil, papelero y deempresas fabricantes de cables, entre otros.
Empresas europeas y americanas, como Dantec Electronik y TSI, por citar las más representativas, comercializan aparatos LDA de propósito general de altas prestaciones. Hasta la fecha estos sistemas sólo podían ser adquiridos por importantes centros de investigación o grandes empresas, debido a su elevado coste. El futuro comercial de la velocimetría láser Doppler exige la fabricación de aparatos más económicos y adaptados a las necesidades del cliente. Muchos de los sistemas actuales son voluminosos,
difíciles de manejar y con potencias de trabajo elevadas. Se está llevando a cabo un importante trabajo para conseguir reducir el tamaño y coste de los equipos sin perder sus principales prestaciones. Asimismo la alta velocidad y capacidad de cálculo de los ordenadores personales actuales debe hacer innecesaria la inclusión de procesadores específicos para estos equipos.
Presentamos el diseño y construcción de un sistema integral de medida de dos componentes de la velocidad, sistema 2D-LDA, para aplicaciones industriales e hidrodinámicas de baja potencia.
Siguiendo la filosofía delineada arriba, el diseño de nuestro sistema LDA fue realizado utilizando únicamente una fuente laser y un módulo detector. Los sistemas LDA de medida de dos componentes de velocidad comercialmente disponibles, por el contrario, emplean dos longitudes de onda óptica y dos fotodetectores independientes. Las emisiones azul y verde típicas de los láseres de ion-Ar son las longitudes de onda a menudo elegidas en este tipo de medidas.
Por otra parte, se ha empleado los dos canales de entrada de una tarjeta de adquisición de uso general para realizar el disparo multinivel. Esta configuración permite trabajar en cada momento con la parte de señal burst teóricamente más adecuada, con mayor valor de relación señal a ruido.
Este trabajo ha sido financiado por la CICYT Proyecto PETRI 95-0249-OP:
REALIZACIÓN DE SISTEMAS LÁSER PORTÁTILES DE MEDIDA DE VELOCIDAD POR EFECTO DOPPLER (LDA-LDV) DE BAJO COSTE PARA APLICACIONES INDUSTRIALES E HIDRODINÁMICAS.
The practical use of the Doppler effect at optical wavelengths was proposed at the early beginning of the development of the laser, in the sixties. However, it was only in the eighties when the results of the experimental work could finally get out of the laboratories, and the first Laser Velocimeters were commercially available. In the nineties this kind of systems became rapidly popular. Nowadays the Laser Velocimeters based on the Doppler frequency shift find a lot of important applications, especially in some industrial processes and in hydrodynamic and aerodynamic research.
The unique characteristics of the Laser Doppler Velocimetry (LDV) only recently have encountered a rival technique in the Particle Image Velocimetry (PIV), for applications on fluids. The main features of LDV systems are the accuracy and the speed of the measurements, the high spatial resolution and, of course, the non-intrusive character of the technique. Moreover this kind of systems present advantages not only in fluid applications: actually it can compete with the microwave radar in the estimation of the velocity of solid targets. This becomes possible due to the
progressive reduction of prices of optoelectronic devices and the improvement of its performances. The monitoring of the traffic velocity and the control of machinery in the manufacture of paper, wires and cables or thread can be mentioned among these applications.
European an American companies, as Dantek Electronic or TSI, to mention the two most representative, commercialize high performance general-purpose LDV systems. Up to the date these instruments are sizeable and expensive, and its use requires some special training. There is not doubt that the future market of the LDV systems goes through a substantial decrease of prices and, indeed, through the possibility of custom-built designs. The potential number of users would increase then in an important manner. Many efforts are now being devoted by researchers in that direction. Moreover, the important improvement of capabilities of the desktop computers makes unnecessary the special electronic processors that, up to now, have been provided by the manufacturers of LDV systems as a part of them.
In this Thesis the design and realization of a complete Laser Doppler Anemometer is presented. The system can measure two components of a fluid velocity (2D-LDA) and originally it was conceived to be used in industrial and hydrodynamics applications.
Following the philosophy outlined above, the design of our LDA system was performed with only one laser source and one detector module. The common commercially available LDAs, on the contrary, designed to measure two components of velocity, use two different optical wavelengths and two independent photodiodes.
On the other hand, a general-purpose acquisition card with two input channels has been used to implement a multilevel trigger. The configuration performed here permits to work in each moment with the part of the burst having the best signal to noise ratio.
This work has been supported by the Spanish Government, CICYT project PETRI 95-0249-OP.
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Derlaga, Joseph Michael. « An Experimental Study of Longitudinally Embedded Vortices in a Turbulent Boundary Layer via the Non-Invasive Comprehensive LDV Technique ». Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32776.
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This report documents the measurements of turbulence quantities resulting from vortices embedded in a zero pressure gradient turbulent boundary layer. Turbulent boundary layers are found in most flow regimes over large scale vehicles and have been studied for many years. Various systems to control separation of boundary layers have been proposed, but vortex generators have proven to be an economical choice as they are often used to fix deficiencies in a flow field after large scale production of a vehicle has commenced. In order to better understand the interaction between vortex generators and the boundary layer in which they are embedded, an experiment has been performed using through non-invasive Comprehensive Laser Doppler Velocimeter.
The results show that normalization on edge velocity is appropriate for comparison with previous work. The 1/S parameter and vq^2 parameter were found to be most appropriate to correlate the Reynolds stresses and triple products, respectively. The higher inflow edge velocity and greater momentum thickness, creating a lower vortex generator to boundary layer height ratio, result in a more diffuse vortex as compared to previous work conducted in the same wind tunnel, with the same geometry, but with different inflow conditions.Master of Science
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Kuhl, David Derieg. « Near Wall Investigation of Three Dimensional Turbulent Boundary Layers ». Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34676.
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This report documents the experimental study for four different three-dimensional turbulent flows. The investigation focuses on near wall measurements in these flows. Several experimental techniques are used in the studies; however, the bulk of the investigation focuses on a three-orthogonal-velocity-component fiber-optic laser Doppler anemometer (3D-LDA) system. The control volume of the 3D-LDA is on the order of 50 micro-meter in size, or a y+ distance of around 2.3 units (using average values of Uτ and ν from the experiment). An auxiliary small boundary layer wind tunnel (auxiliary tunnel) and a low speed linear compressor cascade wind tunnel (cascade tunnel) are utilized in this study. One of four flow experiments is done in the auxiliary tunnel the other three are in the cascade tunnel. The first three-dimensional turbulent flow is a vortical flow created by two half-delta wing vortex generators. Near wall secondary flow features are found. The second flow is an investigation of the first quarter chord tip gap flow in the cascade tunnel. Strong three-dimensional phenomena are found. The third flow investigated is the inflow to the compressor cascade with the moving wall. The experiment records shear layer interaction between the upstream flow and moving wall. Finally the fourth flow investigated is the inflow to the compressor cascade with the moving wall with half-delta wing vortex generators attached. Phase-averaged data reveal asymmetrical vortex structures just downstream of the vortex generators. This is the first time any near wall data has been taken on any of these flows.Master of Science
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Beauquel, Julien A. « Numerical investigation on the in-cylinder flow with SI and CAI valve timings ». Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/21548.
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The principle of controlled auto-ignition (CAI) is to mix fuel and air homogeneously before compressing the mixture to the point of auto-ignition. As ignition occurs simultaneously, CAI engines operate with lean mixtures preventing high cylinder pressures. CAI engines produce small amounts of nitrogen oxides (NOx) due to low combustion temperatures while maintaining high compression ratios and engine efficiencies. Due to simultaneous combustion and lean mixtures, CAI engines are restricted between low and mid load operations. Various strategies have been studied to improve the load limit of CAI engines. The scope of the project is to investigate the consequences of varying valve timing, as a method to control the mixture temperature within the combustion chamber and therefore, controlling the mixture auto-ignition point. This study presents computational fluid dynamics (CFD) modelling results of transient flow, inside a 0.45 litre Lotus single cylinder engine. After a validation process, a chemical kinetics model is combined with the CFD code, in order to study in-cylinder temperatures, the mixture distribution during compression and to predict the auto-ignition timing. The first part of the study focuses on validating the calculated in-cylinder velocities. A mesh sensitivity study is performed as well as a comparison of different turbulence models. A method to reduce computational time of the calculations is presented. The effects of engine speed on charge delay and charge amount inside the cylinder, the development of the in-cylinder flow field and the variation of turbulence parameters during the intake and compression stroke, are studied. The second part of the study focuses on the gasoline mixture and the variation of the valve timing, to retain different ratios of residual gases within the cylinder. After validation of the model, a final set of CFD calculations is performed, to investigate the effects of valve timing on flow and the engine parameters. The results are then compared to a fully homogeneous mixture model to study the benefits of varying valve duration. New key findings and contributions to CAI knowledge were found in this investigation. Reducing the intake and exhaust valve durations created a mixture temperature stratification and a fuel concentration distribution, prior to auto-ignition. It resulted in extending the heat release rate duration, improving combustion. However, shorter valve timing durations also showed an increase in heat transfer, pumping work and friction power, with a decrease of cylinder indicated efficiency. Valve timing, as a method to control auto-ignition, should only be used when the load limit of CAI engines, is to be improved.
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Andersson, Harald. « Numerical and experimental study of confluent jets supply device with variable airflow ». Licentiate thesis, Högskolan i Gävle, Energisystem och byggnadsteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-29271.
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In recent years, application of confluent jets for design of ventilation supply devices has been studied. Similarly, numerus studies have been made on the potential and application of variable air volume (VAV) in order to reduce the energy demand of ventilation systems. This study investigates the combination of supply devices based on confluent jets and VAV, both in terms of the nearfield flow behavior of the device and the impact on thermal comfort, indoor air quality and energy efficiency on a classroom-level space when the airflow rate is varied. The method used in this study is an experimental field study where the confluent jets-based supply devices were compared to the previously installed displacement ventilation. The field study evaluated the energy efficiency, thermal comfort and indoor air quality of the two systems. In the case of the confluent jets supply devices, airflow rate was varied in order to see what impact the variation had on the performance of the system for each airflow rate. Furthermore, the confluent jets supply devices were investigated both experimentally and numerically in a well insulated test room to get high resolution data on the particular flow characteristics for this type of supply device when the airflow rate is varied. The results from the field study show nearly uniform distribution of the local mean age of air in the occupied zone, even in the cases of relatively low airflow rates. The airflow rates have no significant effect on the degree of mixing. The thermal comfort in the classroom was increased when the airflow rate was adapted to the heat load compared to the displacement system. The results lead to the conclusion that the combination of supply devices based on confluent jets can reduce energy usage in the school while maintaining indoor air quality and increasing the thermal comfort in the occupied zone. The results from the experimental and numerical study show that the flow pattern and velocity in each nozzle is directly dependent on the total airflow rate. However, the flow pattern does not vary between the three different airflow rates. The numerical investigation shows that velocity profiles for each nozzle have the same pattern regardless of the airflow rate, but the magnitude of the velocity profile increases as the airflow increases. Thus, a supply device of this kind could be used for variable air volume and produce confluent jets for different airflow rates. The results from both studies show that the airflow rate does not affect the distribution of the airflow on both near-field and room level. The distribution of air is nearly uniform in the case of the near-field results and the room-level measurement shows a completely uniform degree of mixing and air quality in the occupied zone for each airflow rate. This means that there is potential for combining these two schemes for designing air distribution systems with high energy efficiency and high thermal comfort and indoor air quality.Under senare tid har applikation av Confluent jets för design av tilluftsdon studerats. Många studier har även utförts över potentialen av att applicera variabelt luftflöde (VAV) för att minska energianvändningen i ventilationssystem. Denna studie undersöker möjligheten att kombinera Confluent jets-don med VAV, både med avseende på den lokala flödesbilden och dess påverkan på termisk komfort, luftkvalitet och energieffektivitet i en klassrumsmiljö där luftflödes varieras. Denna studie baseras dels på en experimentell fältstudie där tilluftsdon baserade på Confluents jets jämfördes med befintliga deplacerande tilluftsdon. Fältstudien utvärderade energieffektiviteten, den termiska komforten och luftkvaliteten för båda typerna av tillluftsdon. Confluent jets-donen testades under varierat luftflöde för att se påverkan av flödesvariationen på ventilationens prestation under de olika flödena. Utöver fältstudien testades Confluent jets-donen experimentellt och numeriskt i ett välisolerat test-rum för få den detaljerade flödeskarakteristiken för den här typen tilluftsdon vid varierat luftflöde. Resultaten från fältstudien visar på en jämn fördelning av den lokala luftsmedelåldern i vistelsezonen, även för fallen med relativt låga luftflöden. Luftflöden har ingen signifikant effekt på omblandningen. Den termiska komforten i klassrummet ökade när luftflödet anpassades efter värmelasten jämfört med de deplacerande donen. Slutsatsen från fältstudien är att kombinationen av VAV och Confluent jets-don kan användas för att minska energianvändningen på skolan och bevara luftkvaliteten och den termiska komforten i vistelsezonen. Resultaten från den experimental och numeriska studien visar luftflödet och lufthastigheten i varje enskild dysa är direkt beroende på det totala luftflödet genom donet. Dock är flödesfördelningen mellan dysorna oberoende av de tre olika luftflödena. Den numeriska undersökningen visar att flödesprofilen för varje dysa är konstant trots att flödet varieras, men amplituden för varje profil ökar med en höjning av luftflödet. Det betyder att tilluftsdon av den här typen kan användas med VAV för att producera Confluent jets för olika luftflöden. Resultaten från båda studierna visar att luftflöde inte påverkar fördelningen av luften vare sig längs luftdonen eller på rumsnivå. Fördelningen av luften är nästan helt jämn längs donen och på rumsnivå är omblandningen och luftkvalitet den samma för varje luftflöde. Det betyder att det finns potential för att kombinera det här två teknikerna för att designa luftdistribueringssystem med hög energieffektivitet och hög termisk komfort med god luftkvalitet.
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Diop, Moussa. « Transition à la turbulence en écoulements compressibles décollés ». Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0473/document.
Texte intégralRésumé :
Les recherches sur les instationnarités des Interactions Ondes de Choc Couches Limites (IOCCL) turbulentes ont permis une description détaillée de celles-ci tant expérimentalement que numériquement . Ceci a conduit à plusieurs schémas susceptibles d'expliquer les respirations à basses fréquences observées dans de tels écoulements. Les configurations avec des conditions amont laminaires ou transitionnelles ont été moins étudiées.Dans le cadre du programme Européen TFAST, un important effort a été mené afin de développer des dispositifs expérimentaux, conjointement à des simulations numériques, permettant une étude détaillée de ces configurations. Dans le cadre de cette thèse, on a mis en place une configuration de réflexion d'onde de choc sur une couche limite laminaire pour un nombre de Mach de 1.68. L'utilisation des métrologies classiques (Anémométrie Laser Doppler, Anémométrie Fil Chaud), adaptées à ces conditions expérimentales particulières, a permis de décrire les propriétés spatio-temporelles de ces écoulements. Le champ moyen a été caractérisé et comparé aux théories classique et aux résultats obtenus dans différentes souffleries.Un schéma décrivant le mécanisme de transition à la turbulence au sein de l'interaction a été développé. Sa sensibilité aux conditions amont a été étudiée en plaçant des perturbations en amont de l'interaction. Dans tous les cas, des instationnarités convectives (haute fréquence) et stationnaires (basse fréquence) ont été observées et comparées à celles existantes pour les configurations amont turbulentes. Une gamme intermédiaire d'instationnarités convectives (moyenne fréquence) a été mise en évidence et caractériséeResearch dedicated to the study of the unsteadiness of turbulent Shock Wave Boundary Layer Interaction (SWBLI) has allowed a detailed description of this kind of interaction both experimentally and numerically. Several scenario were proposed to explain the low frequency unsteadiness observed in separated SWBLI. Nevertheless, the literature on this kind of flow involving either upstream laminar or transitional conditions is quite reduce. Within the framework of the European TFAST program, an important effort was made to develop experimental devices, in conjunction with numerical simulations, allowing a detailed study of these laminar or transitional configurations. In particular, within the framework of this thesis, a shock wave reflection configuration on a laminar boundary layer was set-up, with a nominal free stream Mach number of 1.68. Using classical metrology (Laser Doppler Anemometry, Hot WireAnemometry) that have been adapted to these particular experimental conditions, we have been able to describe the spatio-temporal properties of the interaction. The mean field has been characterized and compared with the classical theories and the results obtained in other configurations.A model describing the transition mechanisms to turbulence within the interaction has been developed. Its sensitivity to upstream conditions was studied by placing perturbations upstream of the interaction. In all cases, convective (high frequency) and stationary (low frequency) unsteadiness were observed and compared with those existing for upstream turbulent configurations. An intermediate range of convective unsteadiness (medium frequency) has been demonstrated and characterized
Livres sur le sujet "Laser-Doppler Anemometrie (LDA)"
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Zhang, Zhengji. LDA Application Methods : Laser Doppler Anemometry for Fluid Dynamics. Berlin, Heidelberg : Springer-Verlag Berlin Heidelberg, 2010.
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Węcłaś, Mirosław. Anemometria laserowa LDA w badaniach silników spalinowych. Poznań : Wydawn. Politechniki Poznańskiej, 1988.
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Zhang, Zhengji. LDA Application Methods : Laser Doppler Anemometry for Fluid Dynamics. Springer, 2010.
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Zhang, Zhengji. LDA Application Methods : Laser Doppler Anemometry for Fluid Dynamics. Springer, 2012.
Trouver le texte intégralChapitres de livres sur le sujet "Laser-Doppler Anemometrie (LDA)"
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Schuth, Michael, et Wassili Buerakov. « Laser-Doppler-Anemometrie (LDA/LDV) ». Dans Handbuch Optische Messtechnik, 265–69. München : Carl Hanser Verlag GmbH & Co. KG, 2017. http://dx.doi.org/10.3139/9783446436619.033.
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Durst, Franz, Adrian Melling et James H. Whitelaw. « Grundlagen der Laser-Doppler-Anemometrie (LDA) ». Dans Theorie und Praxis der Laser-Doppler-Anemometrie, 132–80. Karlsruhe : Braun-Verlag, 1987. http://dx.doi.org/10.1007/978-3-642-52132-4_4.
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Volkert, J., C. Tropea, R. Domann et W. Hübner. « Combined Application of Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA) to Swirling Flows Under Compression ». Dans Developments in Laser Techniques and Fluid Mechanics, 477–93. Berlin, Heidelberg : Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/978-3-642-60911-4_30.
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Sveen, J. K. « Laser Doppler anemometry (LDA) and particle image velocimetry (PIV) for marine environments ». Dans Subsea Optics and Imaging, 353–79. Elsevier, 2013. http://dx.doi.org/10.1533/9780857093523.3.353.
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Muguercia, I., E. Largaespada, W. LI et M. A. Ebadian. « FLUID FLOW BEHAVIOR INSIDE A CIRCULAR HELICOIDAL PIPE USING A LASER DOPPLER ANEMOMETRY/VELOCIMETRY (LDA/LDV) SYSTEM ». Dans Experimental Heat Transfer, Fluid Mechanics and Thermodynamics 1993, 958–65. Elsevier, 1993. http://dx.doi.org/10.1016/b978-0-444-81619-1.50118-0.
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De Padova, Diana, et Michele Mossa. « Hydrodynamics of Regular Breaking Wave ». Dans Geophysics and Ocean Waves Studies [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.94449.
Texte intégralRésumé :
Turbulence and undertow currents play an important role in surf-zone mixing and transport processes; therefore, their study is fundamental for the understanding of nearshore dynamics and the related planning and management of coastal engineering activities. Pioneering studies qualitatively described the features of breakers in the outer region of the surf zone. More detailed information on the velocity field under spilling and plunging breakers can be found in experimental works, where single-point measurement techniques, such as Hot Wire Anemometry and Laser Doppler Anemometry (LDA), were used to provide maps of the flow field in a time-averaged or ensemble-averaged sense. Moreover, the advent of non-intrusive measuring techniques, such as Particle Image Velocimetry (PIV) provided accurate and detailed instantaneous spatial maps of the flow field. However, by correlating spatial gradients of the measured velocity components, the instantaneous vorticity maps could be deduced. Moreover, the difficulties of measuring velocity due to the existence of air bubbles entrained by the plunging jet have hindered many experimental studies on wave breaking encouraging the development of numerical model as useful tool to assisting in the interpretation and even the discovery of new phenomena. Therefore, the development of an WCSPH method using the RANS equations coupled with a two-equation k–ε model for turbulent stresses has been employed to study of the turbulence and vorticity distributions in in the breaking region observing that these two aspects greatly influence many coastal processes, such as undertow currents, sediment transport and action on maritime structures.
Actes de conférences sur le sujet "Laser-Doppler Anemometrie (LDA)"
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Juling, Markus, Jonas Steinbock et Andreas Weissenbrunner. « Traceable Flow Rate Measurements With a Very Low Uncertainty Using Laser Doppler Anemometry ». Dans ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69278.
Texte intégralRésumé :
Precise volume flow rate measurements are very important for various industrial applications. Here, one problem is that the service conditions of a flow meter used in the field differ significantly from the conditions present during calibration. The working conditions such as the pressure, the temperature and the flow profile greatly increase the uncertainty of the flow rate measurement. To address this problem, a new laser-optical flow rate standard (LFS) was developed at the Physikalisch-Technische Bundesanstalt (PTB) that allows flow meters to be calibrated on site, thus greatly reducing the uncertainty of the flow rate measurement. For the LFS, the velocity profile within the pipe is measured with laser Doppler anemometry (LDA). The profile is then integrated to calculate the volume flow rate. Various improvements to LDA have made it possible to measure the flow rate with an uncertainty of less than 0.15 % (k = 2). A comparison of the LFS with the primary standard for thermal energy at PTB, which has an uncertainty of less than 0.04 % (k = 2), revealed a maximum deviation of 0.07 % for Reynolds numbers from 105 to 106, thus verifying the uncertainty of the LFS.
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Jalili, Vahid, Mayur K. Patel, Christopher Bailey, Steve Begg, Henk Versteeg, Ian Shrubb et Graham Hargrave. « Design Analysis of the Volumatic : A CFD and Experimental Study ». Dans ASME 2002 Pressure Vessels and Piping Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/pvp2002-1555.
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The aim of this paper has been to describe the novel approach adopted in studying the flow field within the Volumatic. In this study a combination of engineering tools such as Computational Fluid Dynamics (CFD), Laser Doppler Anemometry (LDA) and Flow visualization techniques have been employed. The initial part of the study involved the use of CFD in modelling the drug entering the Volumatic. The CFD model was then validated against measurements made using LDA. The agreement obtained was very good; this was particularly encouraging as the CFD analysis was carried out some six months prior to the experimental study.
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Becker, Julian, et Christoph Hassa. « Experimental Investigation of Spatial and Temporal Aspects of the Liquid Fuel Placement in a Swirl Cup at Elevated Pressure ». Dans ASME Turbo Expo 2004 : Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53524.
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The kerosene spray generated by a pressure swirl fuel nozzle embedded in a swirling airflow in a swirl cup typical of aeroengine combustors was investigated at different levels of air pressure to assess the counter-acting effects of increasing air density and transfer of centrifugal momentum from airflow to spray. Hardware parameters investigated included air swirl angle and fuel nozzle flow number. Measurement techniques included spray visualization, Phase-Doppler Anemometry (PDA) for spray analysis and Laser-Doppler Anemometry (LDA) for investigation of the air flow field. Operating conditions for PDA measurements were 6, 12, and 18 bar at 700 K. Spray visualizations and LDA measurements were performed at scaled operating conditions. It was found that fuel placement is governed by the presence or absence of a recirculation zone inside the swirl cup and hence by the swirl angle of the airflow. Analysis of temporal aspects of the spray showed the existence of droplet clusters. Configurations characterized by strong swirl furthermore exhibited a preferred frequency of inter-particle times.
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Morvan, D., F. Krayem, S. Magnaval, S. F. Miralai, J. Amouroux, D. Ballutaud, S. Dresvin et S. Nguen Kuok Shy. « Deposition of Thick Silicon Layers Using a Radio-Frequency Thermal Plasma ». Dans ITSC 1998, sous la direction de Christian Coddet. ASM International, 1998. http://dx.doi.org/10.31399/asm.cp.itsc1998p0511.
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Abstract RF Ar-H2 plasma spraying of metallurgical grade silicon particles (80-125 µm) was used in order to combine the purification and the deposition process of silicon particles with a high deposition rate (300 - 600 µm). The hydrogen and oxygen content of the plasma gas turned out to be of a great importance to purify metallurgical silicon powders. The whole process was investigated through ex-situ characterisation of the deposits and on-line diagnostics of the plasma which results matched quite well with the mathematical modelling. The deposits were characterised using SEM, EDX analysis, SIMS, XPS in order to explain the composition and overall properties of the layers in view of their use in photovoltaic applications. Characterisation of silicon deposits was completed by the hydrogen rate analysis using exodiffusion method. Hydrogen trapping in plasma sprayed deposits was found in order of 1019 at/cm3. The oxygen contained in the original powders (30%) was decreased down to 3 - 5% in the deposits. Finally, the on-line diagnostics of the plasma used was : Laser Doppler Anemometry (LDA), Laser Doppler Granulometry (LDG) and Optical Emission Spectroscopy (OES). The mean velocity and surface temperature of particles was found to be in agreement with modelling results.
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Smith, David S., Francis Loth, Hisham S. Bassiouny, Paul Fischer, Jennifer K. Grogan et Sang-Wook Lee. « Velocity Measurements Inside a Hemodialysis Graft In Vitro Model ». Dans ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-62031.
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Arteriovenous (AV) grafts, which provide an access site for hemodialysis, typically produce a high flow rate environment with pressure and velocity fluctuations; high and low wall shear stress, and vibration. Laser Doppler anemometry (LDA) was performed at Reynolds number (Re) 1200 on an in vitro model, which was constructed from computerized tomography (CT) images of a perfusion fixed plastic cast of a canine venous anastomosis. The results obtained were compared to numerical results and to results previously obtained with idealized in vitro models. This study showed the importance of an accurate geometry in characterizing the flow environment inside an AV graft. Good agreement between the computational fluid dynamics (CFD) and LDA was observed although differences were clearly present.
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Behrendt, Thomas, Johannes Heinze et Christoph Hassa. « Experimental Investigation of a New LPP Injector Concept for Aero Engines at Elevated Pressures ». Dans ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38444.
Texte intégralRésumé :
A new LPP injector concept for aero engines is presented. The design target was to achieve a fine atomization in order to get a high degree of prevaporization. Inside the injector atomization and mixture homogenization are spatially separated allowing for an individual optimization. The injector was operated in an optical accessible single sector combustor at elevated pressures. The reacting two phase flow was investigated by means of Laser Doppler Anemometry (LDA), Phase Doppler Anemometry (PDA), visualisation of OH* chemiluminescence, kerosene LIF and Mie scattering and OH LIF. The spatially and temporally resolved temperature distribution was calculated from the OH LIF images. The influence of the air preheat temperature on emissions was examined by applying conventional exhaust gas analysis. The results of the optical measurement techniques were used for an analysis of the reacting flow field and for the interpretation of the influence of the preheat temperature.
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Al-Hajeri, M. H., Raed Al-Saleh, Adel Al-Hebeshi et Ali Witry. « Cold Flow Investigation of Silicon Carbide Cylindrical Filter Element ». Dans ASME Turbo Expo 2002 : Power for Land, Sea, and Air. ASMEDC, 2002. http://dx.doi.org/10.1115/gt2002-30589.
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Silicon carbide cylindrical filter elements have proven to be an effective mean of removing particulates to levels exceeding the new source performance standard. This paper reports a Laser Doppler anemometry (LDA) investigation to study the flow behavior in the vicinity of the cylindrical filter. A single cylindrical filter has based in vertical channel. The flow enters from the bottom of the channel towards the filter element passing through to the outlet at the top of the channel. The particles deposition distribution around the filter element is studied using different face velocities.
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Arruda, M. P., et N. Lawson. « Experimental and Computational Investigation on Submerged Entry Nozzle Jet Control ». Dans ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45243.
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Two-dimensional Laser Doppler anemometry (LDA) and computational fluid dynamics (CFD) are used to investigate the influence of cross-flow and momentum addition on flow features of a submerged entry nozzle (SEN) jet in a rectangular cavity (Rejet ≈ 95000). Round sidewall control jets are used to attempt to deflect and attenuate the main jet oscillation (St,W = 0.012). Feedback loop flow manipulation by injecting in the cross-flow region has shown to be an effective control configuration and a steady deflected jet has been computationally achieved. Higher control sensitivity has been observed for a variation on lateral jet momentum rather than for a variation of mass rate injected.
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Bailey, Gearle, et John Kuhlman. « Intake Turbulence Generated by a Steady Valve-Cylinder Flow ». Dans ASME 2002 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/icef2002-498.
Texte intégralRésumé :
Axial and swirl velocities have been measured for steady axisymmetric flow in a cylinder past a fixed intake valve located on the cylinder centerline, for two different intake port geometries and two valve lifts, in order to study the effects of swirl and valve lift on turbulence generation. Both Laser Doppler Anemometry (LDA) and Constant Temperature Anemometry (CTA) velocity measurements were obtained. The cylinder diameter was 82.6 mm, cylinder height was 114.3 mm, and the centrally located valve had a diameter of 41.9 mm. The LDA mean axial velocity data indicated a conical jet issuing from the valve, and a recirculating toroidal vortex above the valve for each case. Also, for the swirl intake cases, the swirl mean velocity in the toroidal vortex increased linearly with radius. Axial fluctuation velocities were about 1 m/sec away from the conical jet, for both valve lifts and both inlet flow geometries. In the conical jet, axial fluctuation velocities of 2–2.5 m/sec were observed. The swirl fluctuation was consistently lower than the axial fluctuation. The swirl inlet increased the magnitude of the swirl fluctuation in the conical jet.
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Hassa, Christoph, Chris Willert, Michael Fischer, Guido Stockhausen, Ingo Ro¨hle, Wolfgang Meier, Lorin Wehr et Peter Kutne. « Nonintrusive Flowfield, Temperature and Species Measurements on a Generic Aeroengine Combustor at Elevated Pressures ». Dans ASME Turbo Expo 2006 : Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90213.
Texte intégralRésumé :
A generic combustor was built, that gives wide optical access at higher pressure and shares typical features with aero engine combustors. A comprehensive data set for validation of RANS and LES codes was generated at isothermal as well as combusting conditions at 2 and 10 bars with 650 K preheat using natural gas as fuel. The velocity field was measured using LDA (Laser Doppler Anemometry) and DGV (Doppler Global Velocimetry) as well as PIV (Particle Image Velocimetry). Temperature data were acquired using CARS (Coherent Anti stokes Raman Scattering) and SRS (Spontaneous Raman Scattering). Major species concentrations as well as the mixture fraction in the primary zone of the combustor were also measured using SRS. Mean and RMS values of the temperature measured by CARS in the secondary zone illustrate the influence of the jet impingement on the unsteady mixing of the jets with the swirling primary air.