Articles de revues : « 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, n^o 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, n^o 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, n^o 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, n^o 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, n^o 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, n^o 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, n^o 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.

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Sideris, M. Th, et R. A. Van den Braembussche. « Influence of a Circumferential Exit Pressure Distortion on the Flow in an Impeller and Diffuser ». Journal of Turbomachinery 109, n^o 1 (1 janvier 1987) : 48–54. http://dx.doi.org/10.1115/1.3262069.

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Detailed velocity measurements, using Laser Doppler Anemometry (LDA) and static pressure measurements in the vane/ess diffuser of a centrifugal compressor, are presented. They show the relation between the circumferential variation of the pressure and the local flow in the diffuser and at the impeller exit. Theoretical calculations using an impeller-diffuser interaction model have been made. A comparison between the theoretical results and experimental data allows an evaluation of the possibilities and shortcomings of such a calculation. It also illustrates the mechanisms by which the variation of the impeller outlet velocity is defined.

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Sun, Xiaodong, Sidharth Paranjape, Seungjin Kim, Hiroshi Goda, Mamoru Ishii et Joseph M. Kelly. « Local Liquid Velocity in Vertical Air-Water Downward Flow ». Journal of Fluids Engineering 126, n^o 4 (1 juillet 2004) : 539–45. http://dx.doi.org/10.1115/1.1777235.

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This paper presents an experimental study of local liquid velocity measurement in downward air-water bubbly and slug flows in a 50.8 mm inner-diameter round pipe. The axial liquid velocity and its fluctuations were measured by a laser Doppler anemometry (LDA) system. It was found that the maximum liquid velocity in a downward two-phase flow could occur off the pipe centerline at relatively low liquid flow rates and this observation is consistent with other researchers’ results. The comparisons between the liquid flow rates measured by a magnetic flow meter and those obtained from the local LDA and multi-sensor conductivity probe measurements showed good agreement. In addition, based on the local measurements the distribution parameter and the drift velocity in the drift-flux model were obtained for the current downward flow tests.

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Roberts, J. B., et A. D. M. Hilton. « A direct transform method for the analysis of laser Doppler anemometry engine data ». Proceedings of the Institution of Mechanical Engineers, Part D : Journal of Automobile Engineering 215, n^o 6 (1 juin 2001) : 725–38. http://dx.doi.org/10.1243/0954407011528301.

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A new, computationally efficient method of fitting a specific parametric stochastic model of in-cylinder flow to real laser Doppler anemometry (LDA) internal combustion engine data, obtained either at a single position in space or over a range of spatial positions at effectively one point in the engine cycle (scanning data) is proposed. The model, which is fully specified in terms of a set of parameters, assumes that the velocity variations can be modelled as the sum of an ensembleaveraged mean component, a non-stationary ‘turbulence’ component and a random ‘cycle-to-cycle’ component, the last of these being phase locked to the engine cycles. The fitting technique is based on a direct transform of the velocity data obtained in each cycle and leads to an identification of the mean-square magnitudes of the turbulence and cycle-to-cycle components. A unique advantage of this approach is that it is possible to determine, theoretically, confidence limits for the estimates of the statistics of the fluctuation components. This provides a theoretical means of designing experiments to achieve a prescribed level of accuracy. The estimation method, and the theoretical determination of confidence limits, is validated initially through application to some simulated data which fully capture all the characteristics inherent in real data. Finally some results of analysing real in-cylinder LDA data, of the scanning type, are presented. Although the approach proposed here is applied to a particular model of in-cylinder flow it is, in principle, extendable to other models.

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Fraser, S. M., A. M. Abdel-Razek et M. Z. Abdullah. « Computational and experimental investigations in a cyclone dust separator ». Proceedings of the Institution of Mechanical Engineers, Part E : Journal of Process Mechanical Engineering 211, n^o 4 (1 novembre 1997) : 247–57. http://dx.doi.org/10.1243/0954408971529719.

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Three-dimensional turbulent flow in a model cyclone has been simulated using PHOENICS code and experimental studies carried out using a laser Doppler anemometry (LDA) system. The experimental results were used to validate the computed velocity distributions based on the standard and a modified k-∊ model. The standard k-∊ model was found to be unsatisfactory for the prediction of the flow field inside the cyclone chamber. By considering the strong swirling flow and the streamlined curvature, a k-∊ model, modified to take account of the Richardson number, provided better velocity distributions and better agreement with the experimental results.

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Algieri, Angelo, Sergio Bova et Carmine De Bartolo. « Experimental and Numerical Investigation on the Effects of the Seeding Properties on LDA Measurements ». Journal of Fluids Engineering 127, n^o 3 (1 mars 2005) : 514–22. http://dx.doi.org/10.1115/1.1899167.

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The characteristics of the seeding particles, which are necessary to implement the laser Doppler anemometry (LDA) technique, may significantly influence measurement accuracy. LDA data were taken on a steady-flow rig, at the entrance of the trumpet of the intake system of a high-performance engine head. Five sets of measurements were carried out using different seeding particles: samples of micro-balloons sieved to give three different size ranges (25–63μm,90–200μm, and standard as received from the manufacturer 1–200μm), smoke from a “home-made” sawdust burner (particle size ⩽1μm), and fog from a commercial device (particle size around 1μm). The LDA data were compared with the results of two-phase computational fluid dynamics simulations. The comparison showed a very good agreement between the experimental and numerical results and confirmed that LDA measurements with particle dimensions in the order of 1μm or less represent the actual gas velocity. On the contrary, quite large particles, which are often used because of their cost and cleanliness advantages, introduce non-negligible errors.

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Strakey, Peter. « Review of "LDA Application Methods : Laser Doppler Anemometry for Fluid Dynamics (Experimental Fluid Dynamics)" ». AIAA Journal 50, n^o 1 (janvier 2012) : 254. http://dx.doi.org/10.2514/1.j051007.

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Sayeed-Bin-Asad, S. M., T. S. Lundström, A. G. Andersson et J. G. I. Hellström. « Velocity distribution measurements in a fishway like open channel by Laser Doppler Anemometry (LDA) ». EPJ Web of Conferences 114 (2016) : 02005. http://dx.doi.org/10.1051/epjconf/201611402005.

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Kysela, Bohuš, Jiří Konfršt, Ivan Fořt, Michal Kotek et Zdeněk Chára. « Study of the Turbulent Flow Structure around a Standard Rushton Impeller ». Chemical and Process Engineering 35, n^o 1 (1 mars 2014) : 137–47. http://dx.doi.org/10.2478/cpe-2014-0010.

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Abstract The velocity field around the standard Rushton turbine was investigated by the Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV) measurements. The mean ensembleaveraged velocity profiles and root mean square values of fluctuations were evaluated at two different regions. The first one was in the discharge stream in the radial direction from the impeller where the radial flow is dominant and it is commonly modelled as a swirling turbulent jet. The validity range of the turbulent jet model was studied. The second evaluated region is under the impeller where flow seems to be at first sight rather rigorous but obtained results show nonnegligible values of fluctuation velocity.

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Lam, Wei-Haur, Yongchen Song, Srinivasan Raghunathan, Gerard Hamill et Desmond Robinson. « Investigation of a ship's propeller jet using momentum decay and energy decay ». Canadian Journal of Civil Engineering 38, n^o 6 (juin 2011) : 605–15. http://dx.doi.org/10.1139/l11-028.

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Previous researchers use the velocity decay as an input to investigate the ship’s propeller jet induced scour. A researcher indicated that most of the equations used to predict the stability of various protection systems are often missing a physical background. The momentum decay and energy decay are currently proposed as an initial input for seabed scouring investigation, which are more sensible in physics. Computational fluid dynamics (CFD) and laser Doppler anemometry (LDA) experiments are used to obtain the velocity data and then transforming into momentum and energy decays. The findings proposed several exponential equations of velocity, momentum and energy decays to estimate the region exposed to the seabed scouring.

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Fatemi, R., et K. B. Chandran. « An In Vitro Comparative Study of St. Jude Medical and Edwards-Duromedics Bileaflet Valves Using Laser Anemometry ». Journal of Biomechanical Engineering 111, n^o 4 (1 novembre 1989) : 298–302. http://dx.doi.org/10.1115/1.3168382.

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An in vitro comparative study of St. Jude (SJ) and Edwards-Duromedics (DM) Bileaflet valves was performed under steady and physiological pulsatile flow conditions in an axisymmetric chamber using Laser Doppler Anemometry (LDA). LDA measurements were conducted in two different orientations; in the first orientation, the LDA traverse was perpendicular and, in the second orientation, parallel to the tilt axis of the leaflets. The axial velocities were measured in both orientations at two different locations distal to the valves. The velocity profiles at peak systole show the presence of stronger vortex in the sinus region for flow past SJ valve in the first orientation compared to the DM valve. Velocity profile distal to the SJ valve in second orientation was relatively flat where as for the DM valve, a jet-like flow was present. The differences found in the velocity profiles between the two valves can be attributed to the differences in geometry with thicker leaflets, smaller angle of leaflets opening and the presence of the leaflet curvature for the DM valve. The results obtained in this study do not show any fluid dynamic advantages due to the curved leaflet geometry of the DM valve.

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Ammerman, C. N., et S. M. You. « Consecutive-Photo Method to Measure Vapor Volume Flow Rate During Boiling From a Wire Immersed in Saturated Liquid ». Journal of Heat Transfer 120, n^o 3 (1 août 1998) : 561–67. http://dx.doi.org/10.1115/1.2824311.

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A photographic measurement technique is developed to quantify the vapor volume flow rate departing from a wire during boiling. The vapor flow rate is determined by measuring the volume of bubbles after departure from the boiling surface in consecutive frames of high-speed video. The measurement technique is more accurate and easier to implement than a previously developed photographic/laser Doppler anemometry (LDA) method. Use of the high-speed camera in place of a standard video camera eliminates the requirement for LDA-acquired bubble velocity measurements. The consecutive-photo method requires relatively few video images to be analyzed to obtain steady-state vapor volume flow rates. The volumetric flow rate data are used to calculate the latent heat transfer and, indirectly, sensible heat transfer which comprise the nucleate boiling heat flux. The measurement technique is applied to a 75-μm diameter platinum wire immersed in saturated FC-72.

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Ammerman, C. N., S. M. You et Y. S. Hong. « Identification of Pool Boiling Heat Transfer Mechanisms From a Wire Immersed in Saturated FC-72 Using a Single-Photo/LDA Method ». Journal of Heat Transfer 118, n^o 1 (1 février 1996) : 117–23. http://dx.doi.org/10.1115/1.2824024.

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A unique method to determine the vapor volumetric flow rate above a heated wire utilizing a single photograph and laser-Doppler anemometry is developed and discussed. The volumetric flow rate is combined with additional analyses to determine the overall contributions to the total heat flux from four nucleate boiling heat transfer mechanisms (latent heat, natural convection, Marangoni flow, and microconvection). This method is applied to a 75-μm wire immersed in a saturated, highly wetting liquid (FC-72). Latent heat is identified as the dominant mechanism in the fully developed nucleate boiling regime.

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Guillot, Dominique, et Alain Dunand. « Rheological Characterization of Fracturing Fluids by Using Laser Anemometry ». Society of Petroleum Engineers Journal 25, n^o 01 (1 février 1985) : 39–45. http://dx.doi.org/10.2118/12030-pa.

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Abstract In this paper we describe the use of a novel technique, laser Doppler anemometry (LDA), to obtain information on fracturing fluid behavior. This technique permits measurement of fluid velocity at any point in a flow system. By scanning across the flow geometry, it is possible to obtain the velocity profile, which is related, possible to obtain the velocity profile, which is related, in turn, to the rheology of the fluid. At low shear rates, velocity profiles obtained for aqueous solutions of hydroxypropyl guar showed significant deviations from those calculated using known power law parameters. The investigation was extended by power law parameters. The investigation was extended by conducting a series of rheological experiments using rotational and capillary viscometers over a wide shear-rate range (10(–2) to 2 × 10(3) seconds (–1)) The data have been fitted to a three-parameter Ellis model, and the velocity profiles calculated from these data agree well with profiles calculated from these data agree well with experimental ones. The immediate results of this work are of interest in proppant transport modeling and correlate well with proppant transport modeling and correlate well with published data that show that apparent viscosities obtained published data that show that apparent viscosities obtained from proppant settling velocities are lower than those obtained from power law parameters. Introduction The role played by the rheology of fracturing fluids in the design of stimulation treatments does not need to be stressed. Friction pressure through pipes and/or annuli, fracture geometry, and proppant placement depend primarily on the rheological properties of treating fluids. primarily on the rheological properties of treating fluids. Fracturing fluids usually exhibit a non-Newtonian behavior. Under isothermal conditions, their rheological properties may be shear-dependent only, as in linear gels, properties may be shear-dependent only, as in linear gels, or much more complex (i.e., time/shear-dependent), as in the case of crosslinked gels. Several types of rheometers have been used to characterize the behavior of fracturing fluids: coaxial cylinder viscometers, cone and plate rheometers, and capillary viscometers. These traditional means of evaluating non-Newtonian rheology are subject to several drawbacks inherent in the measuring technique itself or in the type of fluid under study. For instance, coaxial cylinder and capillary viscometers do not allow for the direct computation of the shear rate that is applied to measured fluids. For a time-independent non-Newtonian fluid, a proper interpretation of the measurements must involve the determination of the first, or even higher order, derivative of the experimental curve Copyright 1985 Society of Petroleum Engineers (rotational speed/torque or flow-rate/pressure-drop curves). The time-dependent nature of some fluids complicates the problem, since, in these viscometers, fluid particles experience different shear rates and, therefore, particles experience different shear rates and, therefore, different shear histories. On the experimental side, difficulties may arise from the three-dimensional structure and from the correlative elasticity of crosslinked fluids-e.g., the Weissenberg effect in coaxial cylinder viscometers or the ejection of the fluid from cone and plate rheometers in steady rotation even at low speeds. Some of the limitations encountered in the rheological characterization of time-dependent fracturing fluids may be overcome with an improved experimental techniqueLDA. LDA is a direct and nondestructive technique for measuring particle velocities in a moving fluid. Therefore, it allows characterization of the flow kinematics. The technique was tested first on the simplest case of a time-independent fluid to evaluate its validity for fracturing rheological studies. In the following sections, after a description of the LDA technique and of the equipment, we illustrate the use of the LDA by the study of a noncrosslinked fluid that has been characterized using classical rheometrical methods. We stress the importance of the frequently forgotten Newtonian behavior of these linear gels at low shear rates. Implication of the results on the design of fracturing treatments also is discussed. The LDA Technique Principle LDA uses the Doppler shift of light scattered Principle. LDA uses the Doppler shift of light scattered by moving particles in a flow system to determine particle velocity and thus measure the fluid velocity at a given point. In dual-beam mode, the most common technique, two point. In dual-beam mode, the most common technique, two coherent laser beams of equal intensity intersect, and light scattered in any one direction is picked up by a photodetector (Fig. 1). The difference, fD, between the photodetector (Fig. 1). The difference, fD, between the two scattering frequencies, fsi and fs2 is independent of the scattering direction, es, and proportional to a velocity component, Vx, of the particles flowing through the beam intersection (Fig. 2). LDA has the great advantage of being a direct and nonperturbative velocimetry technique in that only light beams enter the flow through a transparent window. No flow calibration is required, and no probe (hot wire, turbine) is necessary inside the flow, thereby eliminating any disturbances. SPEJ P. 39

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Johnson, David A. « Analysis of the Immediate Boundary Conditions of an Axial Flow Impeller ». Journal of Fluids Engineering 123, n^o 4 (8 août 2001) : 771–79. http://dx.doi.org/10.1115/1.1412846.

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The design and analysis of impellers for mixing applications such as stirred tank reactors (STR) have significant application in many engineering processes. In particular, the evaluation of the turbulent flow boundary conditions immediately around a model impeller has been examined using flow visualization, laser Doppler anemometry (LDA) and particle image velocimetry (PIV). Mean and fluctuating velocities are presented for all three velocity components. Good agreement between LDA and PIV measurements was obtained once an optimized PIV arrangement was defined. Turbulence parameters such as kinetic energy, dissipation, and length scales are estimated from the measurements. Several approaches to evaluating dissipation were used. Triggered PIV measurements were used to evaluate the variation in radial and tangential velocities in the entire planes above and below the impeller at constant axial distances. The size and orientation of the vortices shed from the impeller blade tips and the corresponding regions of high kinetic energy and dissipation indicate the importance of these structures in mixing.

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Flamang, P., et R. Sierens. « Study of the Steady-State Flow Pattern in a Multipulse Converter by LDA ». Journal of Engineering for Gas Turbines and Power 110, n^o 3 (1 juillet 1988) : 515–22. http://dx.doi.org/10.1115/1.3240165.

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This paper describes pressure and velocity measurements on a multipulse converter under steady-state conditions. Pressure loss coefficients were measured on this four-entry pulse converter system for a large number of flow configurations. Three-dimensional velocity measurements were done (with Laser-Doppler anemometry) for several flow configurations and at different cross sections in the converter. The normal flow situation (incoming flow at the four entries) and back flow situations were examined. For each cross section the axial velocity profiles, the secondary flow patterns, and the turbulent velocities are presented. From the pressure measurements mixing losses are derived. These are compared with the results of a one-dimensional calculation, which is based on the impulse law for incompressible flow. Taking into account the velocity measurements, this simplified model gives a remarkable agreement with the measured mixing losses.

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Azimian, M., M. Lichti et H. J. Bart. « Investigation of Particulate Flow in a Channel by Application of CFD, DEM and LDA/PDA ». Open Chemical Engineering Journal 8, n^o 1 (21 février 2014) : 1–11. http://dx.doi.org/10.2174/1874123101408010001.

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Hydroabrasion in particulate flows plays an important role in various industrial and natural processes. To predict the influence of it in a pipeline, channel or a fitting, it is essential to characterize the effects in a simple standardized geometry. An example to this is a pipe channel with a cylindrical obstacle adjusted inside the channel perpendicular to the flow direction. Results of flow field are generated by using the non-invasive Laser/Phase Doppler Anemometry (LDA/PDA) measurement technique. The velocity profiles of single phase and particulate flow from computational fluid dynamics (CFD) and discrete element method (DEM) simulations were validated by the LDA experimental data. The simulations were performed on the basis of Euler-Lagrange technique for both CFD and DEM. The measurements show that a Karman vortex field forms behind the obstacle and particles move inside this field with an average negative velocity of up to 25% of the fully developed velocity field. A comparison of CFD and DEM results with experimental data showed that in Karman velocity field, the CFD results fit better to the LDA measurements. In the fully developed flow region and also above and under the vortex field behind the obstacle, the DEM results match better with the LDA data.

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Lawson, N. J., J. M. Eyles et K. Knowles. « Particle image velocimetry and laser Doppler anemometry experimental studies of a compressible short take-off and vertical landing ground vortex flow ». Proceedings of the Institution of Mechanical Engineers, Part G : Journal of Aerospace Engineering 216, n^o 4 (1 avril 2002) : 171–87. http://dx.doi.org/10.1243/09544100260369713.

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A particle image velocimetry (PIV) and laser Doppler anemometry (LDA) study of a scaled short take-off and vertical landing (STOVL) ground vortex flow is presented. The scaled flow features a compressible impinging jet in cross-flow with a moving ground plane. Mean and transient PIV and LDA velocity data are recorded from the ground vortex about the jet centre-line over a range of nozzle pressure ratios (NPR s) from 2.3 to 3.7, nozzle height—diameter ratios ( h/dn) from 3 to 10 (where dn = 12.7 mm) and cross-flow velocities (V∞) from 10 to 20 m/s, corresponding to effective velocity ratios of 19 < Ve−1 < 38. For each condition, 72 PIV vector maps were taken from the ground vortex region to generate an instantaneous and time-average data set. From the instantaneous data, a cinematic sequence was used to track the ground vortex position, which was found to fluctuate longitudinally by a root mean square distance of up to 4.47 dn and vertically by up to 2.18 dn. From the time-averaged PIV measurements, selected LDA pointwise data were taken at the average ground vortex core. Subsequent spectral analysis of the PIV time series showed the ground vortex position to fluctuate at dominant frequencies of between 2.5 and 5 Hz while the LDA data showed the velocity to fluctuate by dominant frequencies ranging between 1 and 30 Hz.

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Becker, S., C. M. Stoots, K. G. Condie, F. Durst et D. M. McEligot. « LDA-Measurements of Transitional Flows Induced by a Square Rib ». Journal of Fluids Engineering 124, n^o 1 (8 août 2001) : 108–17. http://dx.doi.org/10.1115/1.1446067.

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New fundamental measurements are presented for the transition process in flat plate boundary layers downstream of two-dimensional square ribs. By use of laser Doppler anemometry (LDA) and a large Matched-Index-of-Refraction (MIR) flow system, data for wall-normal fluctuations and Reynolds stresses were obtained in the near wall region to y+<0.1 in addition to the usual mean streamwise velocity component and its fluctuation. By varying velocity and rib height, the experiment investigated the following range of conditions: k+=5.5 to 21, 0.3<k/δ1<1,180<Rek<740,6×104<Rex,k<1.5×105,ReΘ660,−125<x−xk/k<580. Consequently, results covered boundary layers which retained their laminar characteristics through those where a turbulent boundary layer was established shortly after reattachment beyond the forcing rib. For “large” elements, evolution of turbulent statistics of the viscous layer for a turbulent boundary layer y+<∼30 was rapid even in flows where the mean velocity profile still showed laminar behavior.

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Beauquel, J., S. Ibrahim et R. Chen. « Validation of in-cylinder flow structure of controlled auto-ignition engine ». World Journal of Engineering 10, n^o 4 (21 août 2013) : 305–12. http://dx.doi.org/10.1260/1708-5284.10.4.305.

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Numerical calculations have been carried out to investigate the in-cylinder transient flow structure of a controlled auto-ignition (CAI) engine running at speeds of 1,500rpm and 2,000rpm. The calculated turbulent flow structure and velocities are validated against published laser doppler anemometry (LDA) experimental data. The experimental data were re-processed to represent the time dependent mean velocities for all measured points. The actual geometry configuration of the engine is imported into the computational fluid dynamics (CFD) code used in this study. The simulations take into account the movement of the inlet, exhaust valves and the piston. The CFD simulations replicate the experimental work where only air was inserted into a driven optical engine. Also, to simulate an engine in controlled auto-ignition (CAI) mode, the same valve timing that allows 36% internal exhaust gas recirculation (IEGR) was applied for the air intake. The calculated results are found to agree well with the LDA measurements with an overall agreement of 75.06% at 1,500 rpm and 73.42% at 2,000 rpm.

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Beauquel, J., S. Ibrahim et R. Chen. « Validation of in-cylinder flow of a controlled auto-ignition engine ». World Journal of Engineering 11, n^o 4 (1 août 2014) : 421–30. http://dx.doi.org/10.1260/1708-5284.11.4.421.

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Numerical calculations have been carried out to investigate the in-cylinder transient flow structure of a controlled auto-ignition (CAI) engine running at speeds of 1500 rpm and 2000 rpm. The calculated turbulent flow structure and velocities are validated against published laser doppler anemometry (LDA) experimental data (Pitcher et al., 2003). The experimental data was reprocessed to represent the time dependent mean velocities for all measured points. The actual geometry configuration of the engine is imported into the computational fluid dynamics (CFD) code used in this study. The simulations take into account the movement of the inlet, exhaust valves and the piston. The CFD simulations replicate the experimental work where only air was inserted into a driven optical engine. Also, to simulate an engine in controlled auto-ignition (CAI) mode, the same valve timing that allows 36% internal exhaust gas recirculation (IEGR) was applied for the air intake. The calculated results found to agree well with the LDA measurements with an overall agreement of 75.06% at 1500 rpm and 73.42% at 2000 rpm.

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Algieri, Angelo, Sergio Bova et Carmine De Bartolo. « Influence of Valve Lift and Throttle Angle on Intake Flow in a High-Performance Four-Stroke Motorcycle Engine ». Journal of Engineering for Gas Turbines and Power 128, n^o 4 (9 janvier 2006) : 934–41. http://dx.doi.org/10.1115/1.2180277.

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A high-performance four-stroke motorcycle engine was analyzed at a steady flow rig. The aim of the work was to characterize the fluid dynamic behavior of the engine head during the intake phase. To this purpose a twofold approach was adopted: the dimensionless flow coefficient was used to evaluate the global breathability of the intake system, while the laser doppler anemometry (LDA) technique was employed to define the flow structure within the combustion chamber. The analysis gave evidence of two contrarotating vortices with axes parallel to the cylinder axis and showed variations in the flow structure when moving away from the engine head. Furthermore, the study highlighted the great influence of the throttle angle on the head fluid dynamic efficiency and how this influence changes with the valve lift. Experimental data were correlated by a single curve adopting a new dimensionless plot. Moreover, LDA measurements were used to evaluate the angular momentum of the flux and an equivalent swirl coefficient, and to correlate them to a previous global swirl characterization carried out on the same engine head using an impulse swirl meter.

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SHEEN, H. J., W. J. CHEN et J. S. WU. « Flow patterns for an annular flow over an axisymmetric sudden expansion ». Journal of Fluid Mechanics 350 (10 novembre 1997) : 177–88. http://dx.doi.org/10.1017/s0022112097006794.

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In this paper, an experimental investigation is described for a concentric annular flow over an axisymmetric sudden expansion by using both flow visualization and laser-Doppler anemometry (LDA) techniques. Depending upon the value of the Reynolds number and whether the Reynolds number was increased or decreased, four typical flow patterns were classified according to the characteristics of the central and corner recirculation zones. The flow patterns are open annular flow, closed annular flow, vortex shedding, and stable central flow. Bifurcation for this flow occurred when 230 < Re < 440, which was verified by observing the variation of the reattachment length. The spatial growth of velocity fluctuations from the measurements demonstrated a tendency that shedding vortices behind the centrebody more strongly affect the reattachment length than flows without a centrebody.

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Stieger, R. D., et H. P. Hodson. « Unsteady dissipation measurements on a flat plate subject to wake passing ». Proceedings of the Institution of Mechanical Engineers, Part A : Journal of Power and Energy 217, n^o 4 (1 janvier 2003) : 413–19. http://dx.doi.org/10.1243/095765003322315478.

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Boundary layer measurements were performed on a flat plate with an imposed pressure gradient typical of a high-lift low-pressure (LP) turbine blade and subject to incoming turbulent wakes shed from a moving bar wake generator. A multiple-orientation one-dimensional laser doppler anemometry (LDA) technique was used to measure the ensemble-average mean flow and Reynolds stresses. These ensembleaverage measurements were used to calculate the boundary layer dissipation, thereby providing unprecedented experimental evidence of the loss-reducing mechanisms associated with wake-induced transition. The benign character of the calmed zone was confirmed and the early stages of boundary layer separation were found to have laminar levels of dissipation. A deterministic natural transition phenomenon was identified between wake passing events, highlighting the existence of natural transition phenomena in LP turbine style pressure distributions.

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KUIK, D. J., C. POELMA et J. WESTERWEEL. « Quantitative measurement of the lifetime of localized turbulence in pipe flow ». Journal of Fluid Mechanics 645 (22 février 2010) : 529–39. http://dx.doi.org/10.1017/s0022112009993065.

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Transition to turbulence in a pipe is characterized by the increase of the characteristic lifetimes of localized turbulent spots (‘puffs’) with increasing Reynolds number (Re). Previous experiments are based on visualization or indirect measurements of the lifetime probability. Here we report quantitative direct measurements of the lifetimes based on accurate pressure measurements combined with laser Doppler anemometry (LDA). The characteristic lifetime is determined directly from the lifetime probability. It is shown that the characteristic lifetime does not diverge at finite Re, and follows an exponential scaling for the observed range 1725 ≤ Re ≤ 1955. Over this small Re range the lifetime increases over four orders of magnitude. The results show that the puff velocity is not constant, and the rapid disintegration of puffs occurs within 20–70 pipe diameters.

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Kyriakides, S. C., et A. R. Glover. « A Study of the Correlation between In-Cylinder Air Motion and Combustion in Gasoline Engines ». Proceedings of the Institution of Mechanical Engineers, Part D : Journal of Automobile Engineering 203, n^o 3 (juillet 1989) : 185–92. http://dx.doi.org/10.1243/pime_proc_1989_203_165_02.

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This paper describes an investigation into the effects of in-cylinder air motion at the spark plugs on gasoline engine performance. Measurements of combustion angles have been made in a single-cylinder four-stroke disc combustion chamber engine at part load and MBT ignition timing. Seventeen in-cylinder air motion regimes have been produced using masked valves. The air motion in each build has been evaluated by making laser Doppler anemometry (LDA) measurements of mean velocity and turbulence intensity at the spark plug position under motored conditions. It has been shown that there is a strong correlation between turbulence intensity and 10–90 per cent burn angle. It is demonstrated that for this combustion chamber geometry a tumbling air motion is a more effective means of generating turbulence at TDC than swirl.

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Hussein, Hussein J., Steven P. Capp et William K. George. « Velocity measurements in a high-Reynolds-number, momentum-conserving, axisymmetric, turbulent jet ». Journal of Fluid Mechanics 258 (10 janvier 1994) : 31–75. http://dx.doi.org/10.1017/s002211209400323x.

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The turbulent flow resulting from a top-hat jet exhausting into a large room was investigated. The Reynolds number based on exit conditions was approximately 105. Velocity moments to third order were obtained using flying and stationary hot-wire and burst-mode laser-Doppler anemometry (LDA) techniques. The entire room was fully seeded for the LDA measurements. The measurements are shown to satisfy the differential and integral momentum equations for a round jet in an infinite environment.The results differ substantially from those reported by some earlier investigators, both in the level and shape of the profiles. These differences are attributed to the smaller enclosures used in the earlier works and the recirculation within them. Also, the flying hot-wire and burst-mode LDA measurements made here differ from the stationary wire measurements, especially the higher moments and away from the flow centreline. These differences are attributed to the cross-flow and rectification errors on the latter at the high turbulence intensities present in this flow (30% minimum at centreline). The measurements are used, together with recent dissipation measurements, to compute the energy balance for the jet, and an attempt is made to estimate the pressure-velocity and pressure-strain rate correlations.

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Eisele, K., Z. Zhang, M. V. Casey, J. Gu¨lich et A. Schachenmann. « Flow Analysis in a Pump Diffuser—Part 1 : LDA and PTV Measurements of the Unsteady Flow ». Journal of Fluids Engineering 119, n^o 4 (1 décembre 1997) : 968–77. http://dx.doi.org/10.1115/1.2819525.

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This paper describes experimental research aimed at improving our understanding of the complex unsteady three-dimensional flow field associated with the interaction between a pump impeller and its vaned diffuser. The paper provides the results of experiments carried out using Laser Particle Tracking Velocimetry (LPTV) and Laser Doppler Anemometry (LDA), in which time-resolved details of the unsteady flow field in a vaned diffuser of a medium specific speed pump have been obtained as a function of the local position of the pump impeller blades. Detailed flow field measurements have been carried out at several measurement positions in the diffuser and at a number of operating points along the pump characteristic. The measurement results have been analyzed to elucidate some interesting flow features observed in this typical pump diffuser. These include three-dimensional flow at the impeller outlet, flow separation in the diffuser channel, unsteady recirculation of the flow from the diffuser into the impeller, the passage of vorticity in the impeller blade wakes through the diffuser, and periodic unsteadiness and turbulence in the diffuser flow channel. The relevance of these flow features to the stability of the pump characteristic is discussed.

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Chen, Yung Chung, Zhao Cheng Chen, Tung Wu Lu et Chien Ming Chen. « Modulating the Optical Fiber Sensor of Laser Doppler Anemometry for Measuring the Chicken Blood Velocity ». Key Engineering Materials 326-328 (décembre 2006) : 1355–58. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.1355.

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We designed a new module of Laser Doppler Anemometry (LDA) with fiber optical system, which is mainly comprised of a laser diode, optical fibers and a two dimensional (2D) photodetector. The fiber optical system involved a laser diode (VCSEL, Copax Inc.) with 850 nm wavelength, single mode fiber (Prime Optical Fiber Inc.), half coupler and two fiber collimators. The 2D photodetector made by silicon PIN photodiode is aligned between the two collimators with 39° beams cross angle and all the components were set into a rectangle case, which have coin’s size and can be accommodated by two same set of these components. We added anticoagulant and antiseptic into fresh chicken blood and diluted it with normal saline, and then put the diluted blood into a beaker with a motor in the liquid. The diluted blood was pumped by the motor into an aqueduct which is connected to glass aqueduct, and back to the beaker to form a circulation system. In the experiments, we evaluate the relationships among the blood cell velocity and diameter of glass tube, temperature variation of blood, and concentrations of blood. By analyzing the results of these experiments, the main factor that affects the precision of velocity measurement is the cross angle of two injected laser beams and the intensity of scattering light. The module constructed by optical fiber light can precisely measure the velocity of blood flow at most 5% error.

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Muguercia, I., E. Largaespade, W. Li et M. A. Ebadian. « Fluid flow behavior inside a circular helicoidal pipe using a laser doppler anemometry/velocimetry (LDA/LDV) system ». Experimental Thermal and Fluid Science 7, n^o 2 (août 1993) : 149–50. http://dx.doi.org/10.1016/0894-1777(93)90202-t.

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Yan, L., S. Lin et G. H. Vatistas. « REYNOLDS STRESSES IN CONFINED VORTEX FLOWS ». Transactions of the Canadian Society for Mechanical Engineering 23, n^o 2 (juin 1999) : 287–305. http://dx.doi.org/10.1139/tcsme-1999-0020.

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Reynolds stresses in confined vortex flows have been studied analytically and experimentally. Equations for the Reynolds shear stresses are derived based on the kinetic energy equations and experimental observations. The Reynolds shear stresses are obtained by solving the equations analytically. The unknown parameters appearing in the analytical solutions are determined from experimental data. The Reynolds normal stresses are obtained directly from the experiments which are performed by means of Laser Doppler Anemometry (LDA). The effects of the contraction ratio and the inlet Reynolds number on the Reynolds stresses in the vortex flow from the main section to the exit section of the vortex chamber are analyzed. It is found that the contraction ratio affects the behaviour of the Reynolds stresses, and that a higher inlet Reynolds number results in a higher level of the Reynolds stresses.

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Li, Y., S. Liu, S.-X. Shi, M. Feng et X. Sui. « An investigation of in-cylinder tumbling motion in a four-valve spark ignition engine ». Proceedings of the Institution of Mechanical Engineers, Part D : Journal of Automobile Engineering 215, n^o 2 (1 février 2001) : 273–84. http://dx.doi.org/10.1243/0954407011525511.

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The formation and break-up of the tumble in the cylinder were studied in a single-cylinder four-valve spark ignition engine using laser Doppler anemometry (LDA) measurements and multidimensional numerical simulations. The flow structure generated by the tumble break-up was also analysed using the cycle-resolved LDA data processing method. These results show that, during the intake stroke, two counter-rotating vortices are generated in the cylinder by the intake flow along the two sides of the cylinder. They then gradually evolve into the tumble vortex at the initial stage of the compression stroke. Tumble motion can be strengthened by increasing the intake flow going along the surface of the exhaust valves and/or decreasing the intake flow descending directly along the cylinder wall on the side of intake valves. Although a partially decayed tumble vortex still exists in the central part of the combustion chamber near the end of compression, in other parts of the combustion chamber the tumble distorts and breaks up into small vortices and eddies so that the root mean square velocity fluctuation increases. The flow structure generated by the tumble break-up has a characteristic of lower frequency and larger eddy scale.

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Hughes, N. J., et J. F. Carrotte. « Unsteadiness of the Port Feed and Jet Flows Within a Gas Turbine Combustion System ». Journal of Fluids Engineering 126, n^o 1 (1 janvier 2004) : 55–62. http://dx.doi.org/10.1115/1.1637629.

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This paper describes an experimental investigation on a gas turbine combustor geometry that is typical of current aerospace applications. The isothermal investigation has concentrated on the flow approaching and passing through a primary port, and the subsequent jet formed by this flow within the flame tube. It is widely accepted that the jet formed by a port in such a geometry is influenced by the mean approach flow conditions. This paper, though, addresses whether the high levels of turbulence and unsteadiness, as is typically found within the approach flow of these systems, can also affect the time dependent jet and flow field generated by the port. Measurements using both hot wire anemometry (HWA) and a three component Laser Doppler Anemometry (LDA) system were therefore used to characterize the flow field. Cross correlation of simultaneous measurements indicated that velocity fluctuations in the feed annulus correlate with fluctuations inside the port and flame tube. The sign and magnitude of the correlations are presented between various feed annulus, port and flame tube spatial locations. The results suggest the time dependent external flow field can influence the flow field within the flame tube and hence, potentially, flame stability, mixing and emissions.

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Baskaya, S., A. Gilchrist et S. M. Fraser. « Buoyancy-Induced Flow Through a Narrow Chamber Containing an Internal Heat Source : Comparison of Experimental Measurements and Numerical Simulations ». Proceedings of the Institution of Mechanical Engineers, Part C : Journal of Mechanical Engineering Science 210, n^o 5 (septembre 1996) : 489–98. http://dx.doi.org/10.1243/pime_proc_1996_210_222_02.

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Natural convection ventilation of a rectangular chamber containing a heated rectangular body has been investigated both experimentally and computationally. The heated square blockage within the partial enclosure was adjacent to the adiabatic lower surface of the chamber and the three exposed surfaces of the block were such as to give a constant heat flux. The air inlet and outlet were located at the bottom and top of the chamber vertical walls respectively, and were of equal area. Velocity measurements were performed using laser Doppler anemometry (LDA) with a one-component He–Ne laser connected to a burst spectrum analyser (BSA). Detailed velocity profiles were measured at the inlet, outlet and at several locations inside the chamber. Temperatures of the heated air at the outlet were measured with a chromel–alumel (type K) bare wire thermocouple probe. Three-dimensional laminar and turbulent (k–e model) numerical simulations were obtained by solving the governing equations using the computational fluid dynamics (CFD) code PHOENICS. Comparisons of experimental and computational results showed very good agreement in most of the flow field.

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Weclaś, M., A. Melling et F. Durst. « Characteristics of scavenging flow in transfer ports of a motored two-stroke engine ». Proceedings of the Institution of Mechanical Engineers, Part D : Journal of Automobile Engineering 211, n^o 4 (1 avril 1997) : 301–17. http://dx.doi.org/10.1243/0954407971526452.

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A real two-stroke engine [specifically an Orbital Combustion Process X (OCP-X) engine] was optically modified for application of laser Doppler anemometry (LDA) and flow visualization. Two velocity components were measured in two transfer ports of the motored engine. Spatial and temporal distributions of velocity indicated that the scavenge flow was very complex, highly non-uniform across the transfer ports, and strongly time dependent with respect to the port opening and closing periods. Mean velocities averaged over these two periods characterize the scavenge flow in the transfer ports but do not represent the velocity peaks at the port opening and closing, respectively. Effects of the exhaust valve in the exhaust port and of depression applied to the exhaust port on the temporal distribution of scavenge flow in transfer ports were significant only for a high enough pressure difference between the crankcase and the exhaust.

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Keynton, R. S., S. E. Rittgers et M. C. S. Shu. « The Effect of Angle and Flow Rate Upon Hemodynamics in Distal Vascular Graft Anastomoses : An In Vitro Model Study ». Journal of Biomechanical Engineering 113, n^o 4 (1 novembre 1991) : 458–63. http://dx.doi.org/10.1115/1.2895427.

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A steady flow, in vitro model of distal arterial bypass graft junctions was used to examine the effects of junction angle and flow rate on the local velocity field. Three test sections were fabricated from Plexiglas™ tubing having anastomotic junction angles of either 30, 45, or 60 deg. Flow visualization revealed velocity profiles skewed toward the outer wall with a flow split around a clear stagnation point along the outer wall. Laser Doppler anemometry [LDA] measurements confirmed a distinct stagnation point at the outer wall and both reverse and forward shear were detected immediately upstream and downstream, respectively, of this site. Axial velocities and shear rates along the outer wall were higher than along the inner wall and occurred in the junction angle order: 45, 60, and 30 deg. This study clearly identified changes in wall shear which varied with the anastomotic angle and flow rate.

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Kysela, Bohus, Jiří Konfrst, Zdeněk Chára et Ivan Fořt. « Structure of turbulent velocity field in the discharge stream from a standard Rushton turbine impeller ». Chemical Industry and Chemical Engineering Quarterly 23, n^o 2 (2017) : 151–60. http://dx.doi.org/10.2298/ciceq151002025k.

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The radial discharge jet from a standard Rushton turbine was investigated by the Laser Doppler Anemometry (LDA) method. Several distances from the impeller blades (in the radial direction) were chosen for the measurement of axial profiles: all three velocity components (radial, tangential and axial) were measured at each point of the axial profile. The obtained velocity time records were analysed and averaged results were decomposed into three parts: mean ensembleaverage, random and periodic. The ratio of the derived periodic part of the velocity was evaluated in each measurement point and for all velocity components. The obtained results indicate the regions where the periodic part of the velocity has significant effect and where the contribution of this part is almost negligible. Although the values of the periodic part of all velocity components have a rather similar range, the spatial distributions are different in the investigated region.

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Gantar, Marjan, Dusan Florjancic et Brane Sirok. « Hydraulic Axial Thrust in Multistage Pumps—Origins and Solutions ». Journal of Fluids Engineering 124, n^o 2 (28 mai 2002) : 336–41. http://dx.doi.org/10.1115/1.1454110.

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In this paper, axial thrust problems of multistage pumps are presented. The entire investigation has been focused on the pump design concept having all impellers in series (facing in one direction) and is valid for barrel casing type as well as for segmental type. The major part of the investigation has been experimental on one stage testing arrangement, using also Laser Doppler Anemometry (LDA) for determination of fluid rotation in the impeller side chamber. Numerical flow analysis (NFA) has been applied for some flow variants in order to verify whether a numerical approach could simulate the test results. The phenomenon of fluid rotation in side chambers and its effect on impeller hydraulic axial thrust have been determined for different leakage flow regimes. The influence of increased wear ring radial clearance on axial thrust has been analyzed together with the solutions for pump hydraulic axial thrust reduction.

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Plamann, Karsten, Holger Zellmer, Jürgen Czarske et Andreas Tünnermann. « Directional discrimination in laser Doppler anemometry (LDA) without frequency shifting using twinned optical fibres in the receiving optics ». Measurement Science and Technology 9, n^o 11 (1 novembre 1998) : 1840–46. http://dx.doi.org/10.1088/0957-0233/9/11/008.

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Zhang, Zh. « Dual-Measurement-Method and its extension for accurately resolving the secondary flows in LDA (Laser Doppler Anemometry) applications ». Flow Measurement and Instrumentation 16, n^o 1 (mars 2005) : 57–62. http://dx.doi.org/10.1016/j.flowmeasinst.2004.08.001.

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Baldwin, J. T., S. Deutsch, D. B. Geselowitz et J. M. Tarbell. « LDA Measurements of Mean Velocity and Reynolds Stress Fields Within an Artificial Heart Ventricle ». Journal of Biomechanical Engineering 116, n^o 2 (1 mai 1994) : 190–200. http://dx.doi.org/10.1115/1.2895719.

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Laser Doppler Anemometry measurements of mean (ensemble average) velocities and turbulent (Reynolds) stresses at 140 locations within the left ventricle of the Penn State 70 cc electric artificial heart/ventricular assist device are reported at 8 times during the cardiac cycle. Mean velocity patterns indicate that the surfaces of the blood sac and valve tracts are exposed to significant levels of wall shear stress (good wall washing) during some portion of the flow cycle, and there is no location where the flow is stagnant over the entire flow cycle. This implies that thrombus deposition within the artificial heart should be suppressed. Turbulent stresses in the main pumping chamber and the outflow tracts of the tilting disk valves do not exceed 2000 dynes/cm2. The highest turbulent stresses (20,000 dynes/cm2) and smallest turbulent microscales (6 μm) are found in the regurgitant jets on the minor orifice side of the aortic valve during diastole and the mitral valve during systole. Taken together, the data suggest that improvements in artificial heart fluid mechanics will come through valve design and pump operating conditions, not pumping chamber design.

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