bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Origin of Turbulence Acquired by Heavy Particles in a round, turbulent jet
Authors: Mastorakos Epaminondas , McGuirk James J. , Taylor Alexander M. K. P. 
Published: December 2004

AbstractThe paper describes the application of a stochastic separated flow model for the dispersed phase to the prediction of a particle‐laden turbulent air jet discharging at 13 m/s from a 15 mm nozzle into stagnant surroundings. Emphasis is placed on the stochastic element of the Lagrangian particle tracking part of the model and on the importance of particle initial conditions over the first 20 jet diameters. Calculations are presented for 80 m̈m sized glass particles which clarify how particles with turbulent Stokes number less than unity acquire axial turbulence much larger than radial. Far from being only a response to the gas‐phase turbulence as implied by the model, the axial turbulence is shown to be also produced by an interaction between particle radial turbulence fluctuations and cross‐stream spatial gradients in particle mean velocity, here referred to as "fanspreading". In addition, initial particle turbulence levels remain identifiable for about 10 jet diameters; the initial radial turbulence reinforces the fan‐spreading contribution and leads to extra generation of axial turbulence farther downstream. In general, the results agree well with experimental measurements.
On‐Line Characterization of the Shape and Size of Particles
Authors: Castellini Carlo , Francini Franco , Longobardi Giuseppe , Pampaloni Enrico 
Published: December 2004

AbstractAn image analysis system for extracting on‐line quantitative geometric and densitometric information from images of ore samples is described. The apparatus employs a pulsed semiconductor laser as the light source for illuminating of a flowing stream of particles and a non‐interlaced solid‐state TV camera as size measurement device in a shadowgraph imaging system. The problem of the sampling volume is discussed and several size distributions of solid particulates are presented. The particle size measurement range is 2–400 μm.
Fly Ash Size Distributions: Use of coulter multisizer and fitting to truncated lognormal distributions
Authors: Ghosal Sarbajit , Ebert Jon L. , Self Sidney A. 
Published: December 2004

AbstractAccurate information on the size distribution of fly ash is needed to determine its role in the radiation transfer process in pulverized coal combustors. The Coulter Multisizer was used to determine the size distribution in the particle diameter range 1–200 μm. To size over such large diameter ranges, data must be obtained using several orifices, and then combined. In order to use the smaller orifices, the larger particles have to be removed from the sample. A wet‐sieving apparatus, designed for accurate separation of the particles by size, is described. A scheme for combining data obtained using orifices of different diameters is presented. It appears from this study that the lower limit of size measurement using an orifice is set by sensitivity, rather than by signal/noise. A lognormal distribution function, truncated outside the measurement limits, fits the size distribution data well. This function allows detailed size information to be stored compactly using four parameters. Size parameters for six fly ashes representative of U. S. coals are presented.
The Angular Polarization Ratio for the Characterization of Small Droplets in Oil Sprays
Authors: Ossler Frederik , Beretta Federico , D'Alessio Antonio , Tregrossi Antonio 
Published: December 2004

AbstractThe angular patterns of the polarization ratio were calculated for droplets with diameters between 0.020 and 50 μm at 500 nm wavelength. It was observed that the patterns for droplets slightly smaller than 1 μm were dominated by a backward peak belonging to the glory. The peak was successfully used to characterize aerosols of light and heavy oils with a Junge‐like size distribution. Experiments conducted with heavy oil sprays produced by air‐assisted atomization presented the same feature. A quantitative comparison of the experimental results with the Lorenz‐Mie theory showed that the size distribution of these sprays was bimodal.
Sampling of Autocorrelating Powder Flows
Authors: Heiskanen Kari , Niemelä Oili 
Published: December 2004

AbstractSampling powder flows in industrial grinding circuits are discussed. Work was done with different types of sampler and with different minerals and sampling objectives. It was found that all the samplers showed marked autocorrelation in sample mass for all the minerals ground. Typical autocorrelation could be found at both high (1 · 10−3–15 · 10−3 Hz) and low (1 · 10−4 – 4 · 10−4 Hz) frequencies. Higher frequencies were attributed to powder transport and low frequencies to mill circuit variations. The effects of the found autocorrelation on systematic errors and on industrial sampling schemes are discussed. Systematic sampling produced large errors if operated at sampling intervals that were high‐frequency autocorrelation frequencies or small multiples of these. Low‐frequency autocorrelation was less detrimental to the sampling results.
Flow Characteristics of Granular Bulk Materials
Authors: Luong Minh Phong 
Published: December 2004

AbstractThe paper discusses the interest in conventional triaxial tests widely used in soil mechanics for a better understanding of both the mechanical behaviour and flow characteristics of granular bulk materials. It proposes a rheological characterization of granular foodstuffs on diverse types of stress path using a conventional triaxial cell. The characteristic state concept, defining the disaggregation threshold of the granular structure, is found to be suitable and even indispensible for examining the mechanical behaviour and the flowability of stored bulk materials. The experimental results readily suggest, as an indicator of the arching effect, a rheological index that characterizes the particle interlocking breakdown and hence the flowability of the stored materials. In addition, this study offers a realistic physical meaning for parameters in use in constitutive models (yield conditions and flow rules) when describing granular flow in various hopper geometries. The case of silos equipped with vibrating hoppers necessitates additionally the study of the rheological behaviour of materials under cyclic and vibratory loadings in order to analyse the processes of densification or disaggregation conditioning the flowability of the stored materials during emptying operations.
Particle‐Induced Limits of Accuracy in Laser Doppler Anemometry
Authors: Ruck Bodo , Pavlovski Boris 
Published: December 2004

AbstractLaser Doppler anemometry (LDA) is one of the most advanced optical measuring techniques for flow velocities and is widely used in industrial and academic laboratories. Based on numerous applications in the past, there is no doubt that LDA is one of the most accurate flow measuring techniques. However, recent investigations have shown that the period lengths of LDA signal bursts are not as constant as one might expect within the individual burst. This can induce an additional scatter in the signal frequency and in the determination of flow velocity from individual bursts. This paper describes experimental investigations which show qualitatively and quantitatively that the particle passage through the laser beams shortly before the point of intersection, i. e. the LDA measuring volume, yields a distorted LDA fringe pattern. The latter results in a scatter of the measured velocity data for those particles passing the center of the measuring volume at the same time.
Generalized Theory for the Simultaneous Measurement of Particle Size and Velocity using laser doppler and laser two‐focus methods
Authors: Albrecht Heinz‐E. , Borys Michael , Hübner Klaus 
Published: December 2004

AbstractEssentially the laser two‐focus (L2F) and laser Doppler anemometer (LDA) are time‐of‐flight anemometers. The velocity of particles in the micrometre range is determined within the limits of an optically fixed measurement distance. For this only one optoelectronic receiver for the detection of the scattered light is required [1, 2]. With an arrangement of two receiving optics, positioned under an off‐axis angle φ and an elevation angle ± ψ to the optical axis of the measurement system, a resolution of three‐dimensional structures can be achieved and with regard to spherical particles it is possible to determine the dimensions by means of the temporal or phase shift of the signals in the receiving optics. A particle size‐dependent distance inside the measurement volume can be fixed, which has to be passed in order to change the signal from one receiving optics to the other. An LDA with an arrangement of two receiving optics for particle sizing is known as a phase Doppler anemometer (PDA); an L2F designed with two receiving optics can be termed a pulse‐displacement two‐focus anemometer (P2F). The physical analysis of the two methods with respect to a temporal signal displacement in the receivers yielded new results.
Particle Mass Loading Effect on a Two‐Phase Turbulent Downward Jet Flow
Authors: Jou Biing‐Hwang , Sheen Horn‐Jiunn , Lee Yuh‐Tzyh 
Published: December 2004

AbstractThe particle mass loading effect on the flow structure of a two‐phase turbulent jet flow was studied. A particle mass loading ratio ranging from 0 to 3.6 was used as the control parameter. The polystyrene solid particles used had nominal diameters of 210 and 780 μm. The flow Reynolds number, which was based on the pipe nozzle diameter and the fluid‐phase centerline mean velocity, was 2 × 104 in the current test. A two‐color laser Doppler anemometer (LDA), combined with the amplitude discrimination method and the velocity filter method, was employed to measure the mean velocity distributions for the particle and fluid phases, and the turbulent intensities and Reynolds stresses of the flow. The two‐phase jet flow field was measured from the initial pipe exit to 90 D downstream. Another one‐component HeNe laser LDA system was also applied to obtain the energy spectra and temporal correlations of the two‐phase jet flow.
Light Scattering by Anthophyllite‐Crocidolite Asbestos Fibers. Part II: Comparison of various approximate theories with the EBCM theory
Authors: Lapalme René , Patitsas Tom A. J. 
Published: December 2004

AbstractThe effect of the geometry of the fiber ends on the scattered intensities is considered. A new modification of the Rayleighdebye‐Gans (RDG) approximate theory, the Mie Substitution Theory (MST) theory, is introduced. The Boundary Value Method (BVM) for the infinite cylinder, the RDG theory, the Shifrin (SFR) modification of the RDG theory and the MST theory are compared with the EBCM theory for various values of fiber diameter, length, refractive index and for various fiber orientations, including random orientation. Scattering from suspensions of fibers, typical of UICC crocidolite and anthophyllite asbestos fibers, is considered using the BVM, the MST and the RDG theories when the fibers are assumed to be aligned and the MST and the RDG theories when the fibers are assumed to be randomly oriented.
Comparison of Dry Test Sieving on Woven Wire Cloths versus electroformed sheets
Authors: Besancon Pierre , Chastang Jean , Lafaye Albert 
Published: December 2004

AbstractDry test sieving results given by woven wire cloths with a square mesh and by round electroformed apertures were compared using sands of various origin. The difference has been found to be constant and independent of substance and quantile. The quantile obtained on a square mesh was converted into the corresponding quantile on an electroformed sheet of the same nominal aperture by multiplication by a constant factor of 1.21 ± 0.04.
The Use of Laser Backscatter Instrumentation for the on‐line measurement of the particle size distribution of emulsions
Authors: Sparks Ronald G. , Dobbs Charles L. 
Published: December 2004

AbstractThe response of the Partec laser backscatter particle size analyzer has been tested under a variety of conditions. Various materials posessing different light scattering characteristics have been examined and the response of the Partec instrument has been evaluated. In particular the system response to transparent particle systems (e.g. oil in water emulsions) tas been studied. It has been found that the Partec laser backscatter instrument provides reasonably accurate and reproducible results when used to characterize opaque, highly reflective particles such as hydrated alumina, but suffers from a lack of sensitivity to fine transparent particles such as oil droplets. The instrument does, however, readily detect the presence of opaque particle contaminants in oil‐water emulsions.
Size and Velocity Measurements of Large Drops in Air and in a liquid‐liquid two‐phase flow by the phase‐Doppler technique
Authors: Haugen Per , Hayes Edward I. , von Benzon Hans‐Henrik 
Published: December 2004

AbstractParticles comparable in size to or larger than the measurement volume need extra consideration when measured by a phase‐Doppler system. The phase of the Doppler burst received when such particles traverse the measurement volume depends not only on the size of the particle but also on its trajectory, since the particle is not uniformly illuminated. This paper presents a strategy for securing correct measurements even under such conditions, taking advantage of the three‐detector receiving optics of the Dantec Particle Dynamics Analyzer. The effectiveness of the approach is demonstrated for sizing drops in liquid‐gas and liquid‐liquid two‐phase flows: water drops in air, water drops in FC72 and FC72 drops in water. The combination of water and FC72 is also of interest because the relative refractive index is close to unity. Measurements of drops size were made on a monodisperse stream of drops about 2 mm in diameter, i.e. substantially larger than the measurement volume, and polydisperse distributions of drops ranging in diameter from below 0.2 mm to about 1 mm.
Performance Evaluation of Different Phase‐Doppler Systems
Authors: Domnick Joachim , Dorfner Vitus , Durst Franz , Yamashita Masami 
Published: December 2004

AbstractThe results of comparative measurements of three different phase‐Doppler systems applied to a steady‐state water spray are discussed. The three receiving systems, i. e. DANTEC 57X receiving optics with covariance processor, an AEROMETRICS fibre‐based receiver with DSA processor and standard INVENT phase‐Doppler extension, were used with a 2‐D fibre‐optics‐based transmitting system. A constant scattering angle of 70° was chosen, which is near the Brewster angle for water. Measurements were taken in the spray cone of hollow‐cone pressure atomizer at two different axial distances from the nozzle. Local size distributions, size/velocity correlations and the mean diameters D10 and D32 were compared. The results indicate very good agreement between the different systems, especially with respect to the mean diameters. Larger scatter of the results occurs for the measured volume flow rates, but the calculated mean volume flow rates coincide fairly well with the nominal flow rate of the atomizer.
Optimum Seeding Particles for Successful Laser Doppler Velocimeter Measurements
Authors: Ikeda Yuji , Nishigaki Masashi , Ippommatsu Masamichi , Nakajima Tsuyoshi 
Published: December 2004

AbstractSeeding particles for laser Doppler velocimeter (LDV) measurement have been developed which are of uniform diameter, spherical shape, low loose weight and high melting temperature. Evaluation test results show that the use of the particles can increase the signal quality substantially and extend the measurable field of the LDV, which can hardly be accessed by conventional measurement methods.
Determination of Particle Size Distribution by the analysis of intensity‐constrained multi‐angle photon correlation spectroscopic data
Authors: Wu Chi , Unterforsthuber Klaus , Lilge Dieter , Lüddecke Erik , Horn Dieter 
Published: December 2004

AbstractLaser light scattering (LLS), especially dynamic laser light scattering (DLS), also known as photon correlation spectroscopy (PCS), is a well established method for particle size distribution analysis. It usually involves a Laplace inversion of the field autocorrelation function. However, the resolution is limited because of the ill‐conditioned nature of this Laplace inversion. No unique solution exists when noise is present on the data. In contrast with this ill‐conditioned nature, the angular dependence of scattered (static) intensities is precisely not ill‐conditioned, which allows the resolution of the ill‐conditioned inversion of DLS data to be improved. In order to characterize samples with more complicated size distributions, an intensityconstrained multi‐angle PCS data analysis program has been developed, which is an alternative way of normalizing the field correlation function to that reported by Cummins and Staples [12]. In this program, the field autocorrelation function is normalized to the scattering intensity by using a predetermined coherent factor at each angle, which provides an additional constraint on the Laplace inversion of multi‐angle PCS data analysis. The alternative analysis improves the resolution of PCS and provides a more reliable particle size distribution than single‐angle data analysis. Both simulated and measured LLS data are used to illustrate its application, resolution and limitations.
Optical Multiple Scattering by Particles
Authors: Ishimaru Akira 
Published: December 2004

AbstractWhen an optical beam is incident on particles that are randomly distributed, and if the fractional volume is small, single scattering theory is adequate to explain the scattering characteristics of the medium. However, when the fractional volume is increased, multiple scattering effects cannot be ignored. This paper reviews the fundamental theories of multiple scattering including radiative transfer and diffusion theories. Also included are recent studies on polarization effects, localization, enhanced backscattering, resonant localization, pulse scattering and scattering in dense media.
New Computational Techniques to Simulate Light Scattering from Arbitrary Particles
Authors: Hoekstra Alfons G. , Sloot Peter M. A. 
Published: December 2004

AbstractThe coupled dipole method, as originally formulated by Purcell and Pennypacker [3], is a very powerful method to simulate the elastic light scattering from arbitrary particles. This method, however, has one major drawback: if the size of the particles grows, or if scattering from an ensemble of randomly oriented particles has to be simulated, the computational demands of the coupled dipole method soon become too high. This paper presents two new computational techniques to resolve this problem. First the coupled dipole method was implemented on a massively parallel computer. The parallel efficiency can be very close to 1, implying that the attained computational speed scales perfectly with the number of processors. Second, it is proposed to reduce the computational complexity of the coupled dipole method by including ideas from the so‐called fast multipole methods (hierarchical algorithms) into the coupled dipole method. In this way calculation time can be decreased by orders of magnitude.
Extinction of Radiations in Sterically Interacting Systems of Monodisperse Spheres. Part 1: Theory
Authors: Riebel Ulrich , Kräte Udo 
Published: December 2004

AbstractSo far, the evaluation of extinction measurements has mostly relied on Bouguer‐Lambert‐Beer's law (BLBL), even though BLBL is known to be valid in the limit of low concentrations only. With higher particle concentrations, particle‐particle interactions such as multiple scattering, dependent scattering and steric interactions can lead to important deviations from BLBL. In a discussion of the various interaction mechanisms, steric interactions are shown to be dominating in a wide and practically important range of parameters. For the theoretical description of steric interactions, different complementary models are introduced, including a statistical model, a layer model and a numerical simulation model. The various approaches coincide to yield a simple extinction equation in two versions, applying to the regimes of Fraunhofer diffraction and straight ray propagation, respectively. In any case, BLBL is found as the low concentration limit of the extinction equation. All considerations are restricted, so far, to the case of monodisperse spherical particles.
Diffraction Patterns of Static Particles on a 2‐D Surface
Authors: Cao Jing , Watson David 
Published: December 2004

AbstractThe diffraction patterns of static particles deviate from those of dynamic particles of the same distribution characteristics. Use of diffraction solutions based on independent scattering to analyse such diffraction patterns leads to a narrower size distribution biased towards the smaller sizes. A 2‐D coherent diffraction model using an inter‐particle relation PDF function is developed. The model clearly demonstrates the terms due to the individual particle diffraction and the terms contributed by the inter‐particle correlation, i.e. the coherent effects. The deviation of the static particle diffraction pattern from that of the dynamic particles can be well predicted. The results of this study provide a general solution for utilizing the forward diffraction technique in static particle measurement. One of the important applications of the new model is in the development of a diffraction reference reticle used for diffraction‐based particle sizing instruments verification.
Characterization of Particulate Mixtures by In‐Line Measurments
Authors: Weinekötter Ralf , Reh Lothar 
Published: December 2004

AbstractThe quality of particulate mixtures influences strongly the efficiency of downstream process steps. The design or optimization of mixing processes requires fast and accurate methods for determining mixture quality. This paper describes an optical method for the in‐line concentration measurement of the key (tracer) component in particulate mixtures with fiber optical probes. Small fluctuations of tracer concentration equivalent to a low concentration variance represent a high degree of mixing. Monochromatic light penetrates via fiber optical probes into a powder sample. A photometer measures the intensity of the diffuse reflected light. If the tracer differs in colour from the other components of the mixture its concentration can be determined. Three types of fiber optical probes were tested. For calibration two series of mixed samples covering a broad concentration range were prepared, one consisting of white Al(OH)3 and dark SiC and the other of Al(OH)3 and a much finer green pigment. The calibration graphs are described by the Kubelka‐Munk theory. The influence of changes in particle size on the signals is reduced by choosing a probe with an angled arrangement of the fibers. The sample mass of the probes is estimated to ca. 0.01 g, based on comparison with random mixtures at different tracer concentrations. In‐line measurements provide extensive data sets which allow advanced statistical intepretations of mixing processes.