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Particle Properties (particle + property)
Selected AbstractsA spectral projection method for the analysis of autocorrelation functions and projection errors in discrete particle simulationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 7 2008André Kaufmann Abstract Discrete particle simulation is a well-established tool for the simulation of particles and droplets suspended in turbulent flows of academic and industrial applications. The study of some properties such as the preferential concentration of inertial particles in regions of high shear and low vorticity requires the computation of autocorrelation functions. This can be a tedious task as the discrete point particles need to be projected in some manner to obtain the continuous autocorrelation functions. Projection of particle properties on to a computational grid, for instance, the grid of the carrier phase, is furthermore an issue when quantities such as particle concentrations are to be computed or source terms between the carrier phase and the particles are exchanged. The errors committed by commonly used projection methods are often unknown and are difficult to analyse. Grid and sampling size limit the possibilities in terms of precision per computational cost. Here, we present a spectral projection method that is not affected by sampling issues and addresses all of the above issues. The technique is only limited by computational resources and is easy to parallelize. The only visible drawback is the limitation to simple geometries and therefore limited to academic applications. The spectral projection method consists of a discrete Fourier-transform of the particle locations. The Fourier-transformed particle number density and momentum fields can then be used to compute the autocorrelation functions and the continuous physical space fields for the evaluation of the projection methods error. The number of Fourier components used to discretize the projector kernel can be chosen such that the corresponding characteristic length scale is as small as needed. This allows to study the phenomena of particle motion, for example, in a region of preferential concentration that may be smaller than the cell size of the carrier phase grid. The precision of the spectral projection method depends, therefore, only on the number of Fourier modes considered. Copyright © 2008 John Wiley & Sons, Ltd. [source] Influence of Plasma Spray Parameters on Formation and Morphology of ZrO2,8 wt% Y2O3 DepositsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2001Ahmet Kucuk Spray prints of thermal spray coatings were created on glass slides for air-plasma-sprayed 8-wt%-yttria-partially-stabilized zirconia (YSZ) deposits. The spray parameters such as carrier gas flow rate, standoff distance, and torch power were systematically changed to investigate the influence of these parameters on the YSZ deposit characteristics. The deposit properties such as deposition efficiency (DE), substrate coverage, deposit thickness, and roughness were measured. The deposits sprayed with a 3.5,4.0 L/min carrier gas flow rate at an 80 mm standoff distance exhibited higher values of DE within the range of studied process parameters. The DE increased as much as 25% by varying the carrier gas flow rate from 2.0 to 4.0 L/min. The deposits sprayed at a higher standoff distance and low torch power gave poor deposit characteristics. The deposit characteristics were compared with the in-flight particle parameters and revealed that the deposit characteristics strongly depended on the in-flight particle temperature. Using the in-flight particle properties, the flattening ratio and the splat thickness were calculated. The average size of particles adhering to the substrate was found to drastically change with a change of process conditions, being much less than the average size of the starting powder. [source] An Experimental Study on the Free-Radical Copolymerization Kinetics with Crosslinking of Styrene and Divinylbenzene in Supercritical Carbon DioxideMACROMOLECULAR REACTION ENGINEERING, Issue 1 2009Pedro R. García-Morán Abstract A study on the effect of process conditions and composition of the reacting mixture on the kinetics and particle properties in the copolymerization of styrene and divinylbenzene in supercritical carbon dioxide is presented. Polystyrene -block- polydimethylsiloxane and Krytox 257 FSL (Dupont) were used as stabilizers, and their performance compared. A 38 mL, high-pressure view cell, equipped with one frontal and two lateral sapphire windows, was used as the reacting vessel. The polymer product was characterized for total monomer conversion, gel content, molecular weight averages of the sol fraction and particle size distribution. Acceptable polymerization rates and partially-agglomerated spherical particles were produced under the conditions tested. [source] Gedanken zur Zukunft der FeststoffverfahrenstechnikCHEMIE-INGENIEUR-TECHNIK (CIT), Issue 12 2002H.J. Feise Dr. Abstract Die chemische Industrie erlebt derzeit große Veränderungen. Für die Zukunft erwarten die im ,Solids Processing Industrial Network" beteiligten Experten, dass sich zwei verschiedene Arten von chemischen Anlagen entwickeln: einerseits die vielseitige, modularisierte Mehrzweckanlage und andererseits ,World scale"-Großanlagen. Gleichzeitig wird der bereits hohe Anteil von Feststoffen unter den Produkten der chemischen Industrie weiter steigen und neue Anforderungen stellen: Die Kleinmengenprodukte müssen individuell auf die Bedürfnisse des jeweiligen Kunden zugeschnitten werden, wodurch Product Design zu einer den Wettbewerb bestimmenden Technologie wird. Bei Großanlagen müssen neue Technologien entwickelt werden, welche die notwendigen, hohen Durchsätze bereitstellen und außerdem vom Labor- auf World scale-Maßstab hochskaliert werden können. Einen erheblichen Anteil am künftigen Erfolg wird die Automatisierung haben, deren Einsatz zum Großteil von der Verfügbarkeit geeigneter Inline-Messsysteme und der Entwicklung von Modellen zur Simulation des Prozesses und der dazugehörigen Partikeleigenschaften abhängen wird. On the Future of Solid Processing Techniques The chemical industry is experiencing major changes. The experts of the "Solids Processing Industrial Network" expect that in the future two kinds of chemical plants will develop: on the one hand the polyvalent, multipurpose, modular plant and on the other hand the world-scale plants. At the same time the high percentage of solids as products of chemical processes will continue to increase and therefore new challenges have to be met. Small-scale production of solids has to be customized to the individual customer needs, which means that product design will be a technology that defines the competitiveness. For large plants techniques have to be developed that enable large volumes to be produced but that also allow the reliable scale-up from laboratory scale to world-scale production. Automatization will play a crucial role in the success of solids processing, which will depend on the availability of on-line measurement systems and the development of simulation models for the processes and the particle properties involved. [source] Smoothed Particle Magnetohydrodynamics , III.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2005Multidimensional tests, ·B= 0 constraint ABSTRACT In two previous papers (Papers I and II), we have described an algorithm for solving the equations of Magnetohydrodynamics (MHD) using the Smoothed Particle Hydrodynamics (SPH) method. The algorithm uses dissipative terms in order to capture shocks and has been tested on a wide range of one-dimensional problems in both adiabatic and isothermal MHD. In this paper, we investigate multidimensional aspects of the algorithm, refining many of the aspects considered in Papers I and II and paying particular attention to the code's ability to maintain the ,·B= 0 constraint associated with the magnetic field. In particular, we implement a hyperbolic divergence cleaning method recently proposed by Dedner et al. in combination with the consistent formulation of the MHD equations in the presence of non-zero magnetic divergence derived in Papers I and II. Various projection methods for maintaining the divergence-free condition are also examined. Finally, the algorithm is tested against a wide range of multidimensional problems used to test recent grid-based MHD codes. A particular finding of these tests is that in Smoothed Particle Magnetohydrodynamics (SPMHD), the magnitude of the divergence error is dependent on the number of neighbours used to calculate a particle's properties and only weakly dependent on the total number of particles. Whilst many improvements could still be made to the algorithm, our results suggest that the method is ripe for application to problems of current theoretical interest, such as that of star formation. [source] | ||||||||||