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Particle Collisions in a Lumped Particle Model

Communications in Computational Physics 2011年第9期10卷 823-843页

作者： Omar al-Khayat Are Magnus Bruaset Hans Petter Langtangen Computational Geosciences CBCSimula Research LaboratoryP.O.Box 134NO-1325 LysakerNorway Department of Informatics University of OsloP.O.Box 1080BlindernNO-0316 OsloNorway Center for Biomedical Computing Simula Research LaboratoryP.O.Box 134NO-1325 LysakerNorway

This paper presents an extension of the lumped particle model in[1]to include the effects of particle *** lumped particle model is a flexible framework for the modeling of particle laden flows,that takes into account fundamental features,including advection,diffusion and dispersion of the *** this paper,we transform a binary collision model and concepts from kinetic theory into a collision procedure for the lumped particle *** apply this new collision procedure to investigate numerically the role of particle collisions in the hindered settling *** hindered settling effect is characterized by an increase in the effective drag coefficient CD that influences each particle in the *** coefficient is given by CD=(1−φ)−nC∗D,whereφis the volume fraction of particles,C∗D is the drag coefficient for a single particle,and n≃4.67 for creeping *** obtain an approximation for CD/C∗D by calculating the effective work done by collisions,and comparing that to the work done by the drag *** our numerical experiments,we observe a minimal value of n=***,by allowing high energy dissipation,an approximation for the classical value for creeping flow,n=4.7,is *** also obtain high values for n,up to n=6.5,which is consistent with recent physical experiments on the sedimentation of sand grains.

关键词： Lumped particle model particle collision hindered settling

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VELOCITY AND SUSPENSION CONCENTRATION IN SEDIMENT-MIXED FLUID

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International Journal of Sediment Research 2002年第3期17卷 220-232页

作者： B.S.MAZUMDER,K.GHOSHAL Professor Physics and Applied Mathematics Unit Indian statistical Institute Calcutta-700 108 India. Project Fellow Flume Laboratory Physics and Applied Mathematics Unit Indian Statistical Institute Calcutta-700 108 India.

The present paper is focussed on the effects of viscous and turbulent shear stresses on both vertical velocity and concentration distributions in large suspension of sands. When the flow carries large amount of sediments in suspension, the properties of fluid mixture are changed in terms of modified viscosity, density and fall velocity, and hence the flow characteristics. Theoretical models have been developed for both velocity and concentration profiles, taking into account the viscous and turbulent shear stresses, which are the function of volumetric concentration. Comparison of theoretical models with experimental data reveals that (i) the modified velocity and concentration profiles agree well with the observed data for high suspension, (ii) the higher the sediment suspension, the smaller the von-Karman constant, and (iii) sediment diffusion coefficient is less than momentum diffusion coefficient for fine sands in suspension.

关键词： Sediment suspension Viscosity Turbulent shear stress hindered settling Velocity and concentration profiles

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MEASURING TECHNIQUES FOR HIGHLY CONCENTRATED SAND-MUD MIXTURES

MEASURING TECHNIQUES FOR HIGHLY CONCENTRATED SAND-MUD MIXTUR...

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第九次河流泥沙国际学术大会

作者： P.J.T.DANKERS citg.tudelft.nl J.C.WINTERWERP W.G.M.VAN KESTEREN Delft University of Technology Faculty of Civil Engineering and Geosciences Hydraulic engineering section P.O. Box 5048 2600 GA Delft The Netherlands. E-mail: p.i.t.dankers WL Delft Hydraulics The Netherlands Delft University of Technology Faculty of Civil Engineering and Geosciences Environmental Fluid Mechanics Section The Netherlands WL Delft Hydraulics The Netherlands

＜正＞In the past, research on hindered settling mainly focused on sand or mud. In this research an attempt is made to develop a measuring technique to examine the hindered settling of sand-mud mixtures. It was found that a combination of techniques was needed to determine the settling velocities and the concentrations of the sand and mud fraction separately. After reviewing several techniques a combination of a non-intrusive X-ray, an ASTM （acoustic sand transport meter） and a video camera seemed to perform best. The results of the experiments shall at a later stage be used in a numerical simulation in order to test a proposed eauation for the hindered settling of sand-mud mixtures.

关键词： Sand-mud mixtures hindered settling Cohesive sediment Measuring techniques

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