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Analytical study on accelerating falling of non-spherical particle in viscous fluid

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International Journal of Sediment Research 2014年第3期29卷 423-430页

作者： Amir MALVANDI Davood Domairry GANJI Ali MALVANDI Karaj Branch Islamic Azad University Mechanical Engineering Department Babol Noshirvani University of Technology Department of Electrical Biomedical and Mechatronic EngineeringQazvin BranchIslamic Azad University

Unsteady motion of a vertically falling non-spherical particle has attracted considerable attention due to its frequent applications in nature and industry.A series of semi-analytical methods have been used to raise the results’ accuracy as well as widening the region of *** current study pursued a new analytical solution for the unsteady motion of a rigid non-spherical particle in a quiescent Newtonian fluid,based on the Optimal Homotopy Analysis *** a view towards obtaining the highest level of accuracy and ensuring the convergence of the analytical results,the averaged residual errors were obtained and *** addition to flexibility,it was also proven that the proposed method can lead to completely reliable and precisely accurate *** on the series solution,the effects of physical parameters on the terminal settling velocity(*** greatest velocity that a falling body may reach)and the acceleration time(*** time that a particle reaches the settling velocity) are investigated.

关键词： non-spherical particle Unsteady motion Sedimentation Analytical solution Homotopy analysis method

Study on a semi-resolved CFD-DEM method for rod-like particles in a gas-solid fluidized bed

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Particuology 2024年第4期87卷 20-36页

作者： Liping He Zhengxian Liu Yongzhi Zhao Department of Mechanics School of Mechanical EngineeringTianjin UniversityTianjin300350China Insttute of Process quipment College of Energy EngineeringZhejiang UniversityHangzhou30027China

Based on a semi-resolved CFD-DEM coupling method,this study proposed a method that uses the minimum distance between the fluid grid and the particle boundary as a reference value to determine the degree of influence of the target fluid grid on the particle's drag force.A fluidized bed of rod-like particles was chosen as a typical case to investigate the effect of different fluid grid scales on various fluidized bed characteristic *** calculation performance of the semi-resolved and unre-solved CFD-DEM coupling algorithm on key fluidized bed characteristic parameters such as average pressure drop,particle frequency distribution with bed height,and particle orientation distribution were *** was found that the semi-resolved CFD-DEM coupling algorithm gradually obtained results with higher consistency with decreasing fluid grid scale for key parameters such as particle frequency distribution with bed height,particle orientation distribution,and time-history mixing index,exhibiting a phenomenon similar to grid independence in fluid *** comparing with experimental results,it was verified that the semi-resolved CFD-DEM coupling algorithm can be applied to simulate multi-granular gas-solid systems with fluid grid scales equivalent to particle *** algorithm solves the limitation of fluid grid scale in the unresolved CFD-DEM coupling framework and improves the grid adaptability of the CFD-DEM coupling simulation algorithm.

关键词： CFD-DEM Semi-resolved method Fluid-solid flow non-spherical particle Fluidized bed

Alignment of inertialess spheroidal particles in flow-structure-dominated regions of turbulent channel flow:shape effect

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Acta Mechanica Sinica 2024年第8期40卷 45-66页

作者： Zhiwen Cui Lihao Zhao Applied Mechanics Laboratory Department of Engineering MechanicsTsinghua UniversityBeijing100084China Laboratory of Flexible Electronics Technology Tsinghua UniversityBeijing100084China

The alignment of elongated fibers and thin disks is known to be significantly influenced by the presence of fluid coherent structures in near-wall turbulence(Cui et al.2021).However,this earlier study is confined to the spheroids with infinitely large or small aspect ratio,and the shape effect of finite aspect ratio on the alignment is not *** current study investigates the shape-dependent alignment of inertialess spheroids in structure-dominated regions of channel *** utilizing an ensemble-averaged approach for identifying the structure-dominated regions,we analyze the eigensystem of the linear term matrix in the Jeffery equation,which is governed by both particle shape and local fluid velocity *** contrast to earlier conventional analysis based on local vorticity and strain rate,our findings demonstrate that the eigensystem of the Jeffery equation offers a convenient,effective,and universal framework for predicting the alignment behavior of inertialess spheroids in turbulent *** leveraging the eigensystem of the Jeffery equation,we uncover a diverse effect of fluid coherent structures on spheroid alignment with different particle ***,we provide explanations for both shape-independent alignments observed in vortical-core regions and shape-dependent alignments around near-wall streamwise vortices.

关键词： non-spherical particle Direct numerical simulation Wall turbulence particle-laden flow

Performance characteristics of the airlift pump under vertical solid-water-gas flow conditions for conveying centimetric-sized coal particles

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International Journal of Coal Science & Technology 2024年第2期11卷 53-66页

作者： Parviz Enany Carsten Drebenshtedt Faculty of Mining and Special Civil Engineering Technische Universitat BergakademieGustav-Zeuner StraBe 1A09599FreibergGermany

In this study,the installation of an airlift pump with inner diameter of 102 mm and length of 5.64 m was utilized to consider the conveying process of non-spherical coal particles with density of 1340 kg/m3 and graining 25-44.5 *** test results revealed that the magnitude of increase in the solid transport rate due to the changes in the three tested parameters between compressed air velocity,submergence ratio,and feeding coal possibility was not the same,which are stand in range of 20%,75%,and 40%,***,creating the optimal airlift pump performance is highly dependent on submergence *** importantly,we measured the solid volume fraction using the method of one-way valves in order to minimize the disadvantages of conventional devices,such as fast speed camera and conductivity ring *** results confirmed that the volume fraction of the solid phase in the transfer process was always less than 12%.To validate present experimental data,the existing empirical correlations together with the theoretical equations related to the multiphase flow was *** overall agreement between the theory and experimental solid delivery results was particularly good instead of the first stage of conveying *** drawback can be corrected by omitting the role of friction and shear stress at low air income *** was also found that the model developed by Kalenik failed to predict the performance of our airlift operation in terms of the mass flow rate of the coal particles.

关键词： Vertical velocity non-spherical particle Submergence ratio Three-phase flow Churn flow Superficial velocity

NURBS-based DEM for non-spherical particles

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Particuology 2020年第2期18卷 65-76页

作者： Shiwen Liu Feiguo Chen Wei Ge Philippe Ricoux State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesP.O.Box 353Beijing 100190China School of Chemical Engineering University of Chinese Academy of SciencesBeijing 100049China Data Processing and Modeling TOTAL Scientific DivisionFrance

The discrete element method(DEM)is used to analyze complex practical granular systems;however,the representation of real shapes is an important consideration because behavior of non-spherical particles is unlike that of spherical particles both individually and *** this study,we use non-uniform rational basis-splines(NURBS)to describe the shapes of non-spherical particles and introduce a contact detection scheme based on quadratic convergence,to simulate the behaviors of elliptical *** simulation results are compared with those based on polygons,in terms of the shape description and contact treatment,to demonstrate the high accuracy and efficiency of NURBS-based DEM.

关键词： non-spherical particle Discrete element method NURBS Facet-based DEM Granular system

Multi-level DEM study on silo discharge behaviors of non-spherical particles

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Particuology 2023年第11期82卷 179-191页

作者： Lei Xu Xiukai Wu Jingyin Liang Shuai Wang Shiyi Bao Institute of Process Equipment and Control Engineering College of Mechanical EngineeringZhejiang University of TechnologyHangzhou310032China Engineering Research Center of Process Equipment and Remanufacturing Ministry of EducationChina State Key Laboratory of Clean Energy Utilization Zhejiang UniversityHangzhou310027China

The silo discharge of non-spherical particles has been widely practiced in engineering processes, yet the understanding of multi-level mechanisms during solid transportation is still lacking. In this study, a high-fidelity super-ellipsoid Discrete Element Method (DEM) model is established to investigate the discharge behaviors of non-spherical particles with different size distributions. After the comprehensive model validations, we investigated the effects of particle shape (aspect ratio and particle sharpness) on the particle level discharge behaviors. The discharge rates of the ellipsoid particles used in the current work are larger than the spherical particles due to the larger solid fraction. The discharge rates of the cuboid-like particles are determined by the combined effect of the solid fraction and the contact force. Parcel level data show that the translational movements of the ellipsoid particles are more ordered, which is supported by the global level data. Strong correlations exist between the particle level and parcel level data, especially the ellipsoid particles and the large particles in the polydispersed cases.

关键词： Multi-level study non-spherical particle Numerical simulation Silo discharge Granular flow

An extended unresolved CFD-DEM coupling method for simulation of fluid and non-spherical particles

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Particuology 2022年第9期20卷 1-12页

作者： Liping He Zhengxian Liu Yongzhi Zhao Department of Mechanics School of Mechanical EngineeringTianjin UniversityTianjin 300350China Institute of Process Equipment College of Energy EngineeringZhejiang UniversityHangzhou 310027China

This study develops an extended unresolved CFD-DEM coupling method for simulation of the fluid-solid flow with non-spherical *** limitation of fluid grid size is discussed,by simulating the settling of a cylinder in a Newtonian fluid based on the resolved and unresolved CFD-DEM coupling ***,the calculation of porosity and the fluid-particle relative velocity based on the particle shape enlarge-ment method for simulation of non-spherical particles is *** availability of the particle shape enlargement method for the simulation of non-spherical particles with different sphericity is discussed in this work,by comparing it with the results from the equivalent diameter enlargement *** lim-itation of the equivalent diameter enlargement method for non-spherical particles is revealed from the simulation *** typical cases are employed to elaborate and verify the extended unresolved CFD-DEM method based on particle shape enlargement method,by presenting a good consistency with the experimental *** proves that the extended unresolved CFD-DEM method is suitable for differ-ent CFD grid size ratios,and consolidates that it is a universal calculation method for CFD-DEM coupling simulation.

关键词： CFD-DEM Unresolved method Fluid-solid flow non-spherical particle Rod

Effect of non-spherical particles on burning behavior during aluminum combustion

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Particuology 2020年第4期18卷 173-183页

作者： Jinyun Wang Zailin Yang Mengjun Wang College of Aerospace and Civil Engineering Harbin Engineering UniversityHarbin 150001China Key Laboratory of Dual Dielectric Power Technology Hebei Hanguang Industry Co.Ltd.Handan 056017China

The shape of an aluminum particle is assumed to be spherical or an equivalent sphere during the combustion *** an assumption lacks objectivity and leads to unreasonable approximations of burning efficiency and *** investigate the influence of non-spherical particles on burning behavior,this study focused on a theoretical and experimental investigation of the combustion of nanoscale aluminum ellipsoidal *** for prolate and oblate spheroids in aluminum combustion were established to explore combustion properties such as mass release rate,linear burning rate,burning rate,and burnout *** validate the theoretical results,combustion experiments were conducted on three *** agreement between the results of numerical simulation and experimental findings was obtained in terms of the particle burning *** was found that particle morphology(such as prolate or oblate spheroid shape)and size play a significant role in the combustion performance of nanosized aluminum particles.

关键词： Nanosized aluminum Combustion non-spherical particle Morphology

DEM investigation on conveying of non-spherical particles in a screw conveyor

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Particuology 2022年第6期20卷 17-31页

作者： Hongyuan Sun Huaqing Ma Yongzhi Zhao Institute of Process Equipment College of Energy EngineeringZhejiang UniversityHangzhou 310027China

Screw conveyors are extensively used in modern industry such as metallurgy,architecture and pharmaceutical due to their high-efficiency in the transportation of granular *** substantial efforts have been devoted to the study of the screw *** method is an effective way to study screw ***,previous studies have mainly focused in the regime of spherical particles while the in-depth investigations for non-spherical particles that should be the most encountered in practical applications are still *** view of the above situations,discrete element method(DEM),which has been widely accepted in simulating the discrete systems,is utilized to investigate the conveying process of non-spherical particles in a horizontal screw conveyor,with particles being modeled by *** addition,a wear model called SIEM(Shear Impact Energy Model)is incorporated into DEM to predict the wear of screw *** DEM simulation results demonstrate that the particle shape is influential for the flow behaviors of particles and the wear of *** conveying performance evaluated quantitatively of both mass flow rate and power consumption is subsequently obtained to investigate the effect of sphericity of particle with different operation ***,particle collision frequency and collision energy consumption are acquired to investigate the possible particle breakage between particles and screw *** comparisons between particle-particle collision and particle-wall collision reveal that particles with large shape index have more possibility to be damaged in particle-wall impingement.

关键词： DEM Screw conveyor Super-ellipsoid particle non-spherical particle Wear