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Generalized algorithms for particle motion and collision with streambeds

International Journal of Sediment Research 2019年第4期34卷 295-306页

作者： Patricio A.Moreno-Casas Fabián A.Bombardelli Juan Pablo Toro Department of Civil and Environmental Engineering University of CaliforniaDavis Facultad de Ingeniería y Ciencias Aplicadas Universidad de los AndesMonse?or Alvaro del Portillo Department of Civil Engineering Universidad Andres Bello

Recent theoretical and numerical models for the motion of saltating particles close to stream beds are constituted of three sub-models: a) a set of equations describing the particle "free flight", b) a sub-model to calculate the post-collision particle velocity, and c) a mathematical representation of the bed roughness. In this paper, a comprehensive three-dimensional(3-D), theoretical/numerical model for bedload motion at large Reynolds numbers is presented. By using geometric considerations and stochastic parameters to characterize collisions with the wall, five new sub-models for representation of bed roughness are, for the first time to the best of our knowledge, proposed and implemented. The emphasis of this paper is on the particle model, for which Basset, Magnus, drag, submerged weight, virtual mass,and lift forces are included. For the range of particle sizes(sands) analyzed herein, it is found that the stream-wise contribution of the Basset force, compared to other forces, may be as large as 60%. Whereas in the wall-normal direction, the Basset force is equally important as the drag force, and it is exceeded only by the submerged weight. It is also found that the best agreement between numerical and experimental results in terms of jump length, jump height, and stream-wise particle velocity is achieved for restitution and friction coefficients of 0.65 and 0.1, respectively. Important conclusions are obtained regarding the lack of realistic prediction with available "roughness" models with small ranges of angles.

关键词： particle saltation particle collision particle rotation Bed-load transport Basset force

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particle collisions in a Lumped particle Model

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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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Charging Properties and particle Dynamics of Chang’e-5 Lunar Sample in an External Electric Field

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Engineering 2024年第11期42卷 267-277页

作者： Junping Gu Xiaoyu Qian Yiwei Liu Qinggong Wang Yiyang Zhang Xuan Ruan Xiangjin Deng Yaowen Lu Jian Song Hui Zhang Yunning Dong Mengmeng Wei Wei Yao Shuiqing Li Weihua Wang Zhigang Zou Mengfei Yang Qian Xuesen Laboratory of Space Technology China Academy of Space TechnologyBeijing 100094China Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education Institute of Nuclear and New Energy TechnologyTsinghua UniversityBeijing 100084China Beijing Institute of Spacecraft System Engineering Beijing 100094China Beijing Orient Institute of Measurement and Test Beijing 100086China Institute of Physics Chinese Academy of SciencesBeijing 100190China College of Engineering and Applied Sciences Nanjing UniversityNanjing 210093China China Academy of Space Technology Beijing 100094China

Facing the challenges of in-situ utilization of lunar regolith resources,applying an external electric field to manipulate lunar particles has become a promising method for space particle control,which mainly depends on the particle charging properties in the applied electric *** the surficial lunar regolith samples brought back from the Moon by the Chang’e-5 mission(CE5 LS),this work successively studied their charging properties,particle dynamics,and their collision damages to aerospace materials under the action of an external electric field in high-vacuum *** results indicated that the charging pro-cess and electrostatic projection of lunar regolith particles under high-vacuum conditions were different from those under atmosphere *** particle diameter range of CE5 LS used in the experiment is 27.7-139.0 *** electric field strength of 3-12 kV·cm^(-1),the charge obtained by CE5 LS is 4.8×10^(-15)-4.7×10^(-13) C and the charge-to-mass ratio is 1.2×10^(-5)-6.8×10^(-4) C·kg^(-1).The CE5 LS is easier to be negatively charged in an external electric ***,significant damages were observed on the target impact surfaces,indicating severe influences of lunar regolith particles on aerospace *** work contributes to a more comprehensive understanding of physical mechanisms controlling the lunar regolith shielding and utilization,and will inspire broad efforts to develop the lunar in-situ engi-neering solutions.

关键词： Chang’e-5 lunar regolith sample Charging properties External electric field particle dynamics particle collision

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Influence and optimization of swirler parameters on elbow wear of deep coal fluidization pipeline transportation system

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Friction 2024年第7期12卷 1408-1433页

作者： Shaodi ZHAO Jiusheng BAO Shirong GE Zhongbin WANG Yan YIN Congguang HUANG School of Mechanical and Electrical Engineering China University of Mining and TechnologyXuzhou 221116China School of Mechanical Electronic and Information Engineering China University of Mining and Technology-BeijingBeijing 100083China Frontier Scientific Research Center for Fluided Mining of Deep Underground Resources China University of Mining and TechnologyXuzhou 221008China

Elbow wear is a major threat to the multiphase pipeline transportation industry,which has a negative impact on the stable operation of the transportation *** order to find the wear reduction methods of elbows in the fluidization pipeline transportation system for 2000-meter-deep coal resources,the swirler was installed upstream of the elbows,and wear simulations and tests of three kinds of elbows were carried *** results showed that the maximum wear rate(MWR)of elbows increased and then decreased along the elbow *** to the different directions of gravity,the heavy wear position(HWP)of the horizontal-vertical(H-V)elbow was in front of the vertical-horizontal(V-H)*** the downstream portion of the horizontal-horizontal(H-H)elbow was still a horizontal pipe,the HWP of the H-H elbow almost covered the whole *** swirler placed upstream of the elbows could make the particles at the elbow move to the intrados of the elbows,resulting in less collision between the particles and the extrados of the elbows,thus reducing the wear of the *** wear reduction effects of swirlers on three different elbows were favorably connected with the guide vane angle(GVA)and negatively correlated with the guide vane length(GVL),decreased first and then increased as the guide vane height(GVH)increased,and were little affected by the guide vane number(GVN)and the guide vane thickness(GVT).The mathematical models between the MWR of the elbows and guide vane parameters were *** bench tests,the wear reduction effect of three kinds of elbows under the optimal guide vane parameters was 58.4%,76.9%,and 78.6%,*** errors between the bench test results and the simulation results were around 10%.

关键词： pipe elbow erosion wear spiral flow swirler guide vane parameters particle collision

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collisional Penrose process of 4D rotational Einstein-Gauss-Bonnet black holes

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Chinese Physics C 2021年第5期45卷 212-222页

作者： Yunlong Liu Xiangdong Zhang Department of Physics South China University ofTechnologyGuangzhou 510641China

The collisional Penrose process of massive spinning particles in a rotational Einstein-Gauss-Bonnet(EGB) black hole background is studied. By numerically solving the equations of motion for spinning particles, we find that the energy extraction efficiency increases monotonically with the decrease of the EGB coupling parameterα. Moreover, the efficiency η increases as the particle spin s grows. We also find that the energy extraction efficiency increases with the decrease of the EGB coupling parameter α. When the EGB coupling constant α = 0, our results reduce to the Kerr case, which has been investigated previously.

关键词： Penrose process Gauss Bonnet gravity particle collision

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collision of spinning particles near BTZ black holes

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Chinese Physics C 2020年第6期44卷 169-175页

作者： Xulong Yuan Yunlong Liu Xiangdong Zhang School of Physics South China University of TechnologyGuangzhou 510641China

We study the collision property of spinning particles near a Banados-Teitelboim-Zanelli(BTZ)black *** results show that although the center-of-mass energy of two ingoing particles diverges if one of the particles possesses a critical angular momentum,the particle with critical angular momentum cannot exist outside of the horizon due to violation of the timelike *** detailed investigation indicates that only a particle with a subcritical angular momentum is allowed to exist near an extremal rotating BTZ black hole,and the corresponding collision center-of-mass energy can be arbitrarily large in a critical angular momentum limit.

关键词： BTZ black hole particle collision BSW mechanism

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FLOW STRUCTURE FORMATION AND EVOLUTION IN CIRCULATING GAS-FLUIDIZED BEDS

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China Particuology 2004年第1期2卷 1-12页

作者： JieLi J.A.M.Kuipers MaterialsScienceDivision ArgonneNationalLaboratoryArgonneIL.60439USA DepartmentofChemicalEngineering TwenteUniversityEnschede7500AETheNetherlands

The occurrence of heterogeneous flow structures in gas-particle flows seriously affects the gas-solid contacting and transport processes in high-velocity gas-fluidized beds. particles do not disperse uniformly in the flow but pass through the bed in a swarm of clusters. The so-called 揷ore-annulus?structure in the radial direction and 揝?shaped axial distribution of solids concentration characterize the typical flow structure in the system. A computational study, using the discrete particle approach based on molecular dynamics techniques, has been carried out to explore the mechanisms underlying formation of the clusters and the core-annulus structure. Based on energy budget analysis including work done by the drag force, kinetic energy, rotational energy, potential energy, and energy dissipation due to particle-particle and particle-wall collisions, the role of gas-solid interaction and inelastic collisions between the particles are elucidated. It is concluded that the competition between gas-solid interaction and particle-particle interaction determines the pattern formation in high-velocity gas-solid flows: if the gas-solid interaction (under elevated pressure) dominates, most of particle energy obtained by drag from the gas phase is partitioned such that particle potential energy is raised, leading to a uniform flow structure. Otherwise, a heterogeneous pattern exists, which could be induced by both particle-particle collisions and gas-solid interaction. Although both factors could cause the flow instability, the non-linear drag force is demonstrated to be the necessary condition to trigger heterogeneous flow structure formation. As gas velocity increases and goes beyond a critical value, the fluid-particle interaction suppresses particle collisional dissipation, and as a consequence a more homogeneous flow regime is formed.

关键词： flow structures particle collision gas-solid interaction nonlinear drag circulating gas-fluidized beds

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