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Numerical simulation of tetrahedral particle mixing and motion in rotating drums

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Particuology 2018年第4期16卷 1-11页

作者： nan gui Xingtuan Yang Jiyuan Tu Shengyao Jiang Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Aclvanced Nuclear Energy Technology Key Laboratory of Advancecl Reactor Engineering and Safety of Ministry of Education Tsinghua University Beijing 100084 China School of Engineering RMIT University Melbourne VIC 3083 Australia

A regular tetrahedron is the simplest three-dimensional structure and has the largest non-sphericity. Mixing of tetrahedral particles in a thin drum mixer was studied by the soft-sphere-imbedded pseudo- hard particle model and compared with that of spherical particles. The two particle types were simulated with different rotation speeds and drum filling levels. The Lacey mixing index and Shannon information entropy were used to explore the effects of sphericity on the mixing and motion of particles. Moreover, the probability density functions and mean values and variances of motion velocities, including translational and rotational, were computed to quantify the differences between the motion features of tetrahedra and spheres. We found that the flow regime depended on the particle shape in addition to the rotation speed and filling level of the drum. The mixing of tetrahedral particles was better than that of spherical particles in the rolling and cascading regimes at a high filling level, whereas it may be poorer when the filling level was low. The Shannon information entropy is better than the Lacey mixing index to evaluate mixing because it can reflect the real change of flow regime from the cataracting to the centrifugal regime, whereas the mixing index cannot.

关键词： Tetrahedron Non-spherical particle Mixing Drum Flow regime Discrete element method

LBE simulation of impinging stream inside a T-junction mixer

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Science China(Technological Sciences) 2018年第7期61卷 1038-1055页

作者： XU WenKai ZHANG QingChen gui nan ZHANG ZiWei College of Mechanical and Transportation Engineering China University of PetroleumBeijing 102249China Beijing National Railway Research&Design Institute of Signal&Communication Co. Ltd Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyKey Laboratory of Advanced Reactor Engineering and Safety of Ministry of EducationTsinghua UniversityBeijing 100084China

Lattice Boltzmann Equation(LBE) method is utilized to simulate impinging stream(IS) in a T-junction mixer using a TD2G9 model. It aims to investigate the influence of Reynolds number(Re), aspect ratio of outlet diameter to inlet diameter, ratio of opposite inlet velocities, and the thermal boundary conditions on flow, mixing and heat transfer characteristics. In particular, the vortex evolution, velocity distribution, mixing index and Nusselt number(Nu) distribution in the T-junction mixer are explored in details. Four types of vortices and flow regimes are observed. The instantaneous and time-averaged flow and thermal fields,including vortex structure, transition of flow regimes, streamline and the Nusselt number distribution are discussed. Distinct quantitative transitions, even for dramatic change, are observed near the critical Re. At a low or moderate aspect ratio, the symmetric coherent structure is observed in an unstable flow regime. At a larger aspect ratio, the flow in the T-mixer becomes turbulent and asymmetric. The unequal injections velocities of the nozzles impose significant influence on the flow structure,mixing and heat transfer in vertical tube. Using larger difference between the two inlet velocities can result in more obvious change in flow characteristics. Moreover, mixing index is found to be valid in evaluating the mixing degree under a sinusoidal inlet velocity.

关键词： impinging flow lattice Boltzmann method T-junction heat transfer flow characteristics

Effects of volumetric fraction and included angle of composite particles on the discharge of binary mixtures in hoppers

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Particuology 2020年第4期18卷 80-90页

作者： Liange Ge nan gui Xingtuan Yang Jiyuan Tu Shengyao Jiang Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyKey Laboratory of Advanced Reactor Engineering and SafetyMinistry of EducationTsinghua UniversityBeijing 100084China School of Engineering RMIT UniversityMelbourneVIC 3083Australia

The discharge behavior of particles is important in many industrial applications,such as in the core of a pebble bed reactor,which uses a hopper bed filled with many large *** this work,a mixture composed of two particle types,freely discharged from a pebble bed,is simulated using the discreteelement *** is a spherical pebble of diameter equal to that of the fuel pebble of the *** other is a composite particle comprising three spherical pebbles bonded *** included angleαof the three pebbles characterized the particle conformation,which may affect the discharge behavior of the *** effects of volume fraction of the multi-sphere x(equivalent to the number fraction)on the discharge are also *** patterns,number flow rate,discharge velocity,and mean force of the mixture are computed to help in revealing discharge *** results show that increasing eitherαor x reduces the discharge flow *** and correlations give a quantitative evaluation of the independent effects ofαand *** analysis of velocity and force explains the mechanism relevant to the main influencing factorsαand *** results are helpful in gaining a better understanding of the discharge feature of binary mixtures and in providing a quantitative evaluation of the discharge behavior of the reactor core,especially adverse failure conditions.

关键词： Pebble flow Particle flow Discharge flow Hopper bed Binary mixture Discrete element method

Discrete element-embedded finite element model for simulation of soft particle motion and deformation

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Particuology 2022年第9期20卷 88-100页

作者： Xu Liu nan gui Xiyuan Cui Xingtuan Yang Jiyuan Tu Shengyao Jiang Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyKey Laboratory of Advanced Reactor Engineering and SafetyMinistry of EducationTsinghua UniversityBeijing 100084China School of Engineering RMIT UniversityMelbourneVIC 3083Australia

The motion and deformation of soft particles are commonly encountered and important in many appli-cations.A discrete element-embedded finite element model(DEFEM)is proposed to solve soft particle motion and deformation,which combines discrete element and finite element *** collisional surface of soft particles is covered by several dynamical embedded discrete elements(EDEs)to model the collisional external forces of the *** particle deformation,motion,and rotation are inde-pendent of each other in the *** deformation and internal forces are simulated using the finite element model,whereas the particle rotation and motion calculations are based on the discrete element *** inheriting the advantages of existing coupling methods,the contact force and contact search between soft particles are improved with the aid of the *** particle packing is simulated using the DEFEM for two cases:particle accumulation along a rectangular straight wall and a wall with an inclined *** large particle deformation in the lower layers can be simulated using current meth-ods,where the deformed particle shape is either irregular in the marginal region or nearly hexagonal in the tightly packed central *** method can also be used to simulate the deformation,motion,and heat transfer of non-spherical soft particles.

关键词： Discrete element method Finite element method Soft particle Collision Particle packing Pebble bed

Voidage correction method for DEM study of 3D pebble flows in a bed of cycloidal base

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Particuology 2024年第10期93卷 30-40页

作者： Zirui Xia Minglei Shi Quan Zou nan gui Xingtuan Yang Jiyuan Tu Shengyao Jiang Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyKey Laboratory of Advanced Reactor Engineering and SafetyMinistry of EducationTsinghua UniversityBeijing100084China Department of Engineering Physics Tsinghua UniversityBeijing100084China Department of Automation Tsinghua UniversityBeijing100084China School of Engineering RMIT UniversityMelbourneVIC3083Australia

Voidage(porosity or void fraction)in packed particles(or pebbles)is of fundamental importance in calculating the pressure drop,obtaining the drag,predicting the bed permeability,estimating the neutron streaming,*** the case when particles are deformed,a method of voidage correction during the packing state is proposed using a Discrete Element Method(DEM)simulation of 3D pebble flow inside a bed of cycloidal base.A function to evaluate the remaining volume of a pebble intercepted by horizontal and vertical planes is proposed for voidage *** that,the process of solving voidage distribution is provided in *** this method,the voidage inside the cycloidal-base pebble bed is obtained to refer to reported similar data for *** method can be potentially used for dynamical voidage calculation in CFD-DEM simulation which can get suitable voidage distribution after the correction.

关键词： Voidage Pebbleflow Packed bed Discreteelementmethod Cycloidal base KD-Tree Volume correction

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甘肃张家川县污水处理厂人工湿地工程设计

湿地科学与管理 2025年第01期21卷 75-79+85页

作者：李文泉南贵珍秦碧莲山东省环科院环境工程有限公司山东省环境保护科学研究设计院有限公司

为解决张家川县污水处理厂出水对后川河的污染问题，综合考虑当地气候条件、水量水质和地形地貌等条件，通过工艺比选，采用“水平潜流人工湿地+表面流人工湿地”的组合工艺以及人工湿地生物、物理、化学等多重作用深度处理及净化污水... 详细信息

为解决张家川县污水处理厂出水对后川河的污染问题，综合考虑当地气候条件、水量水质和地形地貌等条件，通过工艺比选，采用“水平潜流人工湿地+表面流人工湿地”的组合工艺以及人工湿地生物、物理、化学等多重作用深度处理及净化污水处理厂的出水。工程运行后，实际出水水质优于地表水准Ⅲ类标准，CODCr、NH3-N、TP去除率分别为61.5%、67.5%、53.3%，每吨水用地指标为5.78m2、建设成本为4 629元、运行成本为0.30元，运行成本远低于传统污水深度处理工艺。工程建设不仅深度净化张家川县污水处理厂出水水质，减轻后川河的污染负荷，改善河道水质，还促进工程区生态环境的改善和保护，为污水处理厂出水深度处理工艺选择提供新思路。

关键词：污水处理厂人工湿地深度处理生态修复

Liutex-based analysis of drag force and vortex in two-phase flow past 2-D square obstacle using LBM on GPU

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Journal of Hydrodynamics 2020年第5期32卷 820-833页

作者： Peng-xin Cheng nan gui Xing-tuan Yang Ji-yuan Tu Sheng-yao Jiang Hai-jun Jia Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyKey Laboratory of Advanced Reactor Engineering and Safety of Ministry of EducationTsinghua UniversityBeijing 100084China School of Engineering RMIT UniversityMelbourneAustralia

The two-phase flow past a square is a ubiquitous phenomenon widely encountered in industries and engineering,where the interaction of disparate phases coupled with the influence of the solid is rather *** this context,the flow characteristics and the vortex field are investigated to reveal the mechanisms of the two-phase drag and the vortex *** lattice Boltzmann method(LBM)is utilized to study the multi-component two-phase *** computation implemented on the GPU is remarkably accelerated thanks to the natural parallelism of the *** process of the two-phase flow past a square is thoroughly *** drag and lift forces,including the total force and the components caused by the dispersed phase and the continuous phase,respectively,are obtained,and their variation mechanisms are ***,the vortex-identification approaches based on the Liutex as well as the traditional methods are *** relationship between the bubble breakup and coalescence processes and the extremums of different vortex identification variables is analyzed.

关键词： Two-phase flow flow past a square lattice Boltzmann method(LBM) vortex identification Liutex two-phase drag

Comparative assessment and analysis of Rortex vortex in swirling jets

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Journal of Hydrodynamics 2019年第3期31卷 495-503页

作者： nan gui Liang Ge Peng-xin Cheng Xing-tuan Yang Ji-yuan Tu Sheng-yao Jiang Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy Technology Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education Tsinghua University Beijing 100084 China School of Engineering RMIT University Melbourne VIC 3083 Australia

Recently, a new definition, called Rortex, was proposed to quantify the purely rotational motion of fluids. In this work, based on the DNS data, the Rortex is used to assess and visualize the rotational motion and structure of the vortex in swirling jets in comparison with other kinds of vortex criteria, including Q , λ2,vorticity and Ω criteria. The Rortex vector,Ω, Q and criteria are found to be better than the vorticity criterion for the vortex core identification. The vector triangle formed by the Rortex R , the nonrotational shear S , and the vorticity R is analyzed to give mechanical explanations, especially of the effect of the non-rotational shear on the rotation of fluids. In addition, the probability density distributions (PDF) of the Rortex R , the nonrotational shear S, and the vorticity R are computed. The peak value of the PDF of the vorticity could be used to explain the pure rigid rotation effect and the combination effects of the rigid rotation and the non?rotational shear.

关键词： Swirling flow vortex Rortex direct numerical simulation rigid rotation non-rotational shear

Synthesis and Properties of Photodegradable Poly(furan-amine)s by a Catalyst-free Multicomponent Cyclopolymerization

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Chinese Journal of Polymer Science 2019年第10期37卷 981-989,I0004页

作者： Wei-Qiang Fu gui-nan Zhu Jian-Bing Shi Bin Tong Zheng-Xu Cai Yu-Ping Dong Beijing Key Laboratory of Construction Tailorable Advanced Functional Materials and Green Applications School of Materials Science and EngineeringBeijing Institute of Technology

A series of new photodegradable poly(furan-amine)s(PFAs) were synthesized by a one-pot, catalyst-free, multicomponent cyclopolymerization between diisocyanides, dialkylacetylene dicarboxylates, and aromatic dialdehydes. All polymerizations were conducted in toluene at 100 ℃ for 6 h without inert gas protection and furnished polymers with a satisfactory molecular weight(Mw up to32200) and yield. The PFA structure was confirmed by spectroscopic techniques, such as GPC, FTIR, and NMR, as well as by comparison with a model compound. The polymers exhibited good solubility in common organic solvents and thermal stability. All the PFAs had high refractive indices in the visible light region(400 nm to 800 nm). Moreover, the PFAs were substantially degraded by UV irradiation due to the presence of furan rings. The film thickness reduction rate could be over 90%.

关键词： Photodegradation Multicomponent reaction Catalyst-free polymerization