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Numerical Simulations of Liquid-Solid Flows in A Vertical Pipe by MPS-DEM Coupling Method

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China Ocean Engineering 2022年第4期36卷 542-552页

作者： XIE Feng-ze MENG Qing-jie wan De-cheng Computational Marine Hydrodynamics Lab(CMHL) School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China Wuhan Second Ship Design and Research Institute Wuhan 430205China

In the process of deep-sea mining,the liquid-solid flows in the vertical transportation pipeline are very complex.In the present work,an in-house solver MPSDEM-SJTU based on the improved MPS and DEM is developed for the simulation of hydraulic conveying.Firstly,three examples including the multilayer cylinder collapse,the Poiseuille flow and two-phase dam-break are used to validate the precision of the DEM model,the pipe flow model and MPS-DEM coupling model,respectively.Then,the hydraulic conveying with coarse particles in a vertical pipe is simulated.The solid particle distribution is presented and investigated in detail.Finally,the coupling method is successfully applied for the simulation of the liquid-solid flows in a vertical pipe with rotating blades,which shows the stability of the solver under rotating boundary conditions.This fully Lagrangian model is expected to be a new approach for analyzing hydraulic conveying.

关键词： liquid-solid flows MPS DEM vertical pipe rotating boundary conditions

Coupling potential and viscous flow models with domain decomposition for wave propagations

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Journal of Hydrodynamics 2022年第5期34卷 826-848页

作者： Wen-jie Zhong Wen-tao wang De-cheng wan Computational Marine Hydrodynamics Lab(CMHL) School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China China Ship Scientific Research Center Wuxi214082China

Either potential flow or viscous flow based model may be flawed for numerical wave simulations.The two-way coupling of potential and viscous flow models with the domain decomposition utilizing respective strengths has been a trending research topic.In contrast to existing literatures in which closed source potential models were used,the widely used open source OceanWave3D,OpenFOAM-v2012 are used in the present research.An innovative overlapping two-way coupling strategy is developed utilizing the ghost points in OceanWave3D.To guarantee computational stability,a relaxation zone used both for outlet damping and data transfer is built over the overlapping region in OceanWave3D.The free surface elevation in the relaxation zone is directly probed in OpenFOAM while the velocity potential is indirectly built upon its temporal variation which is calculated by the free surface boundary condition using the probed velocity.Strong coupling is achieved based on the fourth-order Runge-Kutta(RK)algorithm.Both two-and three-dimensional tests including linear,nonlinear,irregular,and multi-directional irregular waves,are conducted.The effectiveness of the coupling procedure in bidirectional data transfer is fully demonstrated,and the model is validated to be accurate and efficient,thus providing a competitive alternative for ocean wave simulations.

关键词： Domain decomposition numerical wave tank potential/viscous flow coupling irregular waves wave-structure interaction

Correlation analysis between underwater noise and Liutex for DTMB4119 propeller

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Journal of Hydrodynamics 2022年第4期34卷 585-595页

作者： Lian-jie Yu Jian-wei Wu De-cheng wan Computational Marine Hydrodynamics Lab(CMHL) School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China Wuhan Second Ship Design and Research Institute Wuhan 430205China

Propeller is an important equipment of ocean structures.It has characteristics of complex geometry and periodic vortex shed,which means high research value.This paper takes DTMB419 propeller as the research object.A detailed study is conducted on the wake vortices in non-cavitation state and cavitation state.Three vortex identification methods are used to compare the vortices capture effects from downstream sections and three-dimensional perspectives.The results show that,the third-generation vortex identification technologyΩ_(R)shows obvious advantages.At the same time,FW-H equation is used to predict propeller noise,and the relationship between nonlinear sound source distribution and vortices distribution is analyzed.It is found that the distribution of Lighthill tensor is consistent withΩ_(R),which proves the advantages and potential of third-generation vortex identification technology from acoustic perspective.

关键词： Third-generation vortex DTMB4119 propeller cavitation FW-H formulation

Application of Lattice Boltzmann Method to Simulate Forest Edge

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Advances in Applied Mathematics and Mechanics 2023年第2期15卷 376-401页

作者： jie Wei Jianjun Wu An Jiang Kun wan Key Laboratory of Mechanics on Disaster and Environment inWestern China Attached to the Ministry of Education of ChinaLanzhou UniversityLanzhouGansu 730000China College of Civil Engineering and Mechanics Lanzhou UniversityLanzhouGansu 730000China Shenzhen TenFong Technology Co. LtdGuangdongChina ZhongJiao TianHe Machinery Equipment Manufacturing Co.LTD SuzhouJiangsuChina

This study is focused on the forest edge flow by using numerical method.To model the effects of a forest canopy on airflow,source terms are introduced into the governing equations.The lattice Boltzmann method in conjunction with the standard k-εmodel is applied to solve the turbulent wind field.In order to perform the simulation on non-uniform grids,the Taylor series expansion and least square based lattice Boltzmann method(TLLBM)is adopted to improve the accuracy and computational efficiency.The present method and code are verified with an earlier forest edge simulation.A series of forest canopies are established to explore the impacts of canopy morphology on wind field.These canopies cover 3 canopy architectures and the Leaf Area Index(LAI)ranges from 2.0 to 4.0.The further study is carried out by adjusting the canopy foliage amount and the canopy architecture.The present study demonstrates the potential of lattice Boltzmann method to simulate the high Re number forest edge flow.The impacts of canopy morphology on zero plane displacement,aerodynamic roughness length,friction wind velocity,permeability coefficient,wall-shear stress are illustrated in detail.The results show that the canopy sub-layer wind field,especially the wind velocity profiles within and above the forest canopy,are mainly determined by canopy morphology.

关键词： Forest edge lattice Boltzmann method non-uniform grids canopy morphology

Effect of Cu loading content on the catalytic performance of Cu-USY catalysts for selective catalytic reduction of NO with NH_(3)

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Journal of Environmental Sciences 2023年第4期126卷 445-458页

作者： Jie Wan Haipeng Yang Yijun Shi Yanjun Liu Jin Zhang Jun Zhang Gongde Wu Renxian Zhou Energy Research Institute Nanjing Institute of TechnologyNanjing 211167China Institute of Catalysis Zhejiang UniversityHangzhou 310028China

Series of Cu-USY zeolite catalyst with different Cu loading content were synthesized through simple impregnation method.The obtained catalysts were subjected to selective catalytic reduction of NOxwith NH_(3)(NH_(3)-SCR) performance evaluation,structural/chemical characterizations such as X-ray diffraction (XRD),N2adsorption/desorption,H_(2)temperature-programmed reduction (H_(2)-TPR),NH_(3)temperature-programmed desorption (NH_(3)-TPD) as well as detailed in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments including CO adsorption,NH_(3)adsorption and NO+O_(2)in situ reactions.Results show that Cu-USY with proper Cu loading (in this work 5Cu-USY with5 wt.%Cu) could be promising candidates with highly efficient NH_(3)-SCR catalytic performance,relatively low byproduct formation and excellent hydrothermal stability,although its SO_(2)poisoning tolerability needs alleviation.Further characterizations reveal that such catalytic advantages can be attributed to both active cu species and surface acid centers evolution modulated by Cu loading.On one hand,Cu species in the super cages of zeolites increases with higher Cu content and being more conducive for NH_(3)-SCR reactivity.On the other hand,higher Cu loading leads to depletion of Br?nsted acid centers and simultaneous formation of abundant Lewis acid centers,which facilitates NH_(4)NO_(3)reduction via NH_(3)adsorbed on Lewis acid centers,thus improving SCR reactivity.However,Cu over-introduction leads to formation of surface highly dispersed CuOx,causing unfavorable NH_(3)oxidation and inferior N2selectivity.

关键词： NH_(3)-SCR USY zeolite Cu species Brønsted/Lewis acid centers Diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)

Rule acquisition of three-way semi-concept lattices in formal decision context

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CAAI Transactions on Intelligence Technology 2024年第2期9卷 333-347页

作者： jie Zhao Renxia wan Duoqian Miao Boyang Zhang School of Mathematics and Information Science North Minzu UniversityYinchuanNingxiaChina Department of Computer Science and Technology Tongji UniversityShanghaiChina Department of Computer Science Bowling Green State UniversityBowling GreenOhioUSA

Three-way concept analysis is an important tool for information processing,and rule acquisition is one of the research hotspots of three-way concept analysis.However,compared with three-way concept lattices,three-way semi-concept lattices have three-way operators with weaker constraints,which can generate more concepts.In this article,the problem of rule acquisition for three-way semi-concept lattices is discussed in general.The authors construct the finer relation of three-way semi-concept lattices,and propose a method of rule acquisition for three-way semi-concept lattices.The authors also discuss the set of decision rules and the relationships of decision rules among object-induced three-way semi-concept lattices,object-induced three-way concept lattices,classical concept lattices and semi-concept lattices.Finally,examples are provided to illustrate the validity of our conclusions.

关键词： finer relation rule acquisition three-way concept analysis three-way semi-concept lattices

Solar Flare Forecast Model Based on Resampling and Fusion Method

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Research in Astronomy and Astrophysics 2022年第8期22卷 238-248页

作者： Jie Wan Jun-Feng Fu Dai-Min Tan Ke Han Meng-Yao Yu Peng E Laboratory for Space Environment and Physical Sciences Harbin Institute of TechnologyHarbin 150001China School of Electrical Engineering and Automation Harbin Institute of TechnologyHarbin 150001China School of Computer and Information Engineering Harbin University of CommerceHarbin 150028China

Predicting the activity of solar flares is of great significance for studying its physical mechanism and the impact on human production and life.Problems such as class imbalance,high time-series sensitivity,and over-localization of important features exist in the sample data used for flare forecasting.We design a solar flare fusion method based on resampling and the CNN-GRU algorithm to try to solve the above problems.In order to verify the effectiveness of this fusion method,first,we compared the forecast performance of different resampling methods by keeping the forecast model unchanged.Then,we used the resampling algorithm with high performance to combine some single forecast models and fusion forecast models respectively.We use the 2010-2017 sunspot data set to train and test the performance of the flare model in predicting flare events in the next 48 h.Through the conclusion of the above steps,we prove that the resampling method SMOTE and its variant SMOTE-ENN are more advantageous in class imbalance problem of flare samples.In addition,after the fusion of one-dimensional convolution and recurrent network with"forget-gate",combined with the SMOTE-ENN to achieve TSS=61%,HSS=61%,TP_(Rate)=77%and TN_(Rate)=83%.This proves that the fusion model based on resampling and the CNN-GRU algorithm is more suitable for solar flare forecasting.

关键词： (Sun:)sunspots Sun:flares Sun:X-rays gamma-rays Sun:magnetic fields Sun:corona

An Attention-Based Friend Recommendation Model in Social Network

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Computers, Materials & Continua 2020年第12期65卷 2475-2488页

作者： Chongchao Cai Huahu Xu Jie Wan Baiqing Zhou Xiongwei Xie School of Computer Engineering and Science Shanghai UniversityShanghai200444China College of Logistic and Information Engineering Huzhou Vocational&Technical CollegeHuzhou313000China Google New YorkUSA

In social networks,user attention affects the user’s decision-making,resulting in a performance alteration of the recommendation systems.Existing systems make recommendations mainly according to users’preferences with a particular focus on items.However,the significance of users’attention and the difference in the influence of different users and items are often ignored.Thus,this paper proposes an attention-based multi-layer friend recommendation model to mitigate information overload in social networks.We first constructed the basic user and item matrix via convolutional neural networks(CNN).Then,we obtained user preferences by using the relationships between users and items,which were later inputted into our model to learn the preferences between friends.The error performance of the proposed method was compared with the traditional solutions based on collaborative filtering.A comprehensive performance evaluation was also conducted using large-scale real-world datasets collected from three popular location-based social networks.The experimental results revealed that our proposal outperforms the traditional methods in terms of recommendation performance.

关键词： Friend recommendation collaborative filtering attention mechanism deep learning

Strain Softening of Styrene-Isoprene-Styrene Copolymers under Large Amplitude Oscillatory Shear for Clarifying Payne Effect in Rubbers and Their Nanocomposites

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Chinese Journal of Polymer Science 2023年第1期41卷 153-165页

作者： Xin-Peng Fan Yi-Hu Song Qiang Zheng wan-Jie Wang MOE Key Laboratory of Macromolecular Synthesis and Functionalization Department of Polymer Science and EngineeringZhejiang UniversityHangzhou310027China Shanxi-Zheda Institute of New Materials and Chemical Engineering Taiyuan030000China College of Materials Science and Engineering Henan Key Laboratory of Advanced Nylon Materials and ApplicationZhengzhou UniversityZhengzhou450001China

To illustrate mechanisms of Payne effect in rubbers and their nanocomposites experiencing large amplitude oscillatory shear(LAOS),comparison studies were performed in styrene-isoprene-styrene(SIS)copolymers and their selectively crosslinked materials at temperatures below and above glass transition temperature of the polystyrene(PS)phase.It was found that under periodic dynamic shear,the strain softening is reversible when the polyisoprene(PI)phase,either crosslinked or not,is restricted by hard PS domains but it shows hysteresis once the PS domains disassociate.The strain softening can happen at the time scale of intrinsic Rouse relaxation of elastically active network strands.Critical stress of strain softening scales with number density of elastically active network strands,a simple relation being verified not only in the selectively crosslinked SIS copolymers but also in PI gum vulcanizates and carbon black filled PI compounds.Payne effect is traditionally used to term strain softening of highly filled rubber vulcanizates under LAOS deformation while evidenced herein is that the Payne effect of highly filled rubber vulcanizates shares the mechanism being common to the strain softening of SIS copolymers.

关键词： Large amplitude oscillatory shear SIS Rubber nanocomposites Strain softening