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multiscale modeling of the atmospheric environment over a forest canopy

Science China Earth Sciences 2020年第6期63卷 875-890页

作者： Chao YAN Shiguang MIAO Yujue LIU Guixiang CUI Institute of Urban Meteorology China Meteorological AdministrationBeijing 100089China Institute of Atmospheric Physics Chinese Academy of SciencesBeijing 100029China Department of Engineering Mechanics Tsinghua UniversityBeijing 100084China

Vegetation constitutes one of the fundamental types of land use on Earth.The presence of trees in urban areas can decrease local winds and exchange sensible and latent heat with the surrounding environments,thus exerting notable influences on the urban microenvironment.A better understanding of the turbulent transfer of momentum and scalars around vegetation canopy could significantly contribute to improvement of the urban environment.This work develops a large-eddy simulation(LES)method that is applicable to model the flow and scalar transport over the forest canopy.We study the atmospheric flow over complex forested areas under typical weather conditions by coupling LES to the mesoscale model.Models of radiation and energy balance have been developed with explicit treatment of the vegetation canopy.By examining the flow over a forest canopy under a range of stability conditions,we found that buoyancy enhances or suppresses turbulent mixing in unstable or stable atmosphere respectively,with decreasing or increasing wind shear,respectively.From the multiscale modeling of the Beijing Olympic Forest Park,the present coupling scheme proves to better resolve the diurnal variations in wind speed,temperature,and relative humidity over complex urban terrains.The coupling scheme is superior to the traditional mesoscale model in terms of wind field simulation.This is mainly because the coupling scheme not only takes the influences of external mesoscale flow into consideration,but also resolves the heterogeneous urban surface at a fine scale by downscaling,thus better reproducing the complex flow and turbulent transport in the urban roughness sublayer.

关键词： Urban forest environment Canopy turbulence Large eddy simulation multiscale modeling

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multiscale modeling of mechanical behavior and failure mechanism of 3D angle-interlock woven aluminum composites subjected to warp/weft directional tension loading

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Chinese Journal of Aeronautics 2021年第8期34卷 202-217页

作者： Zhenjun WANG Siyuan YANG Shiping SUN Yingfeng ZHANG Changchun CAI Bowen XIONG Wei YANG Zhifeng XU Huan YU School of Aeronautical Manufacturing Engineering Nanchang Hangkong UniversityNanchang 330063China Hunan Aviation Powerplant Research Institute Aero Engine Corporation of ChinaZhuzhou 412002China School of Mechanical Engineering Northwestern Polytechnical UniversityXi'an 710072China

The mechanical behavior and progressive damage mechanism of novel aluminum matrix composites reinforced with 3D angle-interlock woven carbon fibers were investigated using a multiscale modeling approach.The mechanical properties and failure of yarns were evaluated using a microscale model under different loading scenarios.On this basis,a mesoscale model was developed to analyze the tensile behavior and failure mechanism of the composites.The interfacial decohesion,matrix damage,and failure of fibers and yarns were incorporated into the microscopic and mesoscopic models.The stress–strain curves and fracture modes from simulation show good agreement with the experimental curves and fracture morphology.Local interface and matrix damage initiate first under warp directional tension.Thereafter,interfacial failure,weft yarn cracking,and matrix failure occur successively.Axial fracture of warp yarn,which displays a quasi-ductile fracture characteristic,dominates the ultimate composites failure.Under weft directional tension,interfacial failure and warp yarn rupture occur at the early and middle stages.Matrix failure and weft yarn fracture emerge simultaneously at the final stage,leading to the cata-strophic failure of composites.The weft directional strength and fracture strain are lower than the warp directional ones because of the lower weft density and the more serious brittle fracture of weft yarns.

关键词： Aluminum matrix composites Failure mechanism Mechanical behavior Progressive damage multiscale modeling

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Method of cells-based multiscale modeling of elastic properties of filament wound C/C-SiC including free Si and matrix porosity

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Journal of Materials Science & Technology 2019年第12期35卷 2906-2918页

作者： Evan J.Pineda Marek Fassin Stefanie Reese Jaan-Willem Simon NASA Glenn Research Center 21000 Brookpark RoadMS 49/7ClevelandOH 44135United States Institute for Applied Mechanics RWTH Aachen UniversityMies-van-der-Rohe-Str.152074 AachenGermany

Three different multiscale models, based on the method of cells(generalized and high fidelity) micromechanics models were developed and used to predict the elastic properties of C/C-SiC composites. In particular, the following multiscale modeling strategies were employed: Concurrent modeling of all phases using the generalized method of cells, synergistic(two-way coupling in space) multiscale modeling with the generalized method of cells, and hierarchical(one-way coupling in space) multiscale modeling with the high fidelity generalized method of cells. The three models are validated against data from a hierarchical multiscale finite element model in the literature for a repeating unit cell of C/C-SiC.Furthermore, the multiscale models are used in conjunction with classical lamination theory to predict the stiffness of C/C-SiC plates manufactured via a wet filament winding and liquid silicon infiltration process recently developed by the German Aerospace Institute. Finally, un-reacted Si(or free Si) and porosity in the C matrix are included in the multiscale model, and the effect of these new phases on the stiffness and local stresses are considered.

关键词： multiscale modeling C/C-SiC Ceramic matrix composites

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Compositional colored Petri net approach to multiscale modeling for systems biology

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International Journal of modeling, Simulation, and Scientific Computing 2014年第4期5卷 106-122页

作者： Fei Liu Ming Yang Control and Simulation Center Harbin Institute of Technology West Dazhi Street 92 HarbinHeilongjiangP.R.China

Colored Petri nets have been demonstrated as a powerful tool for modeling multiscale systems biology.However,the construction of colored Petri nets for biological systems requires prior knowledge about colored Petri nets and is often error-prone and cum-bersome for biologists,especially when the communication between components and hierarchical organization of components in a multiscale model are an issue.To address this problem,an established way is to develop small components and then compose them into bigger models.In this paper,we present a compositional colored Petri net approach to aid automatic modeling of systems biology,and demonstrate it with two case stud-ies.We focus on the modeling of communication between components and hierarchical organization of components as they are key to build multiscale models.

关键词： Colored Petri nets compositional modeling multiscale modeling systems biology

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Sequential multiscale modeling Using Sparse Representation

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Communications in Computational Physics 2008年第10期4卷 1025-1033页

作者： Carlos J.Garcıa-Cervera Weiqing Ren Jianfeng Lu Weinan E Mathematics Department University of CaliforniaSanta BarbaraCA 93106USA Courant Institute of Mathematical Sciences New York UniversityNew YorkNY 10012USA Program in Applied and ComputationalMathematics Princeton UniversityPrincetonNJ 08544USA Department of Mathematics and PACM Princeton UniversityPrincetonNJ 08544USA

The main obstacle in sequential multiscale modeling is the pre-computation of the constitutive relationwhich often involvesmany independent variables.The constitutive relation of a polymeric fluid is a function of six variables,even after making the simplifying assumption that stress depends only on the rate of strain.Precomputing such a function is usually considered too expensive.Consequently the value of sequential multiscale modeling is often limited to“parameter passing”.Here we demonstrate that sparse representations can be used to drastically reduce the computational cost for precomputing functions of many variables.This strategy dramatically increases the efficiency of sequential multiscale modeling,making it very competitive in many situations.

关键词： multiscale modeling sparse grids

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Experimental and numerical investigation of mechanical behavior of plain woven CFRP composites subjected to three-point bending

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Chinese Journal of Aeronautics 2023年第7期36卷 505-517页

作者： Qiaoli ZHAO Yuliang HOU Weihan WANG Yutong LIU Cheng LI School of Mechanical and Power Engineering Zhengzhou UniversityZhengzhou 450001China

The mechanical behavior of plain woven Carbon Fiber-Reinforced Polymer(CFRP)composites under Three-Point Bending(TPB)is investigated via experimental and numerical approaches.multiscale models,including microscale,mesoscale and macroscale models,have been developed to characterize the TPB strength and damages.Thereinto,Representative Volume Elements(RVEs)of the microscale and mesoscale structures are established to determine the effective properties of carbon-fiber yarn and CFRP composites,respectively.Aimed at accurately and efficiently predicting the TPB behavior,an Equivalent Cross-Ply Laminate(ECPL)cell is proposed to simplify the inherent woven architecture,and the effective properties of the subcell are computed using a local homogenization approach.The macroscale model of the TPB specimen is constructed by a topology structure of ECPL cells to predict the mechanical behavior.The TPB experiments have been performed to validate the multiscale models.Both the experimental and numerical results reveal that delamination mainly appears in the top and bottom interfaces of the CFRP laminates.And matrix cracking and delamination are identified as the significant damage modes during the TPB process.Finally,the quasi-static and dynamic behaviors of plain woven composites are discussed by comparing the results of Low-Velocity Impact(LVI)and TPB simulations.

关键词： Equivalent Cross-Ply Laminate(ECPL)cell Local homogenization multiscale modeling Plain woven CFRP composites Three-Point Bending(TPB)behavior

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Nonequilibrium Dynamics of Chemically Active Particles

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Chinese Journal of Chemistry 2022年第3期40卷 419-429页

作者： Huijun Jiang Zhonghuai Hou Hefei National Laboratory for Physical Sciences ot the Microscale&Technology of China HefeiAnhui 230026China

Chemically active motion is ubiquitous in many nature and artificial systems where each unit can move directionally by converting chemical energy into kinetic energy.Since the systems are driven by activity far from equilibrium,many dynamical behaviors forbidden in equilibrium systems may be induced.Nonequilibrium dynamics of such systems is then a hot multidisciplinary topic with great challenges.Here,we review our recent theoretical advances in some fundamental problems at the single active particle level,the collective behavior level,as well as in systems where active particles act as baths.

关键词： Statistical mechanics Nonequilibrium processes Kinetics Chemically active particle multiscale modeling

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Toward atomistic models of intact severe acute respiratory syndrome coronavirus 2 via Martini coarsegrained molecular dynamics simulations

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Quantitative Biology 2023年第4期11卷 421-433页

作者： Dali Wang Jiaxuan Li Lei Wang Yipeng Cao Bo Kang Xiangfei Meng Sai Li Chen Song Center for Quantitative Biology Academy for Advanced Interdisciplinary StudiesPeking UniversityBejingChina Peking-Tsinghua Center for Life Sciences BeijingChina Tianjin Medical University Cancer Institute and Hospital National Clinical Research Center for CancerTianjinChina National Supercomputer Center in Tianjin TianjinChina Bejing Frontier Research Center for Biological Structure State Key Laboratory of Membrane BiologySchool of Life SciencesTsinghua UniversityBeijingChina

The causative pathogen of coronavirus disease 2019(COVID-19),severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),is an enveloped virus assembled by a lipid envelope and multiple structural proteins.In this study,by integrating experimental data,structural modeling,as well as coarse-grained and all-atom molecular dynamics simulations,we constructed multiscale models of SARS-CoV-2.Our 500-ns coarse-grained simulation of the intact virion allowed us to investigate the dynamic behavior of the membrane-embedded proteins and the surrounding lipid molecules in situ.Our results indicated that the membrane-embedded proteins are highly dynamic,and certain types of lipids exhibit various binding preferences to specific sites of the membrane-embedded proteins.The equilibrated virion model was transformed into atomic resolution,which provided a 3D structure for scientific demonstration and can serve as a framework forfuture exascale allatom molecular dynamics(MD)simulations.A short all-atom molecular dynamics simulation of 255 ps was conducted as a preliminary test for largescale simulationsofthis complexsystem.

关键词： enveloped virus molecular dynamics simulation multiscale modeling SARS-CoV-2

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Highly Thermo-Conductive Three-Dimensional Graphene Aqueous Medium

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Nano-Micro Letters 2020年第10期12卷 224-235页

作者： Zheng Bo Chongyan Ying Huachao Yang Shenghao Wu Jinyuan Yang Jing Kong Shiling Yang Yanguang Zhou Jianhua Yan Kefa Cen State Key Laboratory of Clean Energy Utilization Institute for Thermal Power EngineeringCollege of Energy EngineeringZhejiang University38 Zheda RoadHangzhou 310027People’s Republic of China ZJU-Hangzhou Global Scientific and Technological Innovation Center Hangzhou 311215People’s Republic of China Department of Mechanical and Aerospace Engineering The Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongPeople’s Republic of China

Highly thermo-conductive aqueous medium is a crucial premise to demonstrate high-performance thermal-related applications.Graphene has the diamond comparable thermal conductivity,while the intrinsic two-dimensional reality will result in strong anisotropic thermal conductivity and wrinkles or even crumples that significantly sacrifices its inherent properties in practical applications.One strategy to overcome this is to use three-dimensional(3D)architecture of graphene.Herein,3D graphene structure with covalent-bonding nanofins(3D-GS-CBF)is proposed,which is then used as the filler to demonstrate effective aqueous medium.The thermal conductivity and thermal conductivity enhancement efficiency of 3D-GS-CBF(0.26 vol%)aqueous medium can be as high as 2.61 W m-1 K-1 and 1300%,respectively,around six times larger than highest value of the existed aqueous mediums.Meanwhile,3D-GS-CBF can be stable in the solution even after 6 months,addressing the instability issues of conventional graphene networks.A multiscale modeling including non-equilibrium molecular dynamics simulations and heat conduction model is applied to interpret experimental results.3D-GS-CBF aqueous medium can largely improve the solar vapor evaporation rate(by 1.5 times)that are even comparable to the interfacial heating system;meanwhile,its cooling performance is also superior to commercial coolant in thermal management applications.

关键词： Three-dimensional graphene Thermo-conductive aqueous medium multiscale modeling Solar thermal conversion Practical thermal management

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multiscale Mechanics and Optimization of Gastropod Shells

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Journal of Bionic Engineering 2011年第4期8卷 357-368页

作者： Mostafa Yourdkhani Damiano Pasini Francois Barthelat Department of Mechanical Engineering McGill University 817 Sherbrooke Street West Montreal QC H3A 2K6 Canada

A vast majority of mollusks grow a hard shell for protection. The structure of these shells comprises several levels of hierarchy that increase their strength and their resistance to natural threats. This article focuses on nacreous shells, which are composed of two distinct layers. The outer layer is made of calcite, which is a hard but brittle material, and the inner layer is made of nacre, a tough and ductile material. The inner and outer layers are therefore made of materials with distinct structures and properties. In this article, we demonstrate that this system is optimum to defeat attacks from predators. A two-scale mod- eling and optimization approach was used. At the macroscale, a two-layer finite element model of a seashell was developed to capture shell geometry. At the microscale, a representative volume element of the microstructure of nacre was used to model the elastic modulus of nacre as well as a multiaxial failure criterion, both expressed as function of microstructural parameters. Experiments were also performed on actual shells of red abalone to validate the results obtained from simulations and gain insight into the way the shell fails under sharp perforation. Both optimization and experimental results revealed that the shell displays optimum performance when two modes of failure coincide within the structure. Finally, guidelines for designing two-layer shells were proposed to improve the performance of engineered protective systems undergoing similar structural and loading conditions.

关键词： seashell multiscale modeling representative volume element failure criterion nacre multiscale optimization

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