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Generation of orthogonal curvilinear grids on the sphere surface based on Laplace-Beltrami equations

IOP Conference Series: Earth and Environmental Science 2014年第1期19卷

作者： Fuqiang Lu Zhiyao Song Xin Fang Key Laboratory of Virtual Geographic Environment (Ministry of Education) Nanjing Normal UniversityNanjing Jiangsu Province 210046 China AA(Jiangsu Provincial Key Laboratory for Numerical Simulation of Large Scale Complex Systems School of Mathematical Sciences Nanjing Normal University Nanjing 210046 China

In this paper, Laplace-Beltrami equations are used to generate orthogonal curvilinear grids on the sphere for ocean models. In addition to overcoming the pole-problem, the grid configuration has quasi-uniform cell-size on the whole sphere. Some quantities such as the grid length along two directions, the angle deviation from orthogonality, the area of the cell to evaluate the quality of the grid, which demonstrate the grid produced is fit to be a model grid on which the finite difference method or finite volume method can be implemented for numerical simulating of global atmosphere and ocean dynamics on large scale.

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Compact Real-time Simulator with Spatial-temporal Parallel Design for large-scale Wind Farms

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CSEE Journal of Power and Energy systems 2023年第1期9卷 50-65页

作者： Hao Fu Peng Li Xiaopeng Fu Jinyue Yan Zhiying Wang Kun Wang Jianzhong Wu Chengshan Wang Key Laboratory of Smart Grid of Ministry of Education Tianjin UniversityTianjin 300072China School of Business Societyand EngineeringMlardalen UniversityVsters 72123Sweden Institute of Energy School of EngineeringCardiff UniversityCardiff CF243AAU.K

Real-time simulation of large-scale wind farms with detailed modeling can provide accurate insights into system transient behaviors,but entails challenges in computing *** paper develops a compact real-time simulator based on the field programmable gate array(FPGA)for large-scale wind farms,in which the spatial-temporal parallel design method is proposed to address the huge computation resource demand associated with detailed *** wind farm is decoupled into several subsystems based on model consistency,and the electrical system and control system of each subsystem are solved in *** the module-level pipeline technique and superscalar pipeline technique are introduced to the wind farms’simulation to effectively improve the utilization of hardware *** case studies,real-time simulations of two modified wind farms are separately carried out on a single FPGA,including one with 13 permanent magnet synchronous generators under a time-step of 11µs,and the other with 30 squirrel-cage induction generators under a time-step of 8µ*** tests,under different scenarios,are implemented to validate the numerical performance of the real-time simulator,and a comparison with the commercial tool PSCAD/EMTDC demonstrates the accuracy and effectiveness of the proposed design.

关键词： Real-time simulation FPGA wind farm spatial-temporal parallelism hardware design

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large-eddy simulation of the turbulent structure in compound open-channel flows

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ADVANCES IN WATER RESOURCES 2013年 53卷 66-75页

作者： Xie, Zhihua Lin, Binliang Falconer, Roger A. Cardiff Univ Sch Engn Cardiff CF24 3AA S Glam Wales Tsinghua Univ State Key Lab Hydrosci & Engn Beijing 10084 Peoples R China

A large-eddy simulation study has been undertaken to investigate the turbulent structure of open-channel flow in an asymmetric compound channel. The dynamic sub-grid scale model has been employed in the model, with the partial cell treatment being implemented using a Cartesian grid structure to deal with the floodplain. The numerical model was used to predict the: primary velocity and secondary currents, boundary shear stress, turbulence intensities, turbulent kinetic energy, and Reynolds stresses. These parameters were compared with experimental measurements published in the literature, with relatively close agreement being obtained between both sets of results. Furthermore, instantaneous flow fields and large-scale vortical structures were predicted and are presented herein. These vortical structures were found to be responsible for the significant lateral exchange of mass and momentum in compound channels. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.

关键词： large-eddy simulation Compound channels Turbulence Hydraulics River engineering Secondary currents

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Extendable multirate real-time simulation of active distribution networks based on field programmable gate arrays

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APPLIED ENERGY 2018年 228卷 2422-2436页

作者： Wang, Zhiying Wang, Chengshan Li, Peng Fu, Xiaopeng Wu, Jianzhong Tianjin Univ Key Lab Smart Grid Minist Educ Tianjin 300072 Peoples R China Cardiff Univ Inst Energy Sch Engn Cardiff CF24 3AA S Glam Wales

Real-time simulation of large-scale active distribution networks exhibiting a wide range of time-scales puts forward higher requirements for simulation accuracy and efficiency. This paper presents an extendable method and design for the real-time simulation of active distribution networks utilising high-performance hardware field programmable gate arrays. In the aspect of numerical algorithm, a high-accuracy and stable multirate simulation algorithm is proposed. The entire active distribution network is decoupled into different subsystems by their inherent time-scales and distinct time steps are used to solve the subsystems. Then root-matching method is adopted to form the exponential difference equations that represent the behaviours of the electric distribution network being modelled, which eliminates the truncation errors and thus provides a highly accurate time-domain solution. To handle the interface between the subsystems, a multirate interfacing method is proposed. The hardware design of the multirate interfaces is presented as well. With the multirate algorithm, a fully functional extendable real-time simulator based on field programmable gate arrays is designed and implemented. Two modified IEEE 33-node systems with photovoltaics and energy storage are simulated on the 4-field-programmable-gate-arrays-based real-time simulator. simulation results are compared with the commercial simulation tool PSCAD/EMTDC to validate the correctness and effectiveness of the proposed method and design.

关键词： Real-time simulation Field programmable gate arrays Multirate simulation Root-matching method Active distribution network

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Plant growth architecture and production dynamics : A set of e-learning resources

Plant growth architecture and production dynamics : A set of...

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International Conference on Functional-Structural Plant Growth Modeling, simulation, Visualization and Applications (FSPMA)

作者： Marc Jaeger Philippe De Reffye Sylvie Sabatier Yves Caraglio Hatem Krit Marie-Helene Lafond Véronique Letort Ep Heuvelink Matacha Motisi BaoGui Zhang Mengzhen Kang CIRAD Montpellier-Occitanie Montpellier Languedoc-Roussillon FR CentraleSupelec MAS Chatenay-Malabry 92290 France WURL HPC Group Wageningen 6700AA Netherlands China Agricultural University Beijing CN State Key Laboratory of Management and Control for Complex Systems LIAMA CASIA Beijing 100190 China

ISBN: (纸本)9781509016600

FSPM Plant and crop models are popular in the research community and there is increasing interest in their applications, from yield prediction to crop management optimization. A wide range of approaches and their software implementation can be found in the literature, with a large diversity in modelling scale (from plant organ to plot levels) and scope (structural, functional or both), as well as generic or specific aim. However, most of these approaches rely on similar key assumptions and methods related to different disciplines: botany for plant structure, eco-physiology for production, statistics and dynamic system theory for parameter identification and estimation. Web disseminated plant and crop models learning supports are not numerous, often specific, and partial. We present here a set of e-learning resources, named “Plant growth architecture and production dynamics” which describes the main notions from plant morphology and architecture, eco-physiology and applied mathematics necessary to the understanding of most plant and crop models, and their typology. In this paper, after an overview of existing learning resources on plant and crop modelling which, we believe, might be of interest for the whole research community, we present the proposed resource, which uses the GreenLab model as illustration, organized as follows: Five standalone introductive disciplinary resources; botanical notions, assumptions in eco-physiology, basis in data processing, introduction to models, introduction to GreenLab : An FSPM example in more details: GreenLab positioning, its basis, structure modelling, production modelling, and applications including model fitting and a study case ; Tools: inline (for structure analysis and statistics), online (access to fitters for instance) and access to download simulators and their documentation ; Glossary, bibliography, web site collection, and a pedagogic kit for instructors Supported by the French Sustainable Development Virtual Universit

关键词： Biological system modeling Mathematical model Agriculture numerical models Electronic learning Dynamic scheduling

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Frequency domain response of a parametrically excited riser under random wave forces

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JOURNAL OF SOUND AND VIBRATION 2014年第2期333卷 485-498页

作者： Lei, Song Zhang, Wen-Shou Lin, Jia-Hao Yue, Qian-Jin Kennedy, D. Williams, F. W. Dalian Univ Technol Fac Vehicle Engn & Mech State Key Lab Struct Anal Ind Equipment Dalian 116023 Peoples R China Cardiff Univ Cardiff Sch Engn Cardiff CF24 3AA S Glam Wales

Floating Production, Drilling, Storage and Offloading units represent a new technology with a promising future in the offshore oil industry. An important role is played by risers, which are installed between the subsea wellhead and the Tension Leg Deck located in the middle of the moon-pool in the hull. The inevitable heave motion of the floating hull causes a time-varying axial tension in the riser. This time dependent tension may have an undesirable influence on the lateral deflection response of the riser, with random wave forces in the frequency domain. To investigate this effect, a riser is modeled as a Bernoulli-Euler beam. The axial tension is expressed as a static part, along with a harmonic dynamic part. By linearizing the wave drag force, the riser's lateral deflection is obtained through a partial differential equation containing a time-dependent coefficient. Applying the Galerkin method, the equation is reduced to an ordinary differential equation that can be solved using the pseudo-excitation method in the frequency domain. Moreover, the Floquet-Liapunov theorem is used to estimate the stability of the vibration system in the space of parametric excitation. Finally, stability charts are obtained for some numerical examples, the correctness of the proposed method is verified by comparing with Monte-Carlo simulation and the influence of the parametric excitation on the frequency domain responses of the riser is discussed. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： FREQUENCY-domain analysis PARAMETER estimation WAVE forces OFFSHORE oil industry TIME-varying systems BERNOULLI-Euler method EXCITON theory

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Multiscale simulation of Power System Transients Based on the Matrix Exponential Function

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IEEE TRANSACTIONS ON POWER systems 2017年第3期32卷 1913-1926页

作者： Wang, Chengshan Fu, Xiaopeng Li, Peng Wu, Jianzhong Wang, Liwei Tianjin Univ Key Lab Smart Grid Minist Educ Tianjin 300072 Peoples R China Cardiff Univ Sch Engn Inst Energy Cardiff CF24 3AA Wales Univ British Columbia Sch Engn Kelowna BC V1V 1V7 Canada

Power system electro-magnetic transient programs (EMTP) have been popular among researchers and practitioners due to their detailed component modeling and high simulation accuracy for complex system operations. Despite broad applications in simulations with wide range of timescales, the small discretization step of these programs makes their use very time-consuming for system studies with long time span. Facing the increasingly complex power system transient characteristics and simulation demands, a multiscale algorithm that integrates the simulations of the electromagnetic and slower electromechanical transients is desirable. The multiscale simulation algorithm preserves the high fidelity of the EMTP and attains higher efficiency for the overall transient simulation. In this paper, we achieve this goal by exploiting the unique properties of the matrix exponential function. The proposed algorithm is capable of utilizing large step sizes to speed up the simulation of slow dynamics, whereas the fast transients are accurately reconstructed through efficient dense output mechanism, which is built upon the matrix exponential function computation. numerical studies including a large-scale wind farm simulation are conducted to demonstrate the effectiveness of the proposed multiscale algorithm.

关键词： Dense output formula electromagnetic transients electromechanical transients exponential integrators multiscale simulation

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A constitutive model for municipal solid waste considering mechanical creep and biodegradation-induced compression

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ACTA GEOTECHNICA 2022年第1期17卷 37-63页

作者： Gao, Wu Kavazanjian, Edward, Jr. Cardiff Univ Sch Engn Geoenvironm Res Ctr Cardiff CF24 3AA Wales Zhejiang Univ Dept Civil Engn MOE Key Lab Soft Soils & Geoenvironm Engn Hangzhou 310058 Peoples R China Arizona State Univ Sch Sustainable Engn & Built Environm Ctr Biomediated & Bioinspired Geotech Tempe AZ 85287 USA

A constitutive model is developed to describe the stress-strain-time behavior for decomposing municipal solid waste (MSW) within a critical state soil mechanics framework. The model is an extension of the Modified Cam-Clay plasticity model. In this model, three sources contribute to the hardening of MSW due to volumetric strain: time-independent plastic volumetric strain, time-dependent volumetric mechanical creep strain, and time-dependent volumetric strain due to the biodegradation (decomposition) of MSW. The MSW model was evaluated through numerical analyses of large-scale one-dimensional compression tests in the laboratory and the field and the reported vertical and horizontal deformations of a MSW landfill. The associated model parameters were obtained by compositional analysis of the waste, from values reported in the literature, and by fitting numerical results to observed behavior. For the laboratory compression test, the best-fit numerical simulation over-predicted the early settlement but converged on the experimental values after 200 days. Initially, the calculated vertical strains in the field-scale test deviated from the measured strains by up to 10% over the 398-day period of the test. However, numerical results after adjusting model parameters to provide the best fit with the measured strains resulted in a maximum deviation of less than 3% over the test duration. The calculated vertical displacements of the MSW landfill were consistent with field measurements. However, the calculated horizontal displacements were significantly lower than the measured values. Sensitivity studies showed that the time-dependent settlement predicted by the model is highly sensitive to the biodegradation rate of MSW. The good agreement between numerical values and observed vertical deformations for the SWEAP section on the MSW landfill suggests that the model has the potential to assess the performance of subsystems in landfills (e.g., the performance of a side slope liner

关键词： Biodegradation Constitutive model Hardening rule Modified Cam-Clay plasticity Municipal solid waste Time-dependent strain

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A Cartesian cut-cell based multiphase flow model for large-eddy simulation of three-dimensional wave-structure interaction

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COMPUTERS & FLUIDS 2020年 213卷 104747-104747页

作者： Xie, Zhihua Stoesser, Thorsten Yan, Shiqiang Ma, Qingwei Lin, Pengzhi Cardiff Univ Sch Engn Cardiff CF24 3AA Wales UCL Dept Civil Environm & Geomat Engn London WC1E 6DE England Univ London Sch Math Comp Sci & Engn Civil Engn London EC1V 0HB England Sichuan Univ State Key Lab Hydraul & Mt River Engn Chengdu 610065 Sichuan Peoples R China

A multiphase flow numerical approach for performing large-eddy simulations of three-dimensional (3D) wave-structure interaction is presented in this study. The approach combines a volume-of-fluid method to capture the air-water interface and a Cartesian cut-cell method to deal with complex geometries. The filtered Navier-Stokes equations are discretised by the finite volume method with the PISO algorithm for velocity-pressure coupling and the dynamic Smagorinsky subgrid-scale model is used to compute the unresolved (subgrid) scales of turbulence. The versatility and robustness of the presented numerical approach are illustrated by applying it to solve various three-dimensional wave-structure interaction problems featuring complex geometries, such as a 3D travelling wave in a closed channel, a 3D solitary wave interacting with a vertical circular cylinder, a 3D solitary wave interacting with a horizontal thin plate, and a 3D focusing wave impacting on an FPSO-like structure. For all cases, convincing agreement between the numerical predictions and the corresponding experimental data and/or analytical or numerical solutions is obtained. In addition, for all cases, water surface profiles and turbulent vortical structures are presented and discussed. (C) 2020 The Author(s). Published by Elsevier Ltd.

关键词： Two-phase flow model Wave-structure interaction Cartesian cut-cell method Finite volume method large-eddy simulation Volume-of-fluid method

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