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A geometric algorithm based on the advancing front approach for sequential sphere packing

GRANULAR MATTER 2018年第4期20卷 59-59页

作者： Li, Yongjun Ji, Shunying Dalian Univ Technol State Key Lab Struct Anal Ind Equipment Dalian Peoples R China

The arrangement of calculation samples with a high initial solid fraction and lower computation times are the primary concern of discrete element simulations. When generating thousands of particles, the advancing front algorithm, as one of the effective constructive packing methods, provides a time-saving and non-overlapping packing methodology compared to dynamic approaches, which are extremely time consuming in these situations. This paper proposes a sequential packing algorithm based on the advancing front approach. New particles with random sizes are sequentially inserted into a predefined void space to make contact with at least three existing neighboring particles by analytically solving the trilateration equations. The algorithm allows for an arrangement of particles with random sizes to obtain a low-porosity particle assembly. To increase the algorithm efficiency, a feasible measure of the spatial gridding is proposed to simplify the detection of the advancing fronts. The generated packings can be isotropic, and the number of contacts per particle is sufficiently high to reach a stable state. When the generated packing structures are filled with particles, the physical properties, including the average coordination number, solid fraction, second-order fabric tensor, contact orientation and particle size distribution, are analyzed with different size ratios. Examples of practical geometric models for real industrial applications to railway ballast and a gear are presented.

关键词： Sequential sphere packing geometric algorithm Advancing front approach Spatial gridding Discrete element method geometrical isotropy

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Approximation of triangular B-spline surfaces by local geometric fitting algorithm

Approximation of triangular B-spline surfaces by local geome...

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3rd National-Foundation-for-Science-and-Technology-Development Conference on Information and Computer Science (NICS)

作者： Nga Le-Thi-Thu Khoi Nguyen-Tan Thuy Nguyen-Thanh Danang Univ Sci & Technol Danang Vietnam Vietnam Natl Univ Hanoi Vietnam

ISBN: (纸本)9781509020980

Surfaces over triangular domain are a powerful and flexible tool for modeling of complex objects with non-rectangular topology. Due to the particular advantages of triangular parametric surfaces, they have wide application and prospect in computer aided design and reverse engineering. The interpolation or approximation problem for reconstructing an arbitrary topological parametric surface from scattered data points or polygonal mesh is one of the significant research areas. This paper deals with the approximation of triangular B-spline surfaces based on a local geometric fitting algorithm and an inverse Loop subdivision scheme. The reconstructed triangular B-spline with the low degree crosses through most of the given data points of an initial triangular mesh. The accuracy of the obtained triangular B-spline surfaces can he carried out by changing the position of control points in the local geometric algorithm as well as a number of the inverse subdivision times. Finally, we demonstrate the effectiveness of the proposed method with some experimental examples.

关键词： Parametric surface triangular B-splines geometric algorithm inverse subdivision approximation

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Exact and efficient search-based wall distance algorithm for partitioned unstructured grids

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COMPUTERS & FLUIDS 2025年 288卷

作者： Oh, Jun Seok Kung, Tae Yoon Kim, Kyu Hong Seoul Natl Univ Dept Aerosp Engn 105-401 Gwanak Ro Seoul 08826 South Korea Seoul Natl Univ Inst Adv Aerosp Technol Seoul 08826 South Korea

In this paper, we develop a novel search-based wall distance calculation algorithm. The algorithm is highly efficient and satisfies the crucial requirement of exactness in wall distance calculations, taking into account the full geometry of the discretized surface. Unlike conventional search-based algorithms that use element-wise bounding boxes or auxiliary grids, the developed algorithm employs only a set of zero-dimensional reference points representing the elements of the discretized surface. Reference points can be chosen as the centers of faces, the centers of edges, or the vertices. The conservative relation between the approximate distance using one of these references and the exact distance is established, allowing for the efficient extraction of element candidates using only low-level information. The algorithm does not require complex pre-processing of the surface or any information about the query points, ensuring high software modularity. An intuitive load balancing procedure is also proposed to address the load imbalance arising from partitioning-based parallelization. Numerical test demonstrates that the developed algorithm shows three orders of magnitude speed-up compared to exhaustive search and one to two orders of magnitude speed-up compared to other search-based algorithms. It also shows high parallel scalability on partitioned meshes, indicating its feasibility for large-scale problems.

关键词： geometric algorithm Minimum wall distance Tree-based algorithm Computational fluid dynamics Unstructured grids

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Comparative Study on the Vertical Column Concentration Inversion algorithm of Tropospheric Trace Gas Based on the MAX-DOAS Measurement Spectrum

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REMOTE SENSING 2024年第18期16卷 3359页

作者： Wang, Haoyue Lu, Yuehua Yu, Ke Xiao, Feihong Guo, Rongzhi Yan, Naicong Wang, Weiguo Yunnan Univ Dept Atmospher Sci Kunming 650500 Peoples R China Yunnan Meteorol Observ Kunming 650032 Peoples R China

The tropospheric vertical column concentration (VCDtrop) of NO2, SO2, and HCHO was retrieved, respectively, by employing the geometric method (Geomtry), simplified model method (Model), and look-up table method (Table) with the observation spectra of the multi-axis differential absorption spectroscopy instrument (MAX-DOAS). The correlation and relative differences of the inversion results obtained by these three algorithms, as well as the changes in quantiles, were explored. The comparative analysis reveals that the more concentrated the vertical distribution height of gas components is in the near-surface layer, the better the conformity of the VCDtrop retrieved by different algorithms. However, the increase in relative differences is also related to the diurnal variation of gas components. The influence of aerosols on the inversion of the VCDtrop is greater than the change in the vertical distribution height of the gas component itself. The near-surface concentration and distribution height of gas components are the internal factors that give rise to relative differences in the inversion of the VCDtrop by different algorithms, while aerosols are one of the extremely important external reasons. The VCDtrop inverted by Geomtry without considering the influence of aerosols is generally larger except for NO2. Model sets up aerosols in accordance with the height and meteorological conditions of the atmospheric environment. Table can invert the aerosol profile in real time. Compared with Model, it shows a significant improvement in the refined setting of aerosols. Moreover, while obtaining the vertical distribution of aerosols, it can invert the diurnal variation of the VCDtrop. The VCDtrop inverted by Table is the smallest, and the relative difference with Model is on average about 10% smaller. The relative difference of the VCDtrop for the same height (aerosol optical thickness) quantile is 7-15% (about 25% lower on average). When comparing the inversion results of Ta

关键词： multi-axis differential absorption spectroscopy geometric algorithm mode simplification method look-up table method tropospheric vertical column concentration the relative differences

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Mesh-driven resampling and regularization for robust point cloud-based flow analysis directly on scanned objects

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2024年 432卷

作者： Jaiswal, Monu Corpuz, Ashton M. Hsu, Ming-Chen Iowa State Univ Dept Mech Engn 2043 Black Engn Ames IA 50011 USA

Point cloud representations of three-dimensional objects have remained indispensable across a diverse array of applications, given their ability to represent complex real-world geometry with just a set of points. The high fidelity and versatility of point clouds have been utilized in directly performing numerical analysis for engineering applications, bypassing the laborintensive and time-consuming tasks of creating analysis-suitable CAD models. However, point clouds exhibit various levels of quality, often containing defects such as holes, noise, and sparse regions, leading to sub-optimal geometry representation that can impact the stability and accuracy of any analysis study. This paper aims to overcome such challenges by proposing a novel method that expands upon our recently developed direct point cloud-to-CFD approach based on immersogeometric analysis. The proposed method features a mesh-driven resampling technique to fill any unintended gaps and regularize the point cloud, making it suitable for CFD analysis. Additionally, ghost penalty stabilization is employed for incompressible flow to improve the conditioning and stability compromised by the small cut elements in immersed methods. The developed method is validated against standard benchmark geometries and real- world point clouds obtained in-house with photogrammetry. Results demonstrate the proposed framework's robustness in facilitating CFD simulations directly on point clouds of varying quality, underscoring its potential for practical applications in analyzing real-world structures.

关键词： Point cloud Scanned object geometric algorithm CFD Immersed method Ghost penalty

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algorithmic approach to discrete fracture network flow modeling in consideration of realistic connections in large-scale fracture networks

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第9期16卷 3798-3811页

作者： Qihua Zhang Shan Dong Yaoqi Liu Junjie Huang Feng Xiong Badong National Observation and Research Station of Geohazards China University of GeosciencesWuhan430074China SINOPEC Shanghai Engineering Co. Ltd.Shanghai200120China Faculty of Engineering China University of GeosciencesWuhan430074China

Analyzing rock mass seepage using the discrete fracture network(DFN)flow model poses challenges when dealing with complex fracture *** paper presents a novel DFN flow model that incorporates the actual connections of large-scale ***,this model efficiently manages over 20,000 fractures without necessitating adjustments to the DFN *** geometric analyses,such as identifying connected fractures,dividing the two-dimensional domain into closed loops,triangulating arbitrary loops,and refining triangular elements,are fully *** analysis processes are comprehensively introduced,and core algorithms,along with their pseudo-codes,are outlined and explained to assist readers in their programming *** accuracy of geometric analyses is validated through topological graphs representing the connection relationships between *** practical application,the proposed model is employed to assess the water-sealing effectiveness of an underground storage cavern *** analysis results indicate that the existing design scheme can effectively prevent the stored oil from leaking in the presence of both dense and sparse ***,following extensive modification and optimization,the scale and precision of model computation suggest that the proposed model and developed codes can meet the requirements of engineering applications.

关键词： Discrete fracture network(DFN)flow model geometric algorithm Fracture flow Water-sealing effect

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Research on Post Nonlinear geometric algorithm for BSS of Mixed Vibration Simulation Signals from the Impeller Pumps

Research on Post Nonlinear Geometric Algorithm for BSS of Mi...

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The second International Symposium on Socially and Technically Symbiotic Systems (STSS2015);The 7th International Symposium on Symbiotic Nuclear Power Systems (ISSNP2015)

作者： Sun Shi-yan XIA Hong CHEN Zhi-hui YANG Bo LIU Mei-ru Fundamental Science on Nuclear Safety and Simulation Technology Laboratory College of Nuclear Science and TechnologyHarbin Engineering University Science and Technology on Reactor System Design Technology Laboratory Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China

In nuclear power plants,for rotating equipment,a normal method for monitoring the modes and diagnosing its fault is monitoring and analyzing its vibration or noise ***,the detected signals are usually the non-linear mixed signals produced by multiple pieces of equipment or their different *** order to distinguish equipment's status,Blind Source Separation technique need to be applied to separate the mixed signals,then equipment's mode can be distinguished *** existing mature BSS algorithms are based on the assumption of the linear *** it to the nonlinear mixed problem directly may cause failure or result in totally wrong *** this paper,we apply geometric algorithm to separate the mixed vibration simulation *** method follows the post-nonlinear mixing model assumption,and develops its separating measure exploiting the difference between a linear mixture and a nonlinear one from their distributions in a three-dimensional *** impeller pump,which is a typical rotating machinery in nuclear power plants,is chosen as the study *** build a three-dimensional model of a kind of impeller pump,use Finite Element Analysis method to create some correlative stress and mode analysis,decorate appropriate monitoring points to get the most intense vibration simulation signal in the pump,and then construct the mixed *** using the post-nonlinear geometric algorithm,the mixed vibration simulation signals of the pump are *** with correlation coefficient,the algorithm performs *** can obtain the same vibration peak frequency from the result as that from the source signals.

关键词： Blind Source Separation post-nonlinear model geometric algorithm the impeller pump vibration simulation signal

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A fast and efficient particle packing generation algorithm with controllable gradation for discontinuous deformation analysis

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GEOMECHANICS AND GEOPHYSICS FOR GEO-ENERGY AND GEO-RESOURCES 2023年第1期9卷 1-27页

作者： Ma, Jianjun Ding, Wenjie Lin, Yuexiang Chen, Wanxiang Huang, Linchong Sun Yat Sen Univ Guangdong Res Ctr Underground Space Exploitat Tech Sch Civil Engn Southern Marine Sci & Engn Guangdong Lab ZhuhaiGu Zhuhai 519082 Peoples R China Sun Yat Sen Univ Sch Civil Engn Guangzhou 510275 Peoples R China Sun Yat Sen Univ Sch Aeronaut & Astronaut Shenzhen 518107 Peoples R China Hong Kong Polytech Univ Dept Civil & Environm Engn Hong Kong Peoples R China

A systematic geometric algorithm is developed to generate particle packing with high density, controllable gradation, and uniform spatial distribution for discontinuous deformation analysis (DDA). The algorithm incorporates a lattice searching technique to expedite overlap detection and reduce computational costs during particle packing generation. Additionally, a Fourier transformation method is utilized to analytically handle overlap detections on arbitrary irregular boundaries. To evaluate the efficiency and accuracy of the proposed method, a series of comparisons are made between existing methods and the proposed approach. Numerical modelling of engineering problems is conducted using the proposed method and a self-developed numerical program called DDA. The modelling results demonstrate that the proposed particle generation method has wide applications in generating complex particle models for discontinuous numerical analysis. The algorithm exhibits excellent performance in both geometric and numerical analyses, further confirming its efficiency and accuracy.

关键词： geometric algorithm Lattice searching algorithm Particle packing generation Discrete Fourier transforms

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Slow manifolds of classical Pauli particle enable structure-preserving geometric algorithms for guiding center dynamics

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COMPUTER PHYSICS COMMUNICATIONS 2021年 265卷 107981-107981页

作者： Xiao, Jianyuan Qin, Hong Univ Sci & Technol China Dept Plasma Phys & Fus Engn Hefei 230026 Peoples R China Princeton Univ Plasma Phys Lab POB 451 Princeton NJ 08543 USA

Since variational symplectic integrators for the guiding center was proposed [1,2], structure-preserving geometric algorithms have become an active research field in plasma physics. We found that the slow manifolds of the classical Pauli particle enable a family of structure-preserving geometric algorithms for guiding center dynamics with long-term stability and accuracy. This discovery overcomes the difficulty associated with the unstable parasitic modes for variational symplectic integrators when applied to the degenerate guiding center Lagrangian. It is a pleasant surprise that Pauli's Hamiltonian for electrons, which predated the Dirac equation and marks the beginning of particle physics, reappears in classical physics as an effective algorithm for solving an important plasma physics problem. This technique is applicable to other degenerate Lagrangians reduced from regular Lagrangians. (C) 2021 Elsevier B.V. All rights reserved.

关键词： Guiding center motion geometric algorithm Volume preserving algorithm Discrete variation Classical Pauli particle

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A new constructive algorithm for random polydisperse dense disk pack generation

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING 2021年第20期122卷 5812-5843页

作者： Lozano, Elias Gattass, Marcelo Tecgraf Inst Tech Sci Software DevelopmentPUC Rio Rio De Janeiro Brazil Pontificia Univ Catolica Rio de Janeiro Dept Informat Rio de Janeiro Brazil

This article presents a novel strategy for the non-overlapping disk-packing problem for generating dense random assemblies. The proposed geometric algorithm adopts an advancing-front approach that uses novel heuristics to determine the next positions for incoming particles with support from a polygonal mesh. Additionally, we propose strategies to improve generation at the pack's interior and near container borders. Experiments demonstrate that our algorithm outperforms previous methods in terms of the desired particle radius distribution function, packing density, and mean number of particle contacts.

关键词： advancing-front approach disk packing geometric algorithm polygonal mesh

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