A distortion measure to validate and generate curved high‐order meshes on CAD surfaces with independence of parameterization

A framework to validate and generate curved nodal high‐order meshes on Computer‐Aided Design (CAD) surfaces is presented. The proposed framework is of major interest to generate meshes suitable for thin‐shell and 3D finite element analysis with unstructured high‐order methods. First, we define a distortion (quality) measure for high‐order meshes on parameterized surfaces that we prove to be independent of the surface parameterization. Second, we derive a smoothing and untangling procedure based on the minimization of a regularization of the proposed distortion measure. The minimization is performed in terms of the parametric coordinates of the nodes to enforce that the nodes slide on the surfaces. Moreover, the proposed algorithm repairs invalid curved meshes (untangling), deals with arbitrary polynomial degrees (high‐order), and handles with low‐quality CAD parameterizations (independence of parameterization). Third, we use the optimization procedure to generate curved nodal high‐order surface meshes by means of an a posteriori approach. Given a linear mesh, we increase the polynomial degree of the elements, curve them to match the geometry, and optimize the location of the nodes to ensure mesh validity. Finally, we present several examples to demonstrate the features of the optimization procedure, and to illustrate the surface mesh generation process. Copyright © 2015 John Wiley & Sons, Ltd.     

丝网状镍钴硫金属化合物电化学性能研究

通过简单两步水热的方法在泡沫镍基底上成功制备出丝网状三维网络结构的Ni Co2S4,研究了材料的电化学性能,结果表明,Ni Co2S4@泡沫镍电极材料具有高的面积比电容,在电流密度为10 m A/cm~2时,面积比电容可达到2.87 F/cm~2;电流密度从10 m A/cm~2增大到50 m A/cm~2,电容保持率为60.9%;在负载量为6.21 mg/cm~2时,在30 m A/cm~2的高电流密度下充放电1 000次,电容保持率仍为67.3%。     

空间碎片高速撞击的数值模拟方法评述

计算机数值模拟是实现空间碎片撞击效应地面模拟的重要手段之一。撞击速度增加,撞击的物理机制和效应将发生改变,计算机数值模拟方法也应随之丰富和全面。介绍了基于有网格和无网格方法的高速撞击数值模拟发展历程,并针对数值模拟中常用的有限元法和SPH法进行了分析比较,阐述了高速撞击计算机模拟中无网格法的计算优势,并提出量子力学在未来无网格法数值模拟中的可能应用。为空间碎片高速撞击更加真实可靠的数值模拟提供参考。     

Erosion coupled dynamic mesh analysis for location of maximum erosion in 90-degree bends for gas-solid flows

The progressive change in the surface geometry of the component due to erosive wear affects the correct estimation of erosive wear performance and service life of the components handling particulate flows. The current study focuses on determining the change in the location of higher erosion on the bend surface during the pneumatic conveying of solids with continuous geometric modification due to erosive wear. Computational fluid dynamics (CFD) based erosion-coupled dynamic mesh methodology is adopted to simulate the time-dependent surface modification of the 90° bend geometry due to erosive wear. Available experimental data are used to validate the numerical results. Further, the erosion distribution and the location of the maximum erosion for different flow velocities, particle sizes, and bend radius ratios with the increase in solid throughput are investigated. It has been found that the modification in the bend geometry due to erosion influences the location of the maximum erosion. The increase in thickness loss due to erosion increases the variation in the location of the maximum erosion. Furthermore, an equation for predicting the location of maximum erosion of bend geometry is obtained based on the bend radius ratio and the thickness loss.     

三维复杂域四面体有限单元网格行波法生成

作为水工及岩土工程结构三维自适应有限元分析理论和软件研究的重要组成部分,在行波法的基础上,提出了一种适用于水工及岩土工程结构三维复杂区域的四面体有限单元网格的生成方法．采用了一种插值曲面,很好地考虑了地形面边界;对于多连通域,也通过合适的数据结构给以解决．文中给出了三个算例．     

一种适于大型水轮发电机磁场计算前处理的新方法

本文在采用微分法生成四边形网格的基础上,实现了大型水轮发电机有限元计算用的三角单元自动生成。在前处理技术中,提出了采用电机定子线圈轮换数进行源区加电流的新方法。     

网孔等值法在短路电流计算中的应用

阐述了网孔等值电路法在短路电流计算中的应用,推导的计算公式不仅对接有电力负荷、并 联电抗器和( 或)并联电容器的网络适用,在发电机的电势各不相等时也同样适用。算例对不 同负荷性质的计算结果进行 了分析。     

Adaptive triangular-mesh reconstruction by mean-curvature-based refinement from point clouds using a moving parabolic approximation

We use a moving parabolic approximation (MPA) to reconstruct a triangular mesh that approximates the underlying surface of a point cloud from closed objects. First, an efficient strategy is presented for constructing a hierarchical grid with adaptive resolution and generating an initial mesh from point clouds. By implementing the MPA algorithm, we can estimate the differential quantities of the underlying surface, and subsequently, we can obtain the local quadratic approximants of the squared distance function for any point in the vicinity of the target shape. Thus, second, we adapt the mesh to the target shape by an optimization procedure that minimizes a quadratic function at each step. With the objective of determining the geometrical features of the target surface, we refine the approximating mesh selectively for the non-flat regions by comparing the estimated curvature from the point clouds and the estimated curvatures computed from the current mesh. Finally, we present various examples that demonstrate the robustness of our method and show that the resulting reconstructions preserve geometric details.     

The triangular pyramid: Routing and topological properties

In this paper, a new topology for multicomputer interconnection networks, based on triangular mesh, is proposed. The new network, referred to as the triangular pyramid (or tripy for short), has L levels of triangular mesh. We study some basic important properties of the proposed network as well as introduce a routing algorithm for the tripy network based on the routing of triangular meshes. We prove that this form of pyramidal network is Hamiltonian, Hamiltonian-connected, and pancyclic. We also prove that the proposed network is 6-colorable and conduct a brief comparison of the tripy and its traditional pyramid counterpart. Our results show that the proposed network has higher scalability, connectivity, and total network bandwidth while preserving the important properties of the traditional pyramid network.