共查询到20条相似文献,搜索用时 31 毫秒
1.
提出了一个基于二维轮廓序列的四面体网格生成方法,用于医学图像三维几何模型重构.该方法首先对各选定的断层图像提取目标轮廓并做分支匹配等处理,然后生成各轮廓内部平面域的三角网格,最后在相邻断层之间根据三角网格连接四面体单元.该方法被应用于人体膝关节虚拟手术系统的三维几何建模,得到的膝部股骨模型包含494个节点和2 046个四面体单元,膝部脂肪模型包含2 854个节点和14011个四面体单元,这些模型被成功地应用于膝关节手术仿真,从而证明了该三维模型重建方法的可行性和有效性. 相似文献
2.
为了更合理地进行四面体网格剖分,提出了一种根据待剖分对象形态不同进行网格密度自适应调整的四面体网格剖分方法。该方法首先采用BCC(body-centered cubic)网格初始化网格空间,并根据表面曲率的大小以及距离物体表面的远近,采用LEPP(longest edge propagation path)算法由外至内对初始化后的网格空间进行不同尺度的细分;然后对横跨表面的网格进行调整,以形成对象的表面形态;最后采用以质量函数引导的拉普拉斯平滑与棱边收缩(edge collapse)的方法对网格的质量进行优化来最终得到待剖分对象的四面体网格。结果表明,该方法所生成的网格不仅具有自适应的网格密度,而且网格质量比常用的Advancing Front算法也有所提高。对于基于3维断层图像或表面模型进行有限元建模,该方法不失为一种行之有效的好方法。 相似文献
3.
二维几何特征自适应有限元网格生成(二)--算法描述 总被引:2,自引:2,他引:0
以Delaunay三角剖分为基础,构造几何特征自适应有限元网格单元尺寸信息场,给出动态节点一单元一体化生成算法,实现二维形体几何特征自适应有限元网格的自动生成,并使分析对象力学特性得到一定程度的自适应. 相似文献
4.
《Advances in Engineering Software》2006,37(2):85-96
In the whole ship structure and vibration analysis, the FEA (finite element analysis) model of whole ship structure is required in the early design stage before the 3D CAD model is defined. Because ship structure has a complex curved surface, and many associated structural members, the whole ship analysis modeling job has become a time consuming job. For the effective support of the whole ship analysis modeling, a method to generate the analysis model using initial design information within the ship design process, hull form offset data and compartment data, is developed. To easily handle initial design information and FE model information, a flexible data structure is proposed. An automatic quadrilateral mesh generation algorithm using initial design information to satisfy the constraints imposed by the ship structure is also proposed. With the proposed data structure and mesh generation algorithm, whole ship analysis modeling job for various ship types can be effectively supported and these results are presented. 相似文献
5.
《Advances in Engineering Software》2002,33(7-10):389-402
In this paper, a mesh generation and mesh refinement procedure for adaptive finite element (FE) analyses of real-life surface structures are proposed. For mesh generation, the advancing front method is employed. FE meshes of curved structures are generated in the respective 2D parametric space of the structure. Thereafter, the 2D mesh is mapped onto the middle surface of the structure. For mesh refinement, two different modes, namely uniform and adaptive mesh refinement, are considered. Remeshing in the context of adaptive mesh refinement is controlled by the spatial distribution of the estimated error of the FE results. Depending on this distribution, remeshing may result in a partial increase and decrease, respectively, of the element size. In contrast to adaptive mesh refinement, uniform mesh refinement is characterized by a reduction of the element size in the entire domain. The different refinement strategies are applied to ultimate load analysis of a retrofitted cooling tower. The influence of the underlying FE discretization on the numerical results is investigated. 相似文献
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This paper describes a method for creating a well-shaped, layered tetrahedral mesh of a thin-walled solid by adapting the surface triangle sizes to the estimated wall thickness. The primary target application of the method is the finite element analysis of plastic injection molding, in which a layered mesh improves the accuracy of the solution. The edge lengths of the surface triangles must be proportional to the thickness of the domain to create well-shaped tetrahedrons; when the edge lengths are too short or too long, the shape of the tetrahedron tends to become thin or flat. The proposed method creates such a layered tetrahedral mesh in three steps: (1) create a preliminary tetrahedral mesh of the target geometric domain and estimate thickness distribution over the domain; (2) create a non-uniform surface triangular mesh with edge length adapted to the estimated thickness, then create a single-layer tetrahedral mesh using the surface triangular mesh; and (3) subdivide tetrahedrons of the single-layer mesh into multiple layers by applying a subdivision template. The effectiveness of the layered tetrahedral mesh is verified by running some experimental finite element analyses of plastic injection molding. 相似文献
8.
A new, efficient 3D mesh generation algorithm, hexahedral mesh for urban terrains (HeMUT), is presented. HeMUT is developed under .NET and builds unstructured/structured hexahedral meshes. The algorithm focuses on urban terrains and on the mesh generation for the simulation of toxic gases dispersion (finite element). HeMUT is fully automated, multi-threading and takes advantage of terrain. In addition, it distributes the nodes on the domain by employing a method based on process design considerations. These features decrease the computational effort and at the same time differentiate this algorithm from all other similar ones. In comparison with a commercial software HeMUT performed well. 相似文献
9.
三维实体有限元自适应网格规划生成 总被引:2,自引:0,他引:2
为实现三维实体有限元网格自适应生成,设计了中心点、沿指定曲线和基于实体表面等网格加密生成方式;并根据分析对象几何特征和物理特性经验估计,以规划的方式构造自适应网格单元尺寸信息场.在此基础上,提出基于Delaunay剖分的动态节点单元一体化算法,生成几何特征和物理特性整体自适应的有限元网格. 相似文献
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One of the demands for three dimensional (3D) finite element analyses is the development of an automatic hexahedral mesh generator.
For this problem, several methods have been proposed by many researchers. However, reliable automatic hexahedral mesh generation
has not been developed at present. In this paper, a new strategy of fully automatic hexahedral mesh generation is proposed.
In this strategy, the prerequisite for generating a hexahedral mesh is a quadrilateral surface mesh. From the given surface
mesh, combinatorial dual cycles (sheet loops for the whisker-weaving algorithm) are generated to produce a hexahedral mesh.
Since generating a good quality hexahedral mesh does not depend only on the quality of quadrilaterals of the surface mesh
but also on the quality of the sheet loops generated from it, a surface mesh modification method to remove self-intersections
from sheet loops is developed. Next, an automatic hexahedral mesh generator by the improved whisker-weaving algorithm is developed
in this paper. By creating elements and nodes on 3D real space during the weaving process, it becomes possible to generate
a hexahedral mesh with fewer bad-quality elements. Several examples will be presented to show the validity of the proposed
mesh generation strategy. 相似文献
12.
An improved grid-based algorithm for the adaptive generation of hexahedral finite element mesh is presented in this paper. It is named as the inside-out grid-based method and involves the following four steps. The first step is the generation of an initial grid structure which envelopes the analyzed solid model completely. And the elements size and density maps are constructed based on the surface curvature and local thickness of the solid model. Secondly, the core mesh is generated through removing all the undesired elements using even and odd parity rules. The third step is to magnify the core mesh in an inside-out manner through a surface node projection process using the closest position approach. To match the mesh to the characteristic boundary of the solid model, a minimal Scaled Jacobian criterion is employed. Finally, in order to handle the degenerated elements and improve the quality of the resulting mesh, two comprehensive techniques are employed: the insertion technique and collapsing technique. The present method was applied in the mesh construction of different engineering problems. Scaled Jacobian and Skew metrics are used to evaluate the hexahedral element mesh quality. The application results show that all-hexahedral element meshes which are well-shaped and capture all the geometric features of the original solid models can be generated using the inside-out grid-based method presented in this paper. 相似文献
13.
Joachim Schöberl 《Computing and Visualization in Science》1997,1(1):41-52
In this paper, the algorithms of the automatic mesh generator NETGEN are described. The domain is provided by a Constructive
Solid Geometry (CSG). The whole task of 3D mesh generation splits into four subproblems of special point calculation, edge
following, surface meshing and finally volume mesh generation. Surface and volume mesh generation are based on the advancing
front method. Emphasis is given to the abstract structure of the element generation rules. Several techniques of mesh optimization
are tested and quality plots are presented.
Received: 11 December 1996 / Accepted: 21 February 1997 相似文献
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《Parallel Computing》1997,23(9):1349-1363
In this paper we describe parallel computational methods for 3D simulation of the dynamics and fluid dynamics of a parafoil with prescribed, time-dependent shape changes. The mathematical model is based on the time-dependent, 3D Navier-Stokes equations governing the incompressible flow around the parafoil and Newton's law of motion governing the dynamics of the parafoil, with the aerodynamic forces acting on the parafoil calculated from the flow field. The computational methods developed for these 3D simulations include a stabilized space-time finite element formulation to accommodate for the shape changes, special mesh generation and mesh moving strategies developed for this purpose, iterative solution techniques for the large, coupled nonlinear equation systems involved, and parallel implementation of all these methods on scalable computing systems such as the Thinking Machines CM-5. As an example, we report 3D simulation of a flare maneuver in which the parafoil velocity is reduced by pulling down the flaps. This simulation requires solution of over 3.6 million coupled, nonlinear equations at every time step of the simulation. 相似文献
16.
提出一种基于侧影轮廓进行三维模型重建的新方法,将传统的三维锥形交叉问题转换成二维轮廓交叉问题。首先,将不同视角下的二维侧影轮廓反投影到若干个平行的三维平面上,然后在三维平面上计算所有反投影轮廓的交叉轮廓,最后对相邻三维平面上的交叉轮廓进行匹配并重建物体的表面。理论分析和实验结果表明该算法的时间复杂度和视角数目呈线性关系。由于该方法主要以增加视角数目来提高模型的精确度,所以比三维锥形交叉的方法能更快速地重建物体精确的三维模型。 相似文献
17.
提出一种满足多种准则的动态搜索优化图象重建方法。从图象场的本质出发,设立了3个准则函数。熵函数的导数是非线性的,本文将其变换为近似的线性公式以获得迭代公路。动态搜索则尽可能避免很多算法在迭代过程中对图象校正过量或不足的问题。 相似文献
18.
三维实体仿真建模的网格自动生成方法 总被引:3,自引:0,他引:3
有限元网格模型的生成与几何拓扑特征和力学特性有直接关系。建立网格模型时,为了更真实地反映原几何形体的特征,在小特征尺寸或曲率较大等局部区域网格应加密剖分;为提高有限元分析精度和效率,在待分析的开口、裂纹、几何突变、外载、约束等具有应力集中力学特性的局部区域,网格应加密剖分。为此,该文提出了基于几何特征和物理特性相结合的网格自动生成方法。该方法既能有效地描述几何形体,又能实现应力集中区域的网格局部加密及粗细网格的均匀过渡。实例表明本方法实用性强、效果良好。 相似文献
19.
Marco Livesu Alessandro Muntoni Enrico Puppo Riccardo Scateni 《Computer Graphics Forum》2016,35(7):237-246
We propose a novel method for the automatic generation of structured hexahedral meshes of articulated 3D shapes. We recast the complex problem of generating the connectivity of a hexahedral mesh of a general shape into the simpler problem of generating the connectivity of a tubular structure derived from its curve‐skeleton. We also provide volumetric subdivision schemes to nicely adapt the topology of the mesh to the local thickness of tubes, while regularizing per‐element size. Our method is fast, one‐click, easy to reproduce, and it generates structured meshes that better align to the branching structure of the input shape if compared to previous methods for hexa mesh generation. 相似文献
20.
Masroor Hussain Muhammad Abid Mushtaq Ahmad Ashfaq Khokhar Arif Masud 《International journal of parallel programming》2011,39(6):717-745
This paper investigates a high performance implementation of an Arbitrary Lagrangian Eulerian moving mesh technique on shared
memory systems using OpenMP environment. Moving mesh techniques are considered an integral part of a wider class of fluid
mechanics problems that involve moving and deforming spatial domains, namely, free-surface flows and Fluid Structure Interaction
(FSI). The moving mesh technique adopted in this work is based on the notion of nodes relocation, subjected to a certain evolution
as well as constraint conditions. A conjugate gradient method augmented with preconditioning is employed for solution of the
resulting system of equations. The proposed algorithm, initially, reorders the mesh using an efficient divide and conquer
approach and then parallelizes the ALE moving mesh scheme. Numerical simulations are conducted on the multicore AMD Opteron
and Intel Xeon processors, and unstructured triangular and tetrahedral meshes are used for the 2D and 3D problems. The quality
of generated meshes is checked by comparing the element Jacobians in the reference and current meshes, and by keeping track
of the change in the interior angles in triangles and tetrahedrons. Overall, 51 and 72% efficiencies in terms of speedup are
achieved for both the parallel mesh reordering and ALE moving mesh algorithms, respectively. 相似文献