共查询到20条相似文献,搜索用时 125 毫秒
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本文在分析自由过渡曲面设计方法的基础上,对多曲面间光滑自由过渡曲面的设计方法进行了研究,提出了多边域自由过渡曲面的分割拼接设计方法,由于采用了Bezier曲面模型,图形数据符合IGES标准,可和商品化CAD/CAM系统进行数据交换,因而可解决多曲面间的光滑自由过渡曲面的设计和数据加工问题。 相似文献
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在三角组合曲面的设计中,需要根据曲面间的拼接条件,协调求解曲面的内部控制顶点.在分析Bezier三角组合曲面设计方法的基础上,提出了Bezier三角曲面GC 连续局域设计方法. 内部分割点采用九参数三次曲面设计方法估算,由内部分割点将三角曲面分割为3个子曲面片,通过构造曲面边界的跨界过渡切矢,推导得出了3个分割子曲面的内部控制顶点的代数表达式.应用该方法,可以简化三角组合曲面的设计过程,提高三角组合曲面的设计计算速度. 相似文献
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车身外形曲面的计算机辅助几何设计中,非四边域曲面是难点之一。本文根据车身外形特别是轿车车身外形曲面的特点,提出了三角域及五边域曲央的数学模型,研究了跨界连续条件并编制了通用计算软件,而且通过实例运算证明方法的精确可靠,为车身外形曲面设计中的非四边域曲面设计提供了有效的方法。 相似文献
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基于数学规划的曲面造型方法 总被引:1,自引:0,他引:1
利用数学规划方法构造曲面是一种新颖的几何造型方法,在自由曲面设计,过渡面设计等领域具有鲜明折特点。本文比较详细地阐述了该方法的基本思想和实现方法,并就其理论根据和发展前景做了的讨论。 相似文献
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参数Bezier三角曲面的GC^1设计 总被引:1,自引:0,他引:1
本文从三次Bezier三角曲面片边界曲线构造入手,综合分析了计算几何中有关Bezier三角曲面GC^1拼接设计的理论和方法。针对3D离散数据曲面插值问题,全面讨论了Bezier三角曲面片内部Bezier顶点计算。提出了一种基于三次Bezier三角曲面片内部Bezier顶点d111选取优化的整体GC^1Bezier三角曲面设计方法。 相似文献
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本文主要讲述网格建模插件T-Splines在工业设计中的应用,为工业设计的曲面创建提供了新的曲面建模方法。并详细展示T-Splines从实体创建曲面、从线创建曲面和从输入曲面创建曲面的曲面案例效果。作为网格曲面、NURBS曲面的下一代的曲面建模技术,必将有广阔的发展前景。 相似文献
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蜗壳是水电站的重要部件之一,本文以包络理论推导了蜗壳曲面方程;并采用分段圆弧构造椭圆的方法构造了变径椭球包络曲面,为蜗壳曲面的几何造型提出了一种新的简便方法。同时,采用内外环面法设计了蜗壳曲面展开的计算机绘图程序,并与常用的直纹面法作了误差比较。 相似文献
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基于模型转换的IGES后处理器开发 总被引:5,自引:0,他引:5
介绍了IGES后处理器设计的全过程。该过程分为两个阶段:一是格式转换,独立于CAD/CAM系统;二是把数据映射到本地的CAD系统中,在这个阶段提出了将曲面模型转换为实体模型的方法——以曲面拼合为核心的拓扑信息重构算法。实体的拓扑信息重构分为曲面自身和曲面间的拓扑信息两部分,其中重点和难点在于曲面间的拓扑关系重构。笔者以曲面边界匹配的方法初步解决了曲面间的拓扑信息重构问题,同时引入了两种控制曲线离散精度的办法。 相似文献
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本文利用包络理论及仿射变换,提出了变经椭圆面族的包络面的求法,并在此基础上讨论了包络面的一系列几何性质。将此方法应用于水电站金属蜗壳尾部曲面的设计和曲率计算,为金属蜗壳尾部曲面的制造及应力分析提供了理论依据。 相似文献
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The smoothed particle hydrodynamics (SPH) method has proven useful for modeling large deformation of fluids including fluids with stress‐free surfaces. Because of the Lagrangian nature of the method, it is well suited to address the thermal evolution of these free surface flows. Boundary conditions at the interface of the fluid with a solid wall are usually enforced through the use of boundary particles. However, applying conditions at free surfaces, in particular gradient boundary conditions, can be problematic with traditional SPH formulations due to the degradation of the gradient approximation in these regions. Compounding this difficulty is that traditional approximations of the Laplacian operator suffer a similar degradation near free surfaces. A new SPH formulation of the Laplacian operator is presented, which improves the accuracy near free surface boundaries. This new form is based on a gradient approximation commonly used in thermal, viscous, and pressure projection problems, but includes higher‐order terms in the appropriate Taylor series. Comparisons with other approximations of second‐order derivatives are given. The discretization is tested by solving steady‐state and transient problems of thermal diffusion using the Backward Euler method with a GMRES solver. Boundary conditions are imposed through an augmented matrix. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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S. A. Barengol’ts E. A. Litvinov V. G. Suvorov I. V. Uimanov 《Technical Physics Letters》2001,27(5):370-372
The electrohydrodynamic and thermal instability development on a conducting liquid surface exposed to a strong electric field was studied by methods of two-dimensional numerical modeling. The Navier-Stokes equation was solved and the surface cone heating by the field emission current was described. It is demonstrated that the free surface evolution in this system leads to an avalanche-like growth in the cone tip temperature and the resulting explosion-like field electron emission. A considerable contribution to the liquid heating is due to a surface energy source (the Nottingham effect). The proposed computational method, based on the domain transformation to a canonical form, can be used to develop dynamic models of the liquid-metal ion source operation and to analyze the interaction of a gas plasma with a liquid metal surface in the cathode spot of a vacuum arc. 相似文献
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用偏微分方程数值解构造曲面 总被引:5,自引:0,他引:5
本文讨论四阶椭园方程一类周期问题的差分方法及在过渡面、自由曲面设计中的应用。同时通过实例讨论调整定解问题中的参数以修改曲面形状的方法。 相似文献
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R.D. Firouz-Abadi H. Haddadpour M. Ghasemi 《Engineering Analysis with Boundary Elements》2009,33(6):750-761
This paper presents the application of reduced order modeling technique for investigation of liquid sloshing in three-dimensional tanks. The governing equations of sloshing are written using a boundary element formulation for incompressible potential flow. Then, the governing equations are reduced to a more efficient form that is represented only in terms of the velocity potential on the liquid free surface. This particular form is employed for eigen-analysis of fluid motion and the sloshing frequencies and mode shapes are determined. Then, the sloshing frequencies and the corresponding right- and left-eigenvectors are used along the modal analysis technique to find a reduced order model (ROM) for fluid motion. Using a rectangular and a cylindrical tank, the results of the ROM are verified in comparison with the analytical results. Then some example tanks are used to examine the ROM in comparison with the full boundary element model for determination of the free surface motion under the angular and lateral motion of the tank. The obtained results demonstrate the capability and accuracy of the reduced order modeling technique for analysis of sloshing using a few modes. 相似文献