共查询到18条相似文献,搜索用时 62 毫秒
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计算含动边界非定常流动的无网格算法 总被引:1,自引:0,他引:1
在无网格算法中考虑了含动边界的流动问题,研究了可以计算处理包含一定位移及扭转动边界非定常流动的算法. 创建了无网格算法的动点法则,并引入抗扭方法对弹簧方法进行改进来处理离散点运动,提高了方法的可用度及精度. 发展了求解基于无网格的ALE方程组的算法,在点云离散的基础上采用曲面逼近计算空间导数及HLLC格式计算数值通量,运用四步龙格-库塔法进行时间推进. 在跨、超音速条件下,计算模拟了典型翼型简谐振动流场,计算结果与实验结果及文献对比吻合,验证了该算法的正确性. 相似文献
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含有启动压力梯度的渗流问题及其无网格解法 总被引:8,自引:2,他引:6
针对两种典型的涉及启动压力梯度的渗流问题,给出了无量纲化的渗流控制方程、初始条件和边界条件,并使用无网格方法进行数值模拟。计算结果使用Gringarten—Bourdet图版进行井底压力分析,给出了一种计算动边界位置的方法,并详细讨论了动边界变化情况。 相似文献
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不连续体的数值模拟尤其是动态裂纹的追踪问题一直是工程界研究的热点和难点问题。无网格方法仅仅需要结点信息,非常适合于求解这类问题。基于单位分解思想,在移动最小二乘近似函数(MLS)中根据裂纹面的不连续位移增加一个Heaviside函数,在裂尖则增加四个扩展函数描述渐进裂纹位移场;应用Galerkin方法推导了平衡方程的离散线性方程,并给出了求解裂纹问题应力强度因子的计算公式。与其他类型的扩展无网格相比,在裂尖处近似函数不需要使用可视准则,很容易生成r1/2奇异;另一个优势是影响域并没有因为裂纹的存在而改变,不会降低方程的稀疏性,求解效率较高。数值算例表明,该方法能方便有效地模拟不连续问题,具有十分广阔的应用空间。 相似文献
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带源参数的二维热传导反问题的无网格方法 总被引:1,自引:1,他引:1
利用无网格有限点法求解带源参数的二维热传导反问题,推导了相应的离散方程. 与
其它基于网格的方法相比,有限点法采用移动最小二乘法构造形函数,只需要节点信息,不
需要划分网格,用配点法离散控制方程,可以直接施加边界条件,不需要在区域内部求积分.
用有限点法求解二维热传导反问题具有数值实现简单、计算量小、可以任意布置节点等优点.
最后通过算例验证了该方法的有效性. 相似文献
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It is weN-known that the standard Galerkin is not ideally suited to deal with the spatial discretization of convection-dominated problems. In this paper, several techniques are proposed to overcome the instabilitY issues in convection-dominated problems in the simulation with a meshless method. These stable techniques included nodal refinement, enlargement of the nodal influence domain, full upwind meshless technique and adaptive upwind meshless technique. Numerical results for sample problems show that these techniques are effective in solving convection-dominated problems, and the adaptive upwind meshless technique is the most effective method of all. 相似文献
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基于改进的移动最小二乘(MLS)二阶导数近似,建立了一种求解弹性静力问题的无网格弱-强形式结合法(MLS-MWS)。该方法采用节点离散求解域,通过MLS构造形函数,将求解域划分为边界域和内部域,并分别使用控制方程的局部弱形式和强形式来建立离散系统方程。对强形式中涉及的近似函数二阶导数计算,提出了一种将其转化为求两次一阶导数的方法,与传统方法相比,该方法计算简单、精度高。MLS-MWS法结合了弱、强形式无网格法的优点,Neumann边界条件容易满足,并且只需在边界区域进行积分。文中应用该方法分析了两个弹性力学平面问题,分析结果表明本文方法具有良好的精度和收敛性。 相似文献
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The meshless manifold method is based on the partition of unity method and the finite cover approximation theory which provides a unified framework for solving problems dealing with both continuum with and without discontinuities. The meshless manifold method employs two cover systems. The mathematical cover system provides the nodes for forming finite covers of the solution domain and the partition of unity functions. And the physical cover system describes geometry of the domain and the discontinuous surfaces in the domain. The shape functions are derived by the partition of unity and the finite covers approximation theory. In meshless manifold method, the mathematical finite cover approximation theory is used to model cracks that lead to interior discontinuities in the displacement. Therefore, the discontinuity is treated mathematically instead of empirically by the existing methods. However, one cover of a node is divided into two irregular sub-covers when the meshless manifold method is used to model the discontinuity. As a result, the method sometimes causes numerical errors at the tip of a crack. To improve the precision of the meshless manifold method, the enriched methods are introduced in this work for crack problems. 相似文献
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This paper uses the element‐free Galerkin (EFG) method to simulate 2D, viscous, incompressible flows. The control equations are discretized with the standard Galerkin method in space and a fractional step finite element scheme in time. Regular background cells are used for the quadrature. Several classical fluid mechanics problems were analyzed including flow in a pipe, flow past a step and flow in a driven cavity. The flow field computed with the EFG method compared well with those calculated using the finite element method (FEM) and finite difference method. The simulations show that although EFG is more expensive computationally than FEM, it is capable of dealing with cases where the nodes are poorly distributed or even overlap with each other; hence, it may be used to resolve remeshing problems in direct numerical simulations. Flows around a cylinder for different Reynolds numbers are also simulated to study the flow patterns for various conditions and the drag and lift forces exerted by the fluid on the cylinder. These forces are calculated by integrating the pressure and shear forces over the cylinder surface. The results show how the drag and lift forces oscillate for high Reynolds numbers. The calculated Strouhal number agrees well with previous results. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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应用无网格局部彼得洛夫-伽辽金法(MLPG)研究轴对称弹性体扭转问题,给出了矩阵形式的控制方程,发展了MLPG求解轴对称体弹性扭转问题的数值计算方法。算例分析表明:此方法对求解此类问题具有良好的适应性,数值解能达到理想的计算精度。 相似文献
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基于配点法和楔形基函数,提出了一种新的求解对流扩散边值问题的无网格方法。通过一维和二维的问题验证了该数值方法的可行性;并根据数值算例和分析,可以看到该数值方法能达到满意的收敛效果。该数值方法的隐格式形式能够有效地消除对流占优问题的数值振荡现象,是一种真正的无网格方法。 相似文献
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基于核重构思想的配点型无网格方法的研究--一维问题 总被引:1,自引:0,他引:1
无网格方法按其离散原理可分为Galerkin型、配点型等。其中Galerkin型无网格方法的实施需要背景网格,不属于真正的无网格法;配点型无网格方法的实施不需要背景网格,是真正的无网格法。本文首先介绍了重构核点法的基本原理,然后基于核重构思想,与配点法相结合,以一维问题为例,研究了配点型无网格方法,对该方法构造过程中的近似函数及其导数的计算、修正函数的计算及方法的实现等问题进行了探讨。并结合若干典型算例,检验了其计算精度与收敛姓。 相似文献
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金属成型材料参数的反求技术 总被引:5,自引:0,他引:5
给出了快速准确地获得材料处于弹塑性大变形状态下各向异性弹塑性本构模型参数反求方法。首次提出了筛选试验测试点的活度规则,并以此来指导试验测试点的位置的选择;提出了仿真先验信息的概念,丰富了获取材料参数先验信息的途径;混合采用Levenberg—Marquardt方法和Gauss—Newton法的优化策略,给出了材料参数反求的基本公式和关键算法。数值算例表明,反求参数的初值以及反求区间的确定对于反求结果有着重要影响,为了确保反求过程的顺利进行,必须充分了解材料模型的先验信息.并充分利用筛选试验测试点的活度规则。同时效值算例计算还表明本文方法具有很高的计算精度和计算效率。 相似文献