共查询到20条相似文献,搜索用时 125 毫秒
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提出一种利用多项式和阶跃函数构造N×M涡卷的构造方法.利用蔡氏电路,传统的利用多项式函数只能产生双涡卷、三涡卷,在此基础上,通过多项式平移得到相空间x方向的多涡卷,再通过多项式与阶跃函数组合来扩展相空间中指标2的鞍焦平衡点,使得多涡卷向y方向延伸,从而生成网格多涡卷混沌吸引子.该构造方法的主要特征是通过光滑曲线和非光滑曲线的组合生成网格多涡卷混沌吸引子,能通过调整自然数N和M的值实现平面网格任意涡卷混沌吸引子阵列.理论分析、数值模拟和电路仿真证实了方法的可行性.
关键词:
网格多涡卷混沌吸引子
蔡氏电路
阶跃函数
电路实现 相似文献
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针对声学有限元分析中四节点等参单元计算精度低,对网格质量敏感的问题,将光滑有限元法引入到多流体域耦合声场的数值分析中,提出了二维多流体域耦合声场的光滑有限元解法。该方法在Helmholtz控制方程与多流体域耦合界面的声压/质点法向速度连续条件的基础上,得到二维多流体耦合声场的离散控制方程,并采用光滑有限元的分区光滑技术将声学梯度矩阵形函数导数的域内积分转换形函数的域边界积分,避免了雅克比矩阵的计算。以管道二维多流体域耦合内声场为数值分析算例,研究结果表明,与标准有限元相比,对单元尺寸较大或扭曲严重的四边形网格模型,光滑有限元的计算精度更高。因此光滑有限元能很好地应用于大尺寸单元或扭曲严重的网格模型下二维多流体域耦合声场的预测,具有良好的工程应用前景。 相似文献
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提出一种在自由重映移动网格下的广义黎曼问题方法模拟反应流.该方法基于显式的自由重映移动网格广义黎曼问题的解.为保证在时间和空间上的高精度,应用广义黎曼问题方法构造数值通量.为保证反应区的高分辨率,采用变分法生成自适应移动网格.该方法不仅能够保证网格质量,而且能有效地避免任意拉格朗日—欧拉方法中由于显式重映过程而带来的数值误差.包括CJ爆轰及不稳定爆轰的数值实验说明该格式的精确性和鲁棒性,证明这种移动网格下的二阶广义黎曼问题方法可以较好地捕捉反应流的间断与光滑结构. 相似文献
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SPH后处理研究 总被引:1,自引:0,他引:1
提出一套相对完整的光滑粒子流体动力学(SPH)后处理方法.凸区域和严重变形的非凸区域上的SPH计算结果都可用该方法处理.首先,对SPH粒子集进行Delaunay三角化,可得到由粒子作为节点的三角单元集;根据每个单元中三个节点是否彼此为粒子作用对,决定是否将该单元从单元集中删除.将保留下的单元作为有限单元并利用它们节点上的函数值,根据有限元插值方法即可得单元内部任何一点的函数值.根据该方法,可提取介质的自由表面.数值算例表明方法可行.对含固体壁面、严重粒子飞溅、多重介质互相作用的情况,提出相应对策;为SPH以至其它无网格方法形成较通用的后处理软件提供可行的途径. 相似文献
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光滑质点流体动力学(SPH)方法(综述) 总被引:32,自引:1,他引:31
综合介绍了一种新的纯(Lagrangian方法——光滑质点流体动力学(SPH)方法,由于它计算空间导数时不需要使用网格,从而避免了高维拉氏差分网格法中的网格缠结和扭曲的麻烦,它对非对称的和内含真空区域的三维问题特别有效。重点介绍了该方法的理论基础,流体动力学方程组的推导,人为粘性和热传导,自引力、汇和磁场,光滑核的选取,以及SPH执行过程等有关问题 相似文献
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在哈特曼波前测量过程中,需要对哈特曼图像进行网格划分用于计算波前斜率。传统的网格划分方法通过观察哈特曼图像手动调整网格位置和网格间距。该方法不但需要人工干预,还给波前实时测量带来困难。为实现哈特曼图像网格划分的自动化,研究了基于相关法的哈特曼图像网格自动划分方法。该方法首先对哈特曼图像进行自相关求取网格行列数以及网格间距,然后利用该网格建立相应的模拟光斑图像,最后对模拟光斑图像和哈特曼图像进行互相关求取网格最佳位置。该方法无需人工干预,耗时短,实现了网格实时自动划分。 相似文献
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航天器可重复使用防热结构通常需要采用数值模拟,进行外流场和结构热响应的耦合计算。本文针对前缘类热结构的差分计算中,关于不规则(不能用初等函数表示)区域的热响应计算,应用流场计算的思路,探讨了任意坐标变换和代数网格的生成。给出了有关控制方程、边界条件的处理方法,为进一步耦合计算提供了有关基础。 相似文献
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A high-order cut-cell method for numerical simulation of hypersonic boundary-layer instability with surface roughness 总被引:2,自引:0,他引:2
Laminar-turbulent transition of hypersonic boundary layers can be affected significantly by the existence of surface roughness. Currently many important mechanisms of roughness-induced transition are not well understood. In recent years, direct numerical simulation (DNS) has been extensively applied for investigating instability and transition mechanisms of hypersonic boundary layers. Most of the past DNS studies, however, have been based on body-fitted grids for smooth surfaces without roughness. Due to complex geometry of embedded roughness, the use of body-fitted grids can be very difficult for flow with arbitrary surface roughness. In this paper, we present a new high-order cut-cell method to overcome the natural complexities in grid generation around arbitrary surface of roughness. The new method combines a non-uniform-grid finite-difference method for discrete grid points near the solid boundary and a shock-fitting method for the treatment of the bow shock. The non-uniform-grid finite-difference formulas are expressed in a general explicit form so that they can be applied to different multi-dimensional problems without any modification. The computational accuracy of new algorithms of up to O(h4) are tested on several one- and two-dimensional elliptic equations in irregular domains. In addition, the new method is applied to the simulation of the receptivity process of a Mach 5.92 flow over a flat plate under the combined effect of an isolated surface roughness element and surface blow and suction. A good agreement is found between the unsteady flow results and those obtained by a Linear Stability Theory (LST). 相似文献
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光学空间滤波过程的计算机仿真 总被引:20,自引:2,他引:18
提出了一种利用MATLAB软件并通过计算机仿真光学空间滤波实验过程的新方法.其特点是:既可以随意改变所设计滤波器的参量,又可以对输入图象进行振幅、相位或复合滤波,并且可实现傅里叶变换频谱中相位信息的提取、存储和利用,因而能够完成一般光学实验中往往难以实现的某些操作.并分别给出了网格滤波、低通、高通及相位滤波等仿真实验结果.这种仿真实验给光学滤波器的设计和图象处理带来很大方便,同时也为相关器件的设计提供了一条新的途径. 相似文献
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In spectral-like resolution-WENO hybrid schemes,if the switch function takes more grid points as discontinuity points,the WENO scheme is often turned on,and the numerical solutions may be too dissipative.Conversely,if the switch function takes less grid points as discontinuity points,the hybrid schemes usually are found to produce oscillatory solutions or just to be unstable.Even if the switch function takes less grid points as discontinuity points,the final hybrid scheme is inclined to be more stable,provided the spectral-like resolution scheme in the hybrid scheme has moderate shock-capturing capability.Following this idea,we propose nonlinear spectral-like schemes named weighted group velocity control(WGVC)schemes.These schemes show not only high-resolution for short waves but also moderate shock capturing capability.Then a new class of hybrid schemes is designed in which the WGVC scheme is used in smooth regions and the WENO scheme is used to capture discontinuities.These hybrid schemes show good resolution for small-scales structures and fine shock-capturing capabilities while the switch function takes less grid points as discontinuity points.The seven-order WGVC-WENO scheme has also been applied successfully to the direct numerical simulation of oblique shock wave-turbulent boundary layer interaction. 相似文献
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贴体坐标系下模型加力室的大涡模拟 总被引:1,自引:0,他引:1
本文利用贴体网格对带V形槽稳定器模型加力燃烧室素流化学反应流流动进行大涡模拟的研究。采用区域法生成模型加力燃烧室的二维贴体网格,并采用多区域耦合法进行区域之间的数据传递,求解加力室整体流场。采用k方程亚网格尺度模型和亚网格EBU燃烧模型分别估算其亚网格紊流粘性和化学反应速率,用热通量辐射模型估算辐射通量,并用交错网格下SIMPLE算法和混合差分格式求解离散方程,壁面函数处理固壁边界条件。计算结果显示了稳定器后面的回流区气流结构,所得的热态流场模拟结果与实验比较吻合,表明采用贴体网格对模型加力燃烧室进行大涡模拟能真实反映流体流动及燃烧过程。 相似文献
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Upender K. Kaul 《Journal of computational physics》2010,229(17):5966-5979
A new procedure for generating smooth uniformly clustered three-dimensional structured elliptic grids is presented here which formulates three-dimensional boundary constraints by extending the two-dimensional counterpart1 presented by the author earlier. This fully automatic procedure obviates the need for manual specification of decay parameters over the six bounding surfaces of a given volume grid. The procedure has been demonstrated here for the Mars Science Laboratory (MSL) geometries such as aeroshell and canopy, as well as the Inflatable Aerodynamic Decelerator (IAD) geometry and a 3D analytically defined geometry. The new procedure also enables generation of single-block grids for such geometries because the automatic boundary constraints permit the decay parameters to evolve as part of the solution to the elliptic grid system of equations. These decay parameters are no longer just constants, as specified in the conventional approach, but functions of generalized coordinate variables over a given bounding surface. Since these decay functions vary over a given boundary, orthogonal grids around any arbitrary simply-connected boundary can be clustered automatically without having to break up the boundaries and the corresponding interior or exterior domains into various blocks for grid generation. The new boundary constraints are not limited to the simply-connected regions only, but can also be formulated around multiply-connected and isolated regions in the interior. The proposed method is superior to other methods of grid generation such as algebraic and hyperbolic techniques in that the grids obtained here are C2 continuous, whereas simple elliptic smoothing of algebraic or hyperbolic grids to enforce C2 continuity destroys the grid clustering near the boundaries. 相似文献
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