共查询到20条相似文献,搜索用时 140 毫秒
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大时间步长叠波格式最初思想为LeVeque提出的大时间步长Godunov格式,通过叠加间断分解发出的强波来构造数值格式.原方法只给出了间断强波的穿越叠加方法,文章对其进行了完善,并推广到多维.针对膨胀波提出了一种网格单元分解法可以自动满足熵条件,避免出现非物理解.给出了格式的具体计算公式,并用单个守恒律方程、一维/多维Euler方程组进行了数值计算.计算结果表明,新格式除了可以采用大时间步长的优点外,在一定范围内随CFL数增加其耗散反而更低,因而对激波接触间断膨胀波的分辨率更高. 相似文献
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考察了电、磁场分量分别基于不同近似函数空间展开的一维和二维Maxwell方程间断元求解方法。结合中心数值通量和电、磁场分量近似函数空间的不同组合,构造了各种间断元算子。通过用这些算子在规则和不规则网格上编码分析一维和二维金属腔的谐振模式,详细考察了算子的收敛和伪解支持性,并据此对基函数进行了优选。算子在时域和频域对谐振模式的计算结果彼此符合良好。优选的Maxwell方程间断元算子不仅同时具备能量守恒和免于伪解的特性,且无需引入辅助变量,为设计高品质Maxwell方程间断元算法和研发相关电磁场模拟软件提供了支撑。 相似文献
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提出一种液舱横荡数值模拟的方法,将气液两相交界面视为物理间断,通过高阶精度离散格式捕捉间断.根据NVD(Normalized Variable Diagram)实现非结构化网格上高精度离散格式,建立固定网格上自由表面运动模拟方法.在开发的非结构网格有限体积法求解器GTEA(General Transport Equation Analyzer)基础上,实现上述方法.首先对经典的溃坝过程进行模拟,并与文献结果对比验证方法和程序的可信度.对二维矩形液舱在不同激振频率时的横荡进行数值计算,并与实验以及商业软件CFX计算结果进行比较.结果表明方法和软件可以模拟自由面的翻卷、破碎运动现象,对距自由面较深点处流体载荷的计算结果与实验值符合较好,与商业软件CFX相比,在相同计算网格下,算法可以更好的计算次峰值,验证方法正确可行. 相似文献
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粒子输运方程的线性间断有限元方法 总被引:1,自引:0,他引:1
将空间线性间断有限元方法应用于动态粒子输运方程的求解.数值算例表明,空间线性间断有限元方法在网格边界的数值精度方面明显高于指数格式和菱形格式,并且通量在时间上的微分曲线相对光滑,避免了指数格式、菱形格式数值解的非物理振荡现象. 相似文献
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构造矩形网格下求解Lagrangian坐标系下气动方程组的单元中心型格式. 空间离散采用控制体积间断Petrov-Galerkin方法,时间离散采用二阶TVD Runge-Kutta方法. 利用限制器来抑制非物理震荡并保证RKCV算法的稳定性. 构造的算法可以保证物理量的局部守恒. 与Runge-Kutta间断Galerkin(RKDG)方法相比较,RKCV方法的计算公式少一项积分项使得计算较简单. 给出一些数值算例验证了算法的可靠性及效率. 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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Yagawa G 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2011,87(4):115-134
The finite element method (FEM) has been commonly employed in a variety of fields as a computer simulation method to solve such problems as solid, fluid, electro-magnetic phenomena and so on. However, creation of a quality mesh for the problem domain is a prerequisite when using FEM, which becomes a major part of the cost of a simulation. It is natural that the concept of meshless method has evolved. The free mesh method (FMM) is among the typical meshless methods intended for particle-like finite element analysis of problems that are difficult to handle using global mesh generation, especially on parallel processors. FMM is an efficient node-based finite element method that employs a local mesh generation technique and a node-by-node algorithm for the finite element calculations. In this paper, FMM and its variation are reviewed focusing on their fundamental conception, algorithms and accuracy. 相似文献
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At present the design of the Lightning protection systems (LPS) for structures as stipulated in standards is based on the electro – geometrical method, which was initially used to protect power lines from lightning. A derivative of the electro-geometrical method is the rolling sphere method. This method together, with the protection angle method and mesh method are used almost in all lightning standards as the measure in installing the lightning protection systems of grounded structures. In the mesh method, the dimension of the cell size in different levels of protection is determined using the rolling sphere method. Since the rolling sphere method does not take into account the physics of the lightning attachment process there is a need to evaluate the validity of the stipulated value in standards of the minimum lightning current that can penetrate through the mesh in different levels of protection. In this paper, meshes of different sizes as stipulated in the lightning protection standards were tested for their ability to intercept lightning flashes using a lightning attachment model that takes into account the physics of connecting leaders on. The results are in reasonable agreement with the specifications given in the lightning protection standards. 相似文献
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A Straightforward $hp$-Adaptivity Strategy for Shock-Capturing with High-Order Discontinuous Galerkin Methods 下载免费PDF全文
Hongqiang Lu & Qiang Sun 《advances in applied mathematics and mechanics.》2014,6(1):135-144
In this paper, high-order Discontinuous Galerkin (DG) method is used to solve
the two-dimensional Euler equations. A shock-capturing method based on the artificial
viscosity technique is employed to handle physical discontinuities. Numerical tests
show that the shocks can be captured within one element even on very coarse grids.
The thickness of the shocks is dominated by the local mesh size and the local order
of the basis functions. In order to obtain better shock resolution, a straightforward $hp$-adaptivity strategy is introduced, which is based on the high-order contribution
calculated using hierarchical basis. Numerical results indicate that the $hp$-adaptivity
method is easy to implement and better shock resolution can be obtained with smaller
local mesh size and higher local order. 相似文献
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Yagawa G 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2011,87(4):135-151
The free mesh method (FMM) is a kind of the meshless methods intended for particle-like finite element analysis of problems that are difficult to handle using global mesh generation, or a node-based finite element method that employs a local mesh generation technique and a node-by-node algorithm. The aim of the present paper is to review some unique numerical solutions of fluid and solid mechanics by employing FMM as well as the Enriched Free Mesh Method (EFMM), which is a new version of FMM, including compressible flow and sounding mechanism in air-reed instruments as applications to fluid mechanics, and automatic remeshing for slow crack growth, dynamic behavior of solid as well as large-scale Eigen-frequency of engine block as applications to solid mechanics. 相似文献
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Zhicheng Hu & Heyu Wang 《advances in applied mathematics and mechanics.》2012,4(6):685-702
This paper deals with the application of a moving mesh method for kinetic/hydrodynamic coupling model in two dimensions. With some criteria, the
domain is dynamically decomposed into three parts: kinetic regions where fluids
are far from equilibrium, hydrodynamic regions where fluids are near thermodynamical equilibrium and buffer regions which are used as a smooth transition. The
Boltzmann-BGK equation is solved in kinetic regions, while Euler equations in hydrodynamic regions and both equations in buffer regions. By a well defined monitor function, our moving mesh method smoothly concentrate the mesh grids to the
regions containing rapid variation of the solutions. In each moving mesh step, the
solutions are conservatively updated to the new mesh and the cut-off function is rebuilt first to consist with the region decomposition after the mesh motion. In such a
framework, the evolution of the hybrid model and the moving mesh procedure can
be implemented independently, therefore keep the advantages of both approaches.
Numerical examples are presented to demonstrate the efficiency of the method. 相似文献
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含冷却水管大体积混凝土温度场计算的一种新方法 总被引:2,自引:0,他引:2
水管冷却是混凝土坝施工期的主要温度控制措施,提出一种新的水管冷却数值模拟理论和计算方法.该方法将水管置于常规混凝土单元内部,在单元中把混凝土与水管的接触面作为散热面纳入控制方程的边界条件,把混凝土通过冷却水管壁面耗散的能量叠加到常规泛函中,根据此复合泛函由变分原理建立含冷却水管混凝土的有限元支配方程.编制相应的三维计算程序,在程序中水管网格的拓扑信息由程序自动完成,冷却水管可以从混凝土单元任意位置穿过,因此不增加网格剖分的难度,算例表明该方法能准确模拟混凝土的冷却效应. 相似文献
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A new finite-difference method for the numerical solution of gas dynamics equations is proposed. This method is a uniform
monotonous finite-difference scheme of second-order approximation on time and space outside of domains of shock and compression
waves. This method is based on inputting adaptive artificial viscosity (AAV) into gas dynamics equations. In this paper, this
method is analyzed for 2D geometry. The testing computations of the movement of contact discontinuities and shock waves and
the breakup of discontinuities are demonstrated. 相似文献
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N. Fornengo 《Physics of Particles and Nuclei》2011,42(4):641-649
The particle physics interpretation of the dark matter problem, which is intimately of cosmological and astrophysical nature,
is going to be posed under deep scrutiny in the next years. From the particle physics side, accelerators like the LHC will
deeply test theoretical ideas of new physics beyond the Standard Model, where particle candidates of dark matter are predicted
to exist. From the astrophysical side, many probes are already providing a great deal of independent information on the foreseen
signals which can be produced by the galactic or extra-galactic dark matter. In all this, cosmology plays a central role in
determining the relevance and the basic properties of the particle dark matter candidate. The ultimate hope is the emergence
of dark matter signals and the rise of a coherent picture of new physics from and at the crossing of particle physics, astrophysics
and cosmology. A very ambitious and farreaching project, which will bring to a deeper level our understanding of the fundamental
laws which rule the Universe. 相似文献
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Qianlong Liu 《Journal of computational physics》2011,230(22):8256-8274
Prosperetti’s seminal Physalis method, an Immersed Boundary/spectral method, had been used extensively to investigate fluid flows with suspended solid particles. Its underlying idea of creating a cage and using a spectral general analytical solution around a discontinuity in a surrounding field as a computational mechanism to enable the accommodation of physical and geometric discontinuities is a general concept, and can be applied to other problems of importance to physics, mechanics, and chemistry. In this paper we provide a foundation for the application of this approach to the determination of the distribution of electric charge in heterogeneous mixtures of dielectrics and conductors. The proposed Physalis method is remarkably accurate and efficient. In the method, a spectral analytical solution is used to tackle the discontinuity and thus the discontinuous boundary conditions at the interface of two media are satisfied exactly. Owing to the hybrid finite difference and spectral schemes, the method is spectrally accurate if the modes are not sufficiently resolved, while higher than second-order accurate if the modes are sufficiently resolved, for the solved potential field. Because of the features of the analytical solutions, the derivative quantities of importance, such as electric field, charge distribution, and force, have the same order of accuracy as the solved potential field during postprocessing. This is an important advantage of the Physalis method over other numerical methods involving interpolation, differentiation, and integration during postprocessing, which may significantly degrade the accuracy of the derivative quantities of importance. The analytical solutions enable the user to use relatively few mesh points to accurately represent the regions of discontinuity. In addition, the spectral convergence and a linear relationship between the cost of computer memory/computation and particle numbers results in a very efficient method. In the present paper, the accuracy of the method is numerically investigated by example computations using one dielectric particle, one isolated conductor particle, one conductor particle connected to an external source with imposed voltage, and two conductor/dielectric particles with strong interactions. The efficiency of the method is demonstrated with one million particles, which suggests that the method can be used for many important engineering applications of broad interest. 相似文献