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1.
弹性波传播模拟的Chebyshev谱元法   总被引:3,自引:0,他引:3  
林伟军 《声学学报》2007,32(6):525-533
通过在每一个单元中采用谱展开近似,Chebyshev谱元法兼具了有限元处理边界及复杂结构的灵活性和谱方法的快速收敛特性,为弹性波传播的数值模拟提供了一种有效工具。从加权余量原理出发,详细阐述了Chebyshev谱元法用于弹性波传播模拟的基本理论及相应数学公式.给出了使用Chebyshev正交多项式展开得到的,存在等参变换时有关单元质量矩阵和单元刚度矩阵的精确积分公式。同时应用逐元技术极大地减少了内存和计算需求.最后,两个数值算例被用于验证这种谱元方法的高精度和强适应性。  相似文献   

2.
研究了先正向计算波前传播时间,再根据波前传播时间反向确定声线路径的三维非均匀介质声线追踪算法.在正向步骤,根据程函方程,使用基于水平集的GMM(Group Marching Method)波前扩展算法,从声源开始,逐步计算离散介质网格节点上的波前传播时间.在反向步骤,利用正向步骤计算出的网格节点上的波前传播时间,从接收点开始,向声源方向逐单元追踪声线路径.在每个长方体单元内,首先把任意点上的波前传播时间用该单元网格节点上的已知波前传播时间的线性插值函数来表示,再根据Fermat原理,提出了确定三维声线路径的方法.实验结果表明,本文方法提高了三维声线追踪的精度和计算速度.  相似文献   

3.
双相各向异性随机介质伪谱法地震波场特征分析   总被引:6,自引:0,他引:6       下载免费PDF全文
李红星  陶春辉 《物理学报》2009,58(4):2836-2842
各向异性、双相孔隙以及非均匀性是描述油气储层时应综合考虑的. 结合随机介质理论和双相介质模型建立了双相各向异性随机介质模型,采用伪谱法模拟了双相各向异性随机介质地震波场,结果表明:双相各向异性随机介质地震波场存在散射波、旅行时扰动等复杂的波场特征,这些特征强烈依赖于随机介质模型参数. 在大非均匀空间尺度下,非均匀幅度主要影响波的旅行时扰动;在小非均匀空间尺度下,非均匀幅度主要影响波的散射. 该研究使人们有可能在统计意义下反演油气储层的非均匀特征,有益于加深对地震波在油气储层中传播规律的认识. 关键词: 双相各向异性 随机介质 伪谱法 地震波  相似文献   

4.
一阶速度-应力Biot双相各向同性介质弹性波   总被引:1,自引:0,他引:1  
陈可洋 《计算物理》2011,28(3):404-412
提出一种等价的一阶双曲型速度一应力Biot双相各向同性介质弹性波波动方程,以实现双相介质混合波场中纯快慢纵波和纯横波波场分离的问题.应用散度和旋度理论证明双相介质等价方程波场分离的可行性,采用高阶交错网格有限差分法构建高精度正演算子,推导其PML吸收边界条件和稳定性条件,并对均匀双相介质和层状非均匀双相介质模型进行数值...  相似文献   

5.
王丁  张美根 《物理学报》2014,63(6):69101-069101
研究了弹性波在非均匀裂纹孔隙介质中的传播特性,建立了各向异性喷射流模型.当弹性波通过裂纹孔隙介质时,由于波的扰动及裂纹和孔隙几何结构的不一致,导致在裂纹内部及裂纹与周边孔隙之间同时存在着流体压力梯度.此时的弹性波波动响应中包含着裂纹内连通性特征和背景孔隙渗透率信息.流体的动态流动过程使得介质的等效弹性参数为复数(非完全弹性),并且具有频率依赖性.当弹性波为低频和高频极限时,介质为完全弹性;当处于中间频段时,波有衰减和频率依赖.裂纹孔隙介质的各向异性连通性(渗透率)对应着各向异性特征频率(当渗流长度等于非均匀尺度时的弹性波频率),波的传播受到裂纹内连通性的影响.在一定频段内,随着裂纹厚度的增加,将出现第二峰值,峰值大小同时受到裂纹厚度和半径的影响.  相似文献   

6.
气固两相湍流是一个复杂的多尺度,多物理场的难题.为了捕捉流场的小尺度涡以及其对颗粒的作用,传统上采用了静态的高分辨率网格,消耗极大的计算资源.本文基于小波算法对网格进行加密或疏化,从而实现网格的自适应.基于自适应网格的框架上,建立颗粒与流场分块的映射,搭建了欧拉-拉格朗日的气固两相流模拟的并行平台.通过对均匀各向同性湍...  相似文献   

7.
曹禹  杨孔庆 《物理学报》2003,52(8):1984-1992
建立了离散化网格上的准粒子体系,引入此体系的Hamilton系统描述,用来模拟声波和弹性波的传播.介绍了准粒子间相互作用的九点模型并给出互作用系数.证明了Hamilton系统方法 和声波、弹性波方程的关系,并给出两个方法中所使用物理量的关系.使用辛算法对给定的 介质模型进行数值模拟. 关键词: Hamilton系统方法 九点互作用模型 声波方程 弹性波方程 辛算法  相似文献   

8.
针对高速侵彻类战斗部在侵彻过程中的装药安定性以及在意外事故中的安全性问题,对约束结构内炸药在冲击加载下的应力波传播规律进行了模拟研究。计算了不同侵彻速度下弹体的冲击响应函数,并将具有高精度和低耗散特点的谱元法应用于约束结构内凝聚炸药中的应力波传播模拟;考虑炸药-金属界面的动摩擦特性,计算了冲击加载下由动摩擦引起的装药-壳体界面温升,以及装药内部的塑性功积累。成功地将谱元法应用于凝聚炸药中应力波传播过程的模拟,模拟结果对更准确地评估热点生成机制,以及进行装药安定性分析具有参考意义。  相似文献   

9.
林文洲  林忠  刘全 《计算物理》2017,34(3):273-282
基于非结构任意多边形网格管理体系及束缚滑移技术,针对多介质多次加卸载大变形问题的模拟,发展滑移线开穴算法,并利用金属碰撞分离模型进行验证.给出滑移线上的点和网格的开闭穴状态判别方法及网格开闭情况下滑移线上点的速度计算方法.该滑移计算技术将传统结构网格的开穴算法推广到拉氏非结构多边形网格中,保留拉氏滑移算法无缝连接和较好模拟物质界面的优点,实现了模拟实际问题中物质界面开闭功能.在金属碰撞分离模型中采用多种网格、不同界面形状和多介质等条件进行测试,证明了算法的正确性.  相似文献   

10.
为提高油藏数值模拟算法的计算效率,在求解单向稳态渗流的有限分析算法基础上,构建二维非均匀多孔介质中不可压两相渗流的有限分析算法.算法中,网格界面上的平均渗透率不是简单地取为相邻网格渗透率的调和平均值,而是通过奇点邻域解析解积分求得.相比于传统的数值算法,有限分析算法随着网格的加密,能够很快地收敛(仅需将原始网格细分至2×2或3×3),并且其计算精度和收敛性不依赖于介质的非均匀强度,从而计算效率得到提高.  相似文献   

11.
In this paper, a 3D algorithm for the treatment of radiative heat transfer in emitting, absorbing, and scattering media is developed. The numerical approach is based on the utilization of the unstructured control volume finite element method (CVFEM) which, to the knowledge of the authors, is applied for the first time to simulate radiative heat transfer in participated media confined in 3D complex geometries. This simulation makes simultaneously the use of the merits of both the finite element method and the control volume method. Unstructured 3D triangular element grids are employed in the spatial discretization and azimuthal discretization strategy is employed in the angular discretization. The general discretization equation is presented and solved by the conditioned conjugate gradient squared method (CCGS). In order to test the efficiency of the developed method, several 3D complex geometries including a hexahedral enclosure, a 3D equilateral triangular enclosure, a 3D L-shaped enclosure and 3D elliptical enclosure are examined. The results are compared with the exact solutions or published references and the accuracy obtained in each case is shown to be highly satisfactory. Moreover, this approach required a less CPU time and iterations compared with those of even parity formulation of the discrete ordinates method.  相似文献   

12.
Energy propagation in random viscoelastic media is considered in this Letter. The forced response of uncertain waveguide subject to time harmonic loading is treated. This energy model is based on a spectral approach called the “Stochastic Wave Finite Element” (SWFE) method which is detailed in this Letter. Assuming that the random properties are spatially homogeneous in the media, the SWFE is a hybridization of the deterministic wave finite element and a parametric probabilistic approach. The proposed model is applicable in a wide frequency band with reduced time consumption. Numerical examples show the effectiveness of the proposed approach to predict the statistics of kinematic and quadratic variables of guided wave propagation. The results are compared to Monte Carlo simulations.  相似文献   

13.
Algorithm and code are presented that solve dispersion equations for cylindrically layered media consisting of an arbitrary number of elastic and fluid layers. The algorithm is based on the spectral method which discretizes the underlying wave equations with the help of spectral differentiation matrices and solves the corresponding equations as a generalized eigenvalue problem. For a given frequency the eigenvalues correspond to the wave numbers of different modes. The advantage of this technique is that it is easy to implement, especially for cases where traditional root-finding methods are strongly limited or hard to realize, i.e., for attenuative, anisotropic, and poroelastic media. The application of the new approach is illustrated using models of an elastic cylinder and a fluid-filled tube. The dispersion curves so produced are in good agreement with analytical results, which confirms the accuracy of the method. Particle displacement profiles of the fundamental mode in a free solid cylinder are computed for a range of frequencies.  相似文献   

14.
This paper discusses the well-known, but often misunderstood, concept of complex modes of dynamic structures. It shows how complex modes can be interpreted in terms of wave propagation phenomena caused by either localized damping or propagation to the surrounding media. Numerical simulation results are presented for different kinds of structures exhibiting modal and wave propagation characteristics: straight beams, an L-shaped beam, and a three-dimensional frame structure. The input/output transfer relations of these structures are obtained using a spectral formulation known as the spectral element method (SEM). With this method, it is straightforward to use infinite elements, usually known as throw-off elements, to represent the propagation to infinity, which is a possible cause of modal complexity. With the SEM model, the exact dynamic behavior of structures can be investigated. The mode complexity of these structures is investigated. It is shown that mode complexity characterizes a behavior that is half-way between purely modal and purely propagative. A coefficient for quantifying mode complexity is introduced. The mode complexity coefficient consists of the correlation coefficient between the real and imaginary parts of the eigenvector, or of the operational deflection shape (ODS). It is shown that, far from discontinuities, this coefficient is zero in the case of pure wave propagation in which case the plot of the ODS in the complex plane is a perfect circle. In the other extreme situation, a finite structure without damping (or with proportional damping), where the mode shape (or the ODS) is a straight line on the complex plane, has a unitary complexity coefficient. For simple beam structures, it is shown that the mode complexity factor can also be calculated by curve-fitting the mode to an ellipse and computing the ratio of its radii.  相似文献   

15.
In waveguide structures, waves may be partially reflected by local non-uniformities such as cracks and other defects. The reflection and transmission characteristics associated with the presence of a discontinuity may be used, in principle, to give some indication of both the location and size of the defect. A combined spectral element and finite element (SE/FE) method has been used previously to investigate the effects of local non-uniformities at relatively low frequencies. However, for analysis at higher frequencies, where complex deformation of the waveguide occurs, it is necessary to extend this approach. Such high frequency analysis is necessary if small defects are to be located within the waveguide cross-section. In order to investigate wave propagation at higher frequencies, a combined spectral super element and finite element (SSE/FE) method is presented. This method allows the transmission, reflection and wave conversion at discontinuities to be determined for complex waveguides. As an example of the use of this method, wave reflection and transmission in rails are estimated at frequencies between 20 and 40 kHz for various notional sawcut-like defects of progressively increasing size. This shows the feasibility of the approach for realistic waveguides. However, from these simulations it is shown that defects have to be quite large before they can be detected using a single transducer position on the rail cross-section using train-induced vibration.  相似文献   

16.
Two absorbing boundary conditions, the absorbing sponge zone and the perfectly matched layer, are developed and implemented for the spectral difference method discretizing the Euler and Navier–Stokes equations on unstructured grids. The performance of both boundary conditions is evaluated and compared with the characteristic boundary condition for a variety of benchmark problems including vortex and acoustic wave propagations. The applications of the perfectly matched layer technique in the numerical simulations of unsteady problems with complex geometries are also presented to demonstrate its capability.  相似文献   

17.
Piezoelectric Kagome grids can be considered as a kind of functional material because they have vibration isolation performance and can transform mechanical energy to electric energy. In this study, the dynamic properties of three-dimensional (3D) piezoelectric Kagome grids without and with material defects are studied based on the frequency-domain responses. The spectral element method (SEM) is adopted to solve a 3D piezoelectric beam which contains bending components in two planes, tensional components, and torsional components. The dynamic stiffness matrix of a spectral piezoelectric beam is derived. Highly accurate solutions in the frequency-domain are obtained by solving the equation of motion of the whole structure. Compared with the results from the FEM and those in the existing literature, it can be seen that the SEM can be effectively used to study the 3D piezoelectric Kagome grids. The band-gap properties of Kagome grid and defect state properties of Kagome grid with material defects are analyzed. The effect of the piezoelectric parameter on the band-gap property is investigated further.  相似文献   

18.
A semi-analytical method based on distributed source transmission line model is proposed to analyze a traveling-wave terahertz photomixer integrated with a coplanar stripline waveguide. Multilayer spectral domain method along with complex image technique have been applied to calculate the distributed voltage source element in the transmission line representation. To find the coupled terahertz signal along the coplanar stripline, the transmission line equations are solved. The results obtained from the proposed method are verified by the full wave analysis.  相似文献   

19.
The aim of this paper is to introduce a new finite spectral element of a cracked Timoshenko beam for modal and elastic wave propagation analysis. The proposed approach deals with the spectral element method. This method is suitable for analyzing wave propagation problems as well as for calculating modal parameters of the structure. In the paper, the results of the change in modal parameters due to crack appearance are presented. The influence of the crack parameters, especially of the changing location of the crack, on the wave propagation is examined. Responses obtained at different points of the beam are presented. Proper analysis of these responses allows one to indicate the crack location in a very precise way. This fact is very promising for the future work in the damage detection field.  相似文献   

20.
We present an accurate and efficient generalized pseudospectral method for solving the time-dependent Schrödinger equation for atomic systems interacting with intense laser fields. In this method, the time propagation of the wave function is calculated using the well-known second-order split-operator method implemented by the numerically exact, fast transform between the grid and spectral representations. In the grid representation, the radial coordinate is discretized using the Coulomb wave discrete variable representation (CWDVR), and the angular dependence of the wave function is expanded in the Gauss-Legendre-Fourier grid. In the spectral representation, the wave function is expanded in terms of the eigenfunctions of the field-free zero-order Hamiltonian. Calculations on the high order harmonic generation and ionization dynamics of hydrogen atom in strong laser pulses are presented to demonstrate the accuracy and efficiency of the present method. This new algorithm will be found more computationally attractive than the close-coupled wave packet method using CWDVR and/or methods based on evenly spaced grids.  相似文献   

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