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1.
对于半无限域中波动散射问题的数值分析,人工边界条件的实现及波动输入是其中的关键问题之一。在波动输入的自由场分析中,以往研究大多考虑垂直入射或入射方向平行于含纵坐标轴的某一坐标面,难以真实地反映地震动的真三维效应,局限了其应用范围。论文文考虑空间任一角度入射的平面波,通过传递矩阵方法和坐标系变换,得到三维空间的自由场,结合集中质量显式有限元方法,实现了透射边界和粘弹性人工边界的波动输入以及三维波动散射的数值模拟,通过自编的程序及算例,验证了该方法的有效性,对比分析了空间入射角度对波动散射的影响。  相似文献   

2.
近场波动的数值模拟   总被引:39,自引:0,他引:39  
本文评述了近年来波源(或散射体)及其邻域内波动数值模拟的主要研究结果,着重讨论了人工边界条件这一关键问题的研究进展  相似文献   

3.
消除多次透射公式漂移失稳的措施   总被引:12,自引:0,他引:12  
周正华  廖振鹏 《力学学报》2001,33(4):550-554
基于对双曲型偏微分方程数值解稳定性的GKS(Gustafsson,Kreiss and Sundstroem)准则的一种物理解释,提出了在波动数值模拟中消除多次透射公式飘移失稳的一个简单措施,并用波源问题和散射问题的数值试验检验了这一措施在稳定实现多次透射公式中的有效性。  相似文献   

4.
局部人工边界稳定性的一种分析方法   总被引:9,自引:2,他引:9  
关慧敏  廖振鹏 《力学学报》1996,28(3):376-380
采用时域局部人工边界同有限元或有限差分相结合的方法分析无界域中的波动问题时可能出现由边界引起的数值失稳现象.本文提出一种分析局部人工边界稳定性的实用方法.该方法从时域逐步积分格式出发,考虑了边界节点运动和内部节点运动的耦合以及离散化的影响,可以给出局部人工边界在多维波动数值模拟中的稳定性近似准则.文中对多次透射边界在一维及二维出平面波动模拟中稳定性的分析结果,表明了该方法的合理性  相似文献   

5.
孔曦骏  邢浩洁  李鸿晶 《力学学报》2022,54(9):2513-2528
流固耦合地震波动问题主要研究由流体和固体构成的复杂系统中地震波传播特性及其规律. 传统模拟方法中一般以声波方程、弹性波方程的数值解分别描述理想流体和弹性固体中的波动, 并实时地处理两种不同性质介质之间的相互耦合作用, 数值格式复杂且限制数值模拟精度与计算效率. 本文采用谱元法结合多次透射公式人工边界条件实现了一种流固耦合地震波动问题的高阶显式数值计算方法. 该方法利用了流固耦合问题统一计算框架,可将饱和多孔介质的Biot波动方程分别退化为理想流体的声波方程和弹性固体的弹性波方程. 通过P波垂直入射的水平成层理想流体-饱和多孔介质-弹性固体场地模型、P波斜入射的不规则层状界面以及任意形状界面的理想流体-饱和多孔介质-弹性固体场地模型等三个算例, 与传递函数法解析解以及集中质量有限元法计算结果进行对比分析, 证明了本文方法的正确性与有效性. 数值模拟结果表明, 本文方法相较传统有限元法可以少得多的节点数量获得更高的数值精度, 并且在较宽的频率范围内都能可靠地模拟出流固耦合系统的动力响应, 充分体现出本文方法兼顾高精度、计算效率和复杂场地建模灵活的特点.   相似文献   

6.
波动数值模拟的一种显式方法——一维波动   总被引:2,自引:2,他引:0  
本文提出了波动时域数值模拟的一种新的显式方法,并通过一维非规则网格节点递推公式的建立说明此方法。为了阐明应用此法构建高精度、稳定递推公式的可行性,详细论述了一维均匀网格标量波动数值模拟的精度和稳定性;提出了构建时空精度皆为 阶( 为正整数)的稳定递推公式的技术途径,并以构建二阶(M=1)和四阶(M=2)公式为例予以说明。最后,通过算例详细说明了本文理论结果。  相似文献   

7.
黏弹流体流动的数值模拟研究进展   总被引:5,自引:1,他引:4  
综述了黏弹流体流动数值模拟的研究进展,突出介绍近十年来有限元法在黏弹流体流动数值模拟研究中取得的成果,通过动量方程的适当变形和本构方程离散权函数的合理选择,可以显著增强数值计算的稳定性。得到较高Weissenberg数下的解,同时文中对黏弹流体流动数值模拟中本构方程的应用、非等温情况和三维空间下的研究进行了介绍。  相似文献   

8.
陈苏  丁毅  孙浩  赵密  王进廷  李小军 《力学学报》2023,55(1):272-282
近年来,物理先验融合数据的深度学习方法求解以偏微分方程为理论基础的正反演问题已成为交叉学科热点.针对地震工程波动数值模拟,本文阐明了物理驱动深度学习方法 PINN的数学概念及实现方式,以无源项一维波动为例,开展了相关理论模型构建,并与解析解及有限差分方法进行对比,分析了PINN方法与其他数值算法模拟波场的相对范数误差,验证了物理驱动深度学习方法求解波动问题的可行性.采用物理驱动深度学习方法并结合谱元法形成的稀疏初始波场数据,开展了二维波动数值模拟,实现了自由边界条件及起伏地表等典型工况的模拟,并给出了时序波场分布特性.更换不同的初始条件,测试了神经网络的泛化精度,提出可显著提高网络训练效率的迁移学习方法.通过与谱元法的结果对比,验证了本文方法模拟均质场地、空间不均匀及复杂地形场地波动问题的可靠性.结果表明,物理驱动深度学习方法具备无网格、精细化模拟等优势,并可实现自由地表及侧边界波场透射等数值模拟条件.  相似文献   

9.
海洋内波是发生在密度分层海水中的波动,对潜艇航行的稳定性和悬停性都有重要影响。本文采用有限体积自适应半结构多重网格法求解Navier-Stokes方程,并用VOF(Volume of Fluid)方法追踪两层流体界面,应用双推板造波法进行内孤立波数值造波,对两层流体中的内孤立波数值造波方法进行研究和探讨。数值模拟结果证...  相似文献   

10.
结合考虑了吸收边界条件的有限元正演方法,通过离散切比雪夫多项式在特定离散点的展开逼近待识别函数,实现了无限区域内二维缺陷的识别。正问题计算中引入的吸收边界条件虽然不能严格地模拟无限域对近场波动的影响,但能够以满足实际需要的精度模拟这一影响,且具有解耦特性,极大地简化了数值计算,在反演计算中,离散点取在切比雪夫多项式的零点处,使逼近时最大偏差最小,数值算例表明此方法的有效性。  相似文献   

11.
The features of propagation of longitudinal and transverse waves (LW and TW) in fractured porous medium (FPM) saturated with liquid are investigated by methods of multiphase mechanics. The mathematical model of FPM accounting for inequality of velocities and pressures of liquid in pores and fractures, liquid mass exchange and nonstationary interaction forces is developed. Processes of monochromatic wave propagation are studied. The dispersion relation is obtained and the effect of model parameters on wave propagation is analysed. It is established that one transverse and three longitudinal waves propagate in FPM saturated with liquid. The fastest LW is a deformational wave and the two others are filtrational. Filtrational waves attenuate much stronger than deformational and transverse waves. Distinction of velocities and pressures in liquid in various pore systems provides an explanation for the existence of the two filtrational waves in porous medium with two different characteristic sizes of pores.  相似文献   

12.
This research addresses the investigation of an elastic wave field in a homogeneous and isotropic porous medium which is fully saturated by a Newtonian viscous fluid. A new methodology is developed for describing the wave field in the medium excited by multiple energy sources. To quantify the relative displacements between the fluid and solid of the medium, the governing equations of the elastic wave propagation are derived in the form of displacements specially. The velocities and attenuation of the waves are considered as functions of viscosity and frequency. Making use of the Hankel function and the moving-coordinate method, a model of the wave motion with multiple cylindrical wave sources is built. Making use of the model established in this research, the relative displacement between the fluid and the solid can be quantified, and the wave field in the porous media can then be determined with the given energy sources. Numerical simulations of cylindrical waves from multiple energy sources propagating in the porous medium saturated by viscous fluid are performed for demonstrating the practicability of the model developed.  相似文献   

13.
This paper studies the evolution of a wave pulse during propagation through a porous obstacle located in a gas and saturated with it. The cases of open and closed boundaries of the porous obstacle are considered. The effect of the parameters of the porous medium such as the initial value of the gas volume fraction and pore size and interfacial heat transfer on the evolution of the wave pulse was analyzed.  相似文献   

14.
移动荷载作用下饱和土地基中的波动特性分析   总被引:1,自引:1,他引:0  
孙波 《计算力学学报》2018,35(6):802-808
基于Biot波动方程,经过Fourier变换和逆Fourier变换后可获得波数-频率域以及时间-空间域的解析解。通过数值分析的手段研究了移动荷载作用下饱和多孔弹性地基中波的传播特性。重点就弥散曲线、多谱勒效应、波的成分和动力响应频率等几个特性进行了分析,发现饱和土地基由于比弹性地基多了一项流体介质,波动特性明显差异于弹性介质。  相似文献   

15.
16.
The problem of the propagation of longitudinal Biot waves in a porous medium saturated with a weakly compressible liquid (water) or a gas is considered theoretically. The frequency dependence of the phase velocities and damping coefficients is investigated numerically. It is shown that for a certain relationship between the parameters of the porous medium and the saturating fluid there is a “critical” frequency at which the properties of longitudinal waves of both kinds are identical. An analytical expression for this “critical” frequency is obtained. It is shown that for a gas-saturated porous medium, at a certain frequency, in both longitudinal waves the relative gas-matrix motion changes type. Assuming that the saturating-gas behavior corresponds to an adiabatic equation of state, an estimate is obtained for the threshold pore pressure necessary for the restructuring of the relative motion. The wave associated with matrix deformation is shown to have a high damping coefficient in a porous medium saturated with a weakly compressible liquid (water in the case considered) but to be only weakly damped in a gas-saturated porous medium.  相似文献   

17.
The propagation of nonlinear waves through a porous medium saturated with a viscous liquid and a gas is investigated with allowance for the capillary pressure. Numerical solutions of the traveling-wave type are constructed for the generalized Korteweg-de Vries-Burgers equation for the wave amplitudes. Three types of regimes of longitudinal wave propagation, including soliton-like regimes, are found.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 86–95, July–August, 1996.  相似文献   

18.
基于饱和多孔介质理论,在固相和液相微观不可压,固相骨架小变形且满足线性粘弹性积分型本构关系的假定下,建立了流体饱和粘弹性多孔介质动力响应的若干Gurtin型变分原理,包括Hu-Washizu变分原理.利用所建立的变分原理,导出了流体饱和粘弹性多孔介质动力响应无网格数值模拟的离散控制方程,此方程是一个关于时间的对称微分方程组,便于分析计算.作为数值例子,研究了流体饱和粘弹性多孔柱体的一维动力响应,数值结果揭示了流体饱和粘弹性多孔柱体中波的传播特性以及固相粘性的影响.  相似文献   

19.
The propagation of elastic waves is studied in a porous solid saturated with two immiscible viscous fluids.The propagation of three longitudinal waves is represented through three scalar potential functions.The lone transverse wave is presented by a vector potential function.The displacements of particles in different phases of the aggregate are defined in terms of these potential functions.It is shown that there exist three longitudinal waves and one transverse wave.The phenomena of reflection and refraction due to longitudinal and transverse waves at a plane interface between an elastic solid half-space and a porous solid half-space saturated with two immiscible viscous fluids are investigated.For the presence of viscosity in pore-fluids,the waves refracted to the porous medium attenuate in the direction normal to the interface.The ratios of the amplitudes of the reflected and refracted waves to that of the incident wave are calculated as a nonsingular system of linear algebraic equations.These amplitude ratios are used to further calculate the shares of different scattered waves in the energy of the incident wave.The modulus of the amplitude and the energy ratios with the angle of incidence are computed for a particular numerical model.The conservation of the energy across the interface is verified.The effects of variations in non-wet saturation of pores and frequencies on the energy partition are depicted graphically and discussed.  相似文献   

20.
Evolution of a moderate-intensity shock wave and its enhancement after reflection from a rigid surface embedded in a porous medium are studied experimentally. The medium is saturated with a liquid that has bubbles of a soluble gas. A physical mechanism of shock wave enhancement in a saturated porous medium is proposed. Experimental data on the amplitude and velocity of reflected waves are compared with results of theoretical modeling. The process of gas bubble dissolution behind a shock wave is studied.  相似文献   

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