共查询到17条相似文献,搜索用时 640 毫秒
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谢圣朝谢久安唐铁生 《中国石油和化工标准与质量》2014,(10):263-263
波动方程描述了波的传播过程,其非线性特征使得求解过程极为复杂且计算量很大。通过数值模拟刻画波场传播十分重要。常见数值模拟方法有两类,分别是基于射线的方法和基于波动方程的方法。有限差分正演模拟是基于波动方程的正演方法。本文实现了高阶精度交错网格有限差分正演模拟,同时添加了完全匹配层(PML)吸收边界条件。计算结果表明,高阶精度交错网格有限差分数值模拟能有效抑制频散,PML吸收边界对边界的压制效果良好,几乎没有边界反射波。 相似文献
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井间地震以其高精度和高分辨率的显著特点在石油和天然气的勘探和开发中发挥着越来越重要的作用。本文根据各向同性介质中的一阶速度—应力弹性波方程,构造出了此方程在交错网格中的高阶有限差分格式以及它的稳定性条件,研究了该方程的完全匹配层(PML)吸收边界条件,在此基础上实现井间地震正演模拟,得到了高精度的地震合成记录。结果表明:井间地震可以观测到地震勘探中可能遇到的多种波场,利用数值模拟可以获得令人满意的合成地震记录。 相似文献
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《内蒙古石油化工》2015,(13)
通常采用高阶交错网格有限差分法求解一阶双曲型弹性波动方程或用伪谱法求解二阶弹性波动方程以提高局部弹性波场的数值模拟精度,这两种方法尽管能够有效压制频散现象和允许较大的空间步长,但占用的内存较多和计算量较大,而采用低阶中心差分法来求解,不可避免地存在着高频散问题,同时还带来计算过程不稳定现象,为此,提出了采用高阶交错网格有限差分法直接求解二阶弹性波动方程的新思路,推导的高阶差分格式具有计算形式简单,可以推广于求解任意偶数阶时空导数,同时给出计算所需的稳定性条件。在人工边界处采用褶积近似完全匹配层吸收边界条件(CAPML)来吸收衰减边界反射波。从梯状模型的数值结果可以看出,模拟的各种复杂波场清晰准确、精度较高、边界吸收效果好且计算过程稳定,同时指出,比常规方法具有更快速提高数值模拟精度和计算效率的优点。 相似文献
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《化工设计通讯》2021,(4)
地震波场的正演模拟不仅是地球物理勘探的重要组成部分,也是对地震资料进行分析处理的基础。其中波动方程求解法是一种重要的方法,该方法能反映地震波传播的动力学与运动学。在求解波动方程的所有方法中,有限差分法由于其速度快,精度高以及内存占用小,得到了广泛的利用。有限差分法主要将模型区域离散成有限个网格,然后在时间维度上,通过采样时间进行离散。再利用差分近似微分的求解方法,对微分形式的波动方程进行计算。最后给定一个初始条件,利用地震波在空间与时间上的变化,模拟地震波的传播。但是,传统的有限差分方法将模型等分成数个矩形网格,误差较大。因此,利用交错网格进行计算,能够较大地减少误差。以波动方程为基础,利用交错网格进行正演模拟,并与常规网格进行比较。模拟结果证明了交错网格的精度更高,可靠性更强。 相似文献
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运用Lamb波对复杂结构进行结构健康监测时,经常需要对Lamb波传播过程进行有限元仿真,但由于建模大小、复合材料各向异性等原因,会产生较多的边界反射波,从而掩盖损伤波形,因此建立吸收边界抑制反射波的影响就显得尤为重要。使用加入弹簧阻尼器Combin14单元的吸波边界,研究了吸波边界长度、频率、Combin14单元方向等对该吸收边界吸波效果的影响,并通过与传统的阻尼递增吸收边界进行对比,发现频率和吸波边界长度对弹簧阻尼器吸波边界吸波效果均无过大影响,但其吸波边界长度必须大于λ(波长)才会达到最优效果;当Combin14单元设置在沿传播方向时的吸波效果最好;相较于阻尼递增吸波边界,弹簧阻尼器吸波边界的仿真耗时明显减少且在低频段的吸波效果更好。 相似文献
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In this study, an improved mathematical model is presented to investigate the stress wave propagation in two circular cylinders bonded with a functionally graded adhesive layer. In the proposed model, the spatial derivatives of mechanical properties are included in the governing equations of the wave propagation. Also, the finite-difference method was used for the solution of the governing equations and boundary conditions. The Mori-Tanaka homogenization scheme was employed to evaluate the through-thickness mechanical properties of the adhesive layer. The effects of the spatial derivatives of the local mechanical properties and the through-thickness material composition variation in the adhesive layer were examined in detail. The presence of the material spatial derivatives in the governing equations mitigated the stress and displacement levels as well as axial and radial wave speeds. 相似文献
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本文提出了一种基于波动方程理论的合成震源记录逆时偏移方法,从双程无反射波动方程出发,实现了声波在数值空间的逆时延拓。提出了两种适用于逆时偏移的成像条件:零时刻成像条件和互相关成像条件,并在互相关成像条件的基础上就速度变化界面的低频假象问题提出了一种改进的成像条件:Pothyn Vector成像条件,文中所给模型的试算结果进一步说明了这三种成像条件的有效性和实用性。 相似文献
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为准确预测附加空气层的多层墙体内的温湿度分布和动态变化,研究多孔介质墙体内的热湿耦合非稳态传递规律,基于Luikov、Fick定律等基础传递理论,推导出热湿空气在墙体内部的瞬态耦合传递控制方程。通过对控制方程驱动势、方程项系数的改进,以空气含湿量和温度为驱动势,建立了建筑多孔介质墙体热湿耦合传递非稳态模型。采用有限容积法隐式差分格式设计了MATLAB模拟计算程序,设置相应的初始条件和边界条件,计算附加空气层的多层墙体内温度、湿度、传热和传湿量随时间变化的分布规律。最后,通过对比新建模型模拟结果与WUFI软件的模拟计算结果,验证了模型的准确性和可行性。 相似文献
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Experimental data on acoustic wave propagation through oil shale, summarized in a previous paper1, were used to develop a semi-empirical model. This model predicts the variation of pressure, effective compressional wave velocity, effective density and acoustic impedance with depth for a modified in-situ oil shale retort. Results from computer simulation of a variety of retort conditions establish the possibility of employing seismic propagation and reflection techniques for mapping of pyrolysis fronts in in-situ oil shale process beds. Such techniques are potentially free from uncertainties associated with proximate sensing of temperature profiles in these beds. 相似文献
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Nélio Henderson Eline Flores Marcelo Sampaio Léa Freitas Gustavo M. Platt 《Chemical engineering science》2005,60(7):1797-1808
The present work aims the modeling and simulation of supercritical fluid flow through porous media. This type of flow appears in several situations of interest in applied science and engineering, as the supercritical flow in porous materials employed in chromatography, supercritical extraction and petroleum reservoirs. The fluid is constituted of one pure substance, the flow is monophasic, highly compressible and isothermal. The porous media is isotropic, possibly heterogeneous, with rectangular format and the flow is two-dimensional. The heterogeneities of porous media are modeled by a simple power law, which describes the relationship between permeability and porosity. The modeling of the hydrodynamic phenomena incorporates the Darcy's law and the equation of mass conservation. Appropriated correlations are used to model, in a realistic form, the density and the viscosity of the fluid. A conservative finite-difference scheme is used in the discretization of the differential equations. The nonlinearity is treated by Newton method, together with the conjugate gradient method. The results of the simulation for pressure and mobility of supercritical and liquid propane flowing through porous media are presented, analyzed and graphically depicted. 相似文献
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《Polymer-Plastics Technology and Engineering》2013,52(1):91-102
Computer simulation packages have been successful in predicting filling behavior in extremely complicated geometries, and most of the current numerical solutions are based on a hybrid finite-element/finite-difference scheme and the middle-plane model. This imported model causes some inconvenience during applications. This study introduces surface model as the datum plane, instead of the traditional middle-plane model and additional boundary conditions in the gapwise direction are employed to keep the flows in the surfaces at the same section coordinative. The simulation presented here is compared with the experimental results obtained with instrumented test mold and C-Mold results. It is demonstrated that the present formulation is well suited to handle cavities generated directly by mold design process with computer aided design (CAD) tools. 相似文献