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71.
72.
多次透射公式的一种高频失稳机制 总被引:2,自引:3,他引:2
本文利用一维双曲型偏微分方程组初边值问题数值稳定性的GKS定理的物理解释和推广,分析了多次透射公式在数值实现中可能出现的一种高频失稳机制,即在多维离散网格,沿某一空间方向的外行简谐波,由于与其他空间方向节点运动的耦合效应可以使能量传播方向反向。文中通过数值试验对这一失稳机制作了初步验证。 相似文献
73.
连续测量岩心的流动电势效应和电渗效应,可以获得岩心的动电渗透率,并验证Onsager互易性.通常这两个实验的岩心夹持器需要使用不同的堵头,而更换堵头会导致岩心内流体的参数和边界条件发生变化.本文设计了新的岩心夹持器和激励压力源,避免了在测量过程中更换堵头,提高了两个实验的一致性.本文测量了蒸馏水、以及0.01、0.02、0.05、0.1、0.2、0.4和0.6mol/L氯化钠溶液饱和的10块岩心的流动电势效应和电渗效应,获得了动电渗透率,并验证了低矿化度下的Onsager互易性.结果表明,Onsager互易性在低矿化度下是成立的;对于高矿化度,电渗效应能够取代流动电势效应用于反演渗透率. 相似文献
74.
In this paper, a formulation for shakedown analysis of elastic-plastic offshore structures under cyclic wave loading is presented. In this formulation, a fast numerical solution method is used, suitable for the Finite Element Method (FEM) analysis of large offshore structures on which shear effects in addition to bending and axial effects are taken into account. The Morison equation is adopted for converting the velocity and acceleration terms into resultant forces and it is extended to consider arbitrary orientations of the structural members. The theoretical methods of the shakedown analysis are discussed in detail and the formulation is applied to an offshore structure to verify the concept employed and its analytical capabilities. 相似文献
75.
Massimiliano Guzzo 《Celestial Mechanics and Dynamical Astronomy》2002,83(1-4):303-323
We describe a numerical application of the Nekhoroshev theorem to investigate the long-term stability of quasi-integrable systems. We extend the results of a previous paper to a class of degenerate systems, which are typical in celestial mechanics. 相似文献
76.
Seyyed M. Hasheminejad Reza Avazmohammadi 《Soil Dynamics and Earthquake Engineering》2007,27(1):29-41
This study investigates the dynamic interaction of time harmonic plane waves with a pair of parallel circular cylindrical cavities of infinite length buried in a boundless porous elastic fluid-saturated medium. The novel features of Biot dynamic theory of poroelasticity along with the appropriate wave field expansions, the pertinent boundary conditions, and the translational addition theorems for cylindrical wave functions are employed to develop a closed-form solution in the form of infinite series. The analytical results are illustrated with numerical examples in which two empty cavities are insonified by a fast compressional or a shear wave at end-on incidence. The basic dynamic field quantities such as the hoop stress amplitude and the radial displacement of the elastic frame are evaluated and discussed for representative values of the parameters characterizing the system. The effects of the proximity of the two cavities, the incident wave frequency and type are examined. Particular attention has been focused on multiple scattering interactions in addition to the slow wave coupling effects which is known to be the primary distinction of the scattering phenomenon in poroelasticity from the classical elastic case. Limiting case involving two empty cylindrical cavities in an elastic solid is considered and excellent agreement with a well-known solution is established. 相似文献
77.
78.
Dimensions of shales and other geologic bodies that affect fluid flow through reservoirs and aquifers are often estimated from analogous deposits exposed in outcrops. Shale lengths observed in outcrops are biased because the finite length of outcrops truncates longer shales and long shales tend to be overrepresented in the sample. Shale length distributions can be modeled using an Erlangian probability density function based on termination frequency. Termination frequency can be calculated from outcrop observations even if the shales are incompletely exposed. Termination frequency is unbiased regardless of underlying shale length distribution and outcrop size and shape. Complex length distributions can be represented by a weighted sum of Erlangian models, each with a distinct termination frequency. The proportions and termination frequencies of the component models can be estimated using Bayes' theorem. Subsamples of the outcrop area can be analyzed to quantify spatial trends in termination frequency and thus shale length. These methods can be applied to estimate length distributions of any geologic object exposed in outcrops or other spatially limited samples. In many cases estimated termination frequency is normally distributed, and its variance can be estimated using closed-form expressions. Shale length distributions for the Frewens Sandstone were modeled using one- and two-component Erlangian probability density functions. The Frewens Sandstone is a tide-influenced deltaic sandstone body within the Cretaceous-age Frontier Formation, exposed in central Wyoming, USA. Length observations and Erlangian models agree reasonably well. Because the models correct for the effects of shale truncation in limited outcrop exposures, predicted means and proportions of long shales are substantially greater than observed values. There is a vertical trend and pronounced vertical cyclicity in termination frequency, indicating that shales become shorter upward and intervals of longer and shorter shales alternate. Along strike, termination frequency decreases away from the sandstone-body axis, reflecting greater preserved shale lengths toward sandstone-body margins. No correlation was observed between distance along dip and termination frequency. Termination frequencies and histograms of shale length for adjacent, perpendicular walls are similar, indicating that there is no anisotropy in shale length. 相似文献
79.
G-S变换的快速算法 总被引:18,自引:8,他引:10
在电磁场瞬变响应的数值计算中 ,常采用G S变换法作逆拉氏变换 .它是纯实数运算 ,而且只需对较少的拉氏变换变量s值作计算 (通常对每一采样时间选用 1 2个s值 ) ,因而是一种计算速度较快的算法 .但是 ,要对大量采样时间作计算 ,其计算量仍太大 .本文基于拉氏变换的延迟定理 ,建立了一种新的G S变换算法 .数值检验结果表明 ,新算法可成级次地减少对大量采样时间作G S变换的计算量 ,显著提高电磁场瞬变响应的计算速度 . 相似文献
80.