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41.
海啸的数值模拟是海啸研究的一个重要领域, 它对于帮助理解海啸的基本物理特性和预防减灾具有重要意义。 海啸数值模拟程序的编制是一项繁杂的工作, 该文介绍了利用两种功能强大的通用软件(PETSc和FEPG)来进行海啸数值模拟程序编写的研究。 PETSc和FEPG采用有限差分、 有限元、 有限体积等多种离散方法, 可以对数值问题给出稳定的求解。 该文采用了直角坐标系下的非线性浅水波方程作为海啸波传播的控制方程进行离散求解, 并将其结果与TUNAMI N1模型进行了比较, 表明这两种方法方便而且有效。 相似文献
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上海市曾遭受了严重的地面沉降灾害,主要由于浅部含水层开采引发浅部土层固结所致。之后采取了回灌浅部含水层并转向开采深部含水层的措施,地面沉降得到了有效控制。但21世纪初,通过水位及分层沉降监测,发现随着开采量增加,深部含水层也会成为主要压密土层。其变形呈现出显著的非线性压密特征,即使水位普遍抬升,压密仍然持续,开展其固结压密机理模型研究对地面沉降防治十分必要。传统太沙基理论认为砂土骨架是瞬时变形的,忽略了流变性本质,因此无法解释该现象。基于国内外学者的研究,考虑了前期固结压力前后流变性的差异,建立了深部含水层黏弹塑固结压密模型。通过试验获取了相关参数,结合塘桥F16分层标监测结果,对第四含水层长期压密变形进行了模拟。模拟结果很好地反映了含水层长期非线性压密行为,研究结果对指导防治地面沉降有实际意义。 相似文献
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Dynamic response of a pile considering the interaction of pile variable cross section with the surrounding layered soil 下载免费PDF全文
Assuming that the pile variable cross section interacts with the surrounding soil in the same way as the pile toe does with the bearing stratus, the interaction of pile variable cross section with the surrounding soil is represented by a Voigt model, which consists of a spring and a damper connected in parallel, and the spring constant and damper coefficient are derived. Thus, a more rigid pile–soil interaction model is proposed. The surrounding soil layers are modeled as axisymmetric continuum in which its vertical displacements are taken into account and the pile is assumed to be a Rayleigh–Love rod with material damping. Allowing for soil properties and pile defects, the pile–soil system is divided into several layers. By means of Laplace transform, the governing equations of soil layers are solved in frequency domain, and a new relationship linking the impedance functions at the variable‐section interface between the adjacent pile segments is derived using a Heaviside step function, which is called amended impedance function transfer method. On this basis, the impedance function at pile top is derived by amended impedance function transfer method proposed in this paper. Then, the velocity response at pile top can be obtained by means of inverse Fourier transform and convolution theorem. The effects of pile–soil system parameters are studied, and some conclusions are proposed. Then, an engineering example is given to confirm the rationality of the solution proposed in this paper. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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An approach is developed to simulate wave–wave interactions using nonlinear elliptic mild-slope equation in domains where wave reflection, refraction, diffraction and breaking effects must also be considered. This involves the construction of an efficient solution procedure including effective boundary treatment, modification of the nonlinear equation to resolve convergence issues, and validation of the overall approach. For solving the second-order boundary-value problem, the Alternating Direction Implicit (ADI) scheme is employed, and the use of approximate boundary conditions is supplemented, for improved accuracy, with internal wave generation method and dissipative sponge layers. The performance of the nonlinear model is investigated for a range of practical wave conditions involving reflection, diffraction and shoaling in the presence of nonlinear wave–wave interactions. In addition, the transformation of a wave spectrum due to nonlinear shoaling and breaking, and nonlinear resonance inside a rectangular harbor are simulated. Numerical calculations are compared with the results from other relevant nonlinear models and experimental data available in literature. Results show that the approach developed here performs reasonably well, and has thus improved the applicability of this class of wave transformation models. 相似文献
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现有天线曲面拟合算法均基于最小二乘法,难以消除多个粗差对拟合结果的影响。本文基于等价权抗差估计思想,利用线性规划计算残差初值,再进行选权迭代计算。通过算例,证明本文方法能较好地探查多个粗差,且计算结果精度更高。 相似文献
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The initiation and propagation of directional hydraulic fracturing (DHF) was investigated based on true tri-axial experiment and finite element modeling. The influences of notch angle, notch length and injection rate on the DHF were investigated. The initiation and propagation of DHF was modeled by a 3D nonlinear finite element method. A comparison between experimental investigation and numerical modeling results indicates that there is a good correlation between unbalanced force (UF) and fracturing. UF can be used to predict the hydraulic fracture initiation and propagation. 相似文献
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多视SAR影像像素强度通常建模为Gamma分布,其形状参数为常数(视数)。实验表明,多视SAR影像分割时,设Gamma分布的形状参数为变量可取得更好的分割结果。由于Gamma分布中形状参数以Gamma函数的形式出现,利用EM算法求解时无法获得形状参数的解析解。为此,本文提出了一种基于Expectation/Conditional Maxinnization(ECM)算法的多视SAR影像分割方法。利用ECM算法估计最大化后验概率条件下的Gamma分布参数及表征最优多视SAR影像分割的标号场实现。采用模拟和真实多视SAR影像验证提出算法。实验结果表明,Gamma分布的形状和尺度参数均能快速收敛到稳态值,且以此得到各同质区域的Gamma分布曲线可以很好地拟合其直方图。通过对分割结果的定性和定量分析,可知提出算法具有有效性和可行性,且优于EM算法。 相似文献