共查询到20条相似文献，搜索用时 140 毫秒
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运用BP网络附加动量法和自适应学习速率法，建立神经网络模型，模拟计算涌潮波速。根据部分试验数据对网络进行训练，确定相关参数，建立涌潮波速计算模型，同时利用其余部分试验数据对模型进行检验，模拟结果与试验数据吻合较好，相关程度高，表明神经网络模型用于计算涌潮波速是合适的。 相似文献
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本文利用TerraSAR-X(TSX)卫星于2010年4月22日在南海东沙岛附近海域获取的数据进行海洋内孤立波动力要素和海表流速信息的提取研究。基于TSX数据的后向散射强度信息,利用经验模态分解法得到内孤立波半波宽度,再利用两层模型法和参数化法计算得到内孤立波振幅和相速度。反演结果显示,利用参数化方法得到的振幅(约21~39 m)和两层模型法得到的相速度(约1.07 m/s)与历史实测资料较为一致。进而利用TSX的顺轨干涉数据获取研究海域内的多普勒速度,再分别采用M4S模型法和直接分离法处理,进而提取海表流速。结果显示,两种方法得到的海表流速的全场平均值较为一致,均为1.10 m/s左右。M4S模型法对流速最大值的改变量较大而直接分离法对流速最小值的改变量较大。M4S模型对内孤立波波峰线区域海表流速的修正大于无内孤立波的海域。最后,基于KdV方程计算得到内孤立波引起的表面流的流速约为0.28 m/s,对反演出的海表流速贡献占比23%。 相似文献
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本文通过对福建及其周边地区地震活动人工神经网络模型的构建,研究了人工神经网络方法在基于该区域地震活动性指标的地震分析预报中的应用。选用含一个中章层的前向神经网络模型,并采用与之相适应的ＢＰ算法,以该地区１９７１～１９９７年的地震活动性资料为基础,用神经网络进行实际计算、分析和检验。结果表明：神经网络模型对福建及其周边地区地震震级的预测检验效果较好的,可以在一定精度范围内使震级预测的内符率达１００％ 相似文献
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采用理论研究和试验研究相结合的方法,对两层流体中内孤立波对不同水深竖直圆柱体水平作用力进行了分析。采用重力塌陷法进行内孤立波造波试验,通过PIV(Particle Image Velocimetry)技术获取内孤立波波剖面的时间序列,利用测力系统对竖直圆柱体在内孤立波作用下的受力进行测量。通过内孤立波波剖面试验分析,选取合适的内孤立波理论并对竖直圆柱体所受内孤立波作用力进行计算,将计算结果与试验结果进行汇总分析。结果表明:上层流体中圆柱体所受内孤立波最大水平作用力明显大于下层流体中各段圆柱体,且方向相反;随着内孤立波振幅的增大,各段圆柱体所受内孤立波最大水平作用力也相应地增大;密度跃层处圆柱体所受水平作用力具有相较于其他位置处更为复杂的变化趋势;选用合适的内孤立波理论进行计算能够较好的模拟竖直圆柱体的实际水平受力。 相似文献
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用ｆＫｄＶ模式方程对单层二维表面波进行直接的数值研究。计算得出，在共振区域先锋孤立子的生成与Ｔ、Ｙ．Ｗｕ（吴耀祖）及Ｓ．Ｊ．Ｌｅｅ等人的结果相同。在共振点与超临界转向点之间，对每一个Ｆｒ数存在初始不稳定的单峰孤立子，其振幅随时间增加。当Ｆｒ数接近共振区时，初始孤立子分裂成先峰孤立子，即先峰孤立子生成是占优的。当Ｆｒ接近超临界转向点时，这类初始不稳定孤立子最终破碎。当Ｆｒ超过超临界转向点时，存在一类稳定的超临界孤立子，其振幅不随时间变化，但是它得自时间相关方程。这类孤立子位于驱动力上方，它的振幅随Ｆｒ的增加而减少．由于它不同于自由ＫｄＶ孤立子，因此本文称之为超临界驻定孤立子。 相似文献
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基于神经网络的平底结构砰击压力预报 总被引：1，自引：0，他引：1
对利用神经网络预报平底结构入水砰击压力的方法进行了探讨。首先利用仿真软件计算各种情况下平底结构入水所产生的砰击压力，以此形成训练神经网络的数据集。其次利用数据集对三层反馈式网络进行了训练，讨论了不同隐含层节点数对该非线性系统的拟合能力，并且对梯度下降法、动量修正法和基于优化的LM算法的有效性和精度进行了比较，最后得出了适合平底结构入水砰击系统的网络结构。 相似文献
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Vegetation damping effects on propagating water waves have been investigated by many researchers. This paper investigates the effects of damping due to vegetation on solitary water wave run-up via numerical simulation. The numerical model is based on an implementation of Morison's formulation for vegetation induced inertia and drag stresses in the nonlinear shallow water equations. The numerical model is solved via a finite volume method on a Cartesian cut cell mesh. The accuracy of the numerical scheme and the effects of the vegetation terms in the present model are validated by comparison with experiment results. The model is then applied to simulate a solitary wave propagating on a plane slope with vegetation. The sensitivity of solitary wave run-up to plant height, diameter and stem density is investigated by comparison of the numerical results for different patterns of vegetation. The numerical results show that vegetation can effectively reduce solitary wave propagation velocity and that solitary wave run-up is decreased with increase of plant height in water and also diameter and stem density. 相似文献
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近岸植被对波浪爬坡具有一定的衰减作用。在自然界中,由于植被的死亡、再生或人为破坏等原因,近岸植被通常呈片状分布,且其内部分布也是不均匀的。本文以完全非线性Boussinesq方程为基础,引入植被作用项,建立了模拟近岸植被区波浪传播的数值模型,验证了模型可靠性,进而采用该模型模拟分析了片状分布植被对孤立波爬高的影响。数值模拟结果表明,片状分布植被能有效减小孤立波爬高;对于均匀分布的片状植被,高密度片状植被对孤立波爬高的消减效果优于低密度片状植被;对于相同密度、不同分布形式的片状植被,均匀分布的片状植被对孤立波的消减效果优于不均匀分布的片状植被;对于不均匀分布的片状植被,前密后疏的片状植被对孤立波的消减效果优于前疏后密的片状植被。 相似文献
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The boundary integral equation method (BIEM) is developed as a tool for studying two-dimensional, nonlinear water wave problems, including the phenomena of wave generation, propagation and run-up. The wave motions are described by a potential flow theory. Nonlinear free-surface boundary conditions are incorporated in the numerical formulation. Examples are given for either a solitary wave or two successive solitary waves. Special treatment is developed to trace the run-up and run-down along a shoreline. The accuracy of the present scheme is verified by comparing numerical results with experimental data of maximum run-up. 相似文献
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The run-up and back-wash processes of single and double solitary waves on a slope were studied experimentally. Experiments were conducted in three different wave flumes with four different slopes. For single solitary wave, new experimental data were acquired and, based on the theoretical breaking criterion, a new surf parameter specifically for breaking solitary waves was proposed. An equation to estimate maximum fractional run-up height on a given slope was also proposed. For double solitary waves, new experiments were performed by using two successive solitary waves with equal wave heights; these waves were separated by various durations. The run-up heights of the second wave were found to vary with respect to the separation time. Particle image velocimetry measurements revealed that the intensity of the back-wash flow generated by the first wave strongly affected the run-up height of the second wave. Showing trends similar to that of the second wave run-up heights, both the back-wash breaking process of the first wave and the reflected waves were strongly affected by the wave–wave interaction. Empirical run-up formula for the second solitary wave was also introduced. 相似文献
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This paper presents new laboratory experiments carried out in a supertank (300 m × 5 m × 5.2 m) of breaking solitary waves evolution on a 1:60 plane beach. The measured data are employed to re-examine existing formulae that include breaking criterion, amplitude evolution and run-up height. The properties of shoreline motion, underwater particle velocity and scale effect on run-up height are briefly discussed. Based on our analyses, it is evidently found that there exist five zones during a wave amplitude evolution course on the present mild slope. A simple formula which is capable of predicting maximum run-up height for a breaking solitary wave on a uniform beach with a wide range of beach slope (1:15–1:60) is also proposed. The calculated results from the present model agree favorably with available laboratory data, indicating that our method is compatible with other predictive models. 相似文献
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Solitary waves have been commonly used as an initial condition in the experimental and numerical modelling of tsunamis for decades. However, the main component of a tsunami waves acts at completely different spatial and temporal scales than solitary waves. Thus, use of solitary waves as approximation of a tsunami wave may not yield realistic model results, especially in the coastal region where the shoaling effect restrains the development of the tsunami wave. Alternatively, N-shaped waves may be used to give a more realistic approximation of the tsunami wave profile. Based on the superposition of the sech2(*) waves, the observed tsunami wave profile could be approximated with the N-shaped wave method, and this paper presents numerical simulation results based on the tsunami-like wave generated based on the observed tsunami wave profile measured in the Tohoku tsunami. This tsunami-like wave was numerically generated with an internal wave source method based on the two-phase incompressible flow model with a Volume of Fluid (VOF) method to capture the free surface, and a finite volume scheme was used to solve all the governing equations. The model is first validated for the case of a solitary wave propagating within a straight channel, by comparing its analytical solutions to model results. Further, model comparisons between the solitary and tsunami-like wave are then made for (a) the simulation of wave run-up on shore and (b) wave transport over breakwater. Comparisons show that use of these largely different waveform shapes as inputs produces significant differences in overall wave evolution, hydrodynamic load characteristics as well as velocity and vortex fields. Further, it was found that the solitary wave uses underestimated the total energy and hence underestimated the run-up distance. 相似文献
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I. I. Didenkulova A. A. Kurkin E. N. Pelinovsky 《Izvestiya Atmospheric and Oceanic Physics》2007,43(3):384-390
The problem of sea-wave run-up on a beach is discussed within the framework of exact solutions of a nonlinear theory of shallow water. Previously, the run-up of solitary waves with different forms (Gaussian and Lorentzian pulses, a soliton, special-form pulses) has already been considered in the literature within the framework of the same theory. Depending on the form of the incident wave, different formulas were obtained for the height of wave run-up on a beach. A new point of this study is the proof of the universality of the formula for the maximum height of run-up of a solitary wave on a beach for the corresponding physical choice of the determining parameters of the incident wave, so that the effect of difference in form is eliminated. As a result, an analytical formula suitable for applications, in particular, in problems related to tsunamis, has been proposed for the height of run-up of a solitary wave on a beach. 相似文献
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This paper considers the numerical simulation of nonlinear wave run-up within a highly accurate Boussinesq-type model. Moving wet–dry boundary algorithms based on so-called extrapolating boundary techniques are utilized, and a new variant of this approach is proposed in two horizontal dimensions. As validation, computed results involving the nonlinear run-up of periodic as well as transient waves on a sloping beach are considered in a single horizontal dimension, demonstrating excellent agreement with analytical solutions for both the free surface and horizontal velocity. In two horizontal dimensions cases involving long wave resonance in a parabolic basin, solitary wave evolution in a triangular channel, and solitary wave run-up on a circular conical island are considered. In each case the computed results compare well against available analytical solutions or experimental measurements. The ability to accurately simulate a moving wet–dry boundary is of considerable practical importance within coastal engineering, and the extension described in this work significantly improves the nearshore versatility of the present high-order Boussinesq approach. 相似文献
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孤立波与带窄缝双箱相互作用模拟研究 总被引：1，自引：1，他引：0
针对孤立波与带窄缝双箱的作用问题,应用时域高阶边界元方法建立了二维数值水槽。其中,自由水面满足完全非线性运动学和动力学边界条件,对瞬时自由表面流体质点采用混合欧拉-拉格朗日法追踪,采用四阶龙格库塔法对下一时刻的自由水面的速度势和波面升高进行更新。采用加速度势法求解物体湿表面的瞬时波浪力。采用推板方法生成孤立波。通过模拟孤立波在直墙上的爬高以及施加在直墙上的波浪力,并与已发表的实验和数值结果对比,验证本数值模型的准确性。通过数值模拟计算研究了窄缝宽度、方箱尺寸对波浪在箱体迎浪侧爬高,窄缝内波面升高,箱体背浪侧透射波高及箱体受波浪荷载的影响。同时研究了有一定时间间隔的双孤立波与带窄缝双箱系统作用问题。 相似文献
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波浪爬高是海岸工程中重要的水动力学问题之一,其数值模拟方法通常是通过离散Navier-Stokes方程或Boussinesq方程实现的,其中基于光滑粒子流体动力学方法是近年发展起来的。本文应用该方法模拟相同水深下,不同波高的孤立波在45(°)陡坡上的爬高,模拟结果与理论计算结果及已有物理模型试验结果进行了对比,并模拟出孤立波激散破碎过程及粒子分布和速度场的变化过程。结果表明,对密度近似方程进行重新初始化保持了流场内的质量守恒,同时整个计算域内的压力分布更加规则,说明光滑粒子流体动力学法在波浪爬高计算中的有效性。 相似文献