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1.
Numerical investigation of infragravity wave amplifications during harbor oscillations influenced by variable offshore topography 总被引：1，自引：1，他引：0
The infragravity (IG) period oscillations inside an elongated rectangular harbor near the offshore fringing reef induced by normal-incident bichromatic short wave groups are simulated using a fully nonlinear Boussinesq model, FUNWAVE 2.0. Based on an IG wave separation procedure, this article presents a systematical investigation on how the maximum IG period component amplitude, the bound and free IG waves, and their relative components inside the harbor change with respect to the plane reef-face slope and the incident short wave amplitude under the condition of the 2nd to the 5th modes. For the given harbor and the ranges of the reef-face slope and the incident short wave amplitude studied in this paper, it is shown that both the maximum IG period component amplitude and the free IG wave component amplitude inside the harbor fluctuate widely with the reef-face slope, and their changing trends with the reef-face slope are almost identical with each other, while the bound IG waves inside the harbor seem insensitive to it. Both the maximum IG period component amplitude and those of the bound and free IG standing waves inside the harbor change cubically with the incident short wave amplitude. 相似文献
2.
I. C. Simpson 《地震工程与结构动力学》1978,6(3):247-263
A two-dimensional soil-structure interaction analysis is carried out for transient Rayleigh surface waves that are incident on a structure. The structure is modelled by a three-degree of freedom rigid basemat to which is attached a flexible superstructure, modelled by a single mass-spring system. The structural responses to a given Rayleigh wave train are compared with those that would have been obtained if the free-field acceleration-time history had been applied as a normally incident body wave. The results clearly exhibit the [frequency filtering] effects of the rigid basemat on the incident Rayleigh waves. It is shown that, if seismic excitation of a structure is, in fact, due to Rayleigh surface waves, then an analysis assuming normally incident body waves can considerably over-estimate structural response, both at basemat level for horizontal and vertical motions and for vertical oscillations of the superstructure. However, in the examples considered here, relatively large rocking effects were induced by the Rayleigh waves, thus giving maximum horizontal accelerations in the superstructure that were of comparable magnitude for Rayleigh and normally incident body waves. 相似文献
3.
Junliang Gao Xiaojun Zhou Li Zhou Jun Zang Qiang Chen Haoyu Ding 《Ocean Dynamics》2018,68(12):1663-1681
Oscillations within an enclosed rectangular harbor and a set of partially opened rectangular harbors with various widths and locations of entrance induced by cubic water surface disturbances with different initial heights and locations are simulated using FUNWAVE 2.0 model. The height and the location of the cubic water surface disturbance refer to its thickness and its relative horizontal position inside the harbor, respectively. The water depth inside and outside all harbors is set to be constant. The aim of this paper is to investigate how different heights and locations of the water surface disturbance and various widths and locations of harbor entrance affect the oscillations inside the harbor. Results show that for the given harbors and the range of the initial height of water surface disturbance studied in this paper, all the response amplitudes of various eigenfrequencies increase linearly with the initial height of water surface disturbance. The variations of the initial location of water surface disturbance along the backwall and sidewall of the harbor can significantly change the transverse and longitudinal oscillation patterns of various modes, respectively. The effects of the variations of the width and location of the harbor entrance on the response amplitudes of various resonant modes both depend on the relative positions of their node lines and antinode lines to the harbor entrance. 相似文献
4.
采用间接边界元法（IBEM）,对Rayleigh波入射下两邻近山体的地震响应进行了定量分析。结果表明:与单个山体在Rayleigh波入射下的地震响应相比,两山地形的地震反应规律更为复杂,反应特征受控于入射波频率和山体间距等因素。总体上看:入射Rayleigh波频率较低时,两山间距对双山地形地震反应影响较大。低频波入射,受邻近山体影响,迎波面山体水平位移峰值约为入射波水平位移的6.3倍,放大效应可达单山作用的1.5倍。且山体山脚处竖向位移的频谱振荡更为剧烈,特定频率下山脚的竖向位移反应可达单山放大效应的1.6倍。较高频波入射时,迎波面一侧山体受邻近山体影响较小,且对波表现出明显的屏障效应,背波面山体地震反应强度被削弱。 相似文献
5.
Ira Didenkulova Efim Pelinovsky Tarmo Soomere 《Pure and Applied Geophysics》2008,165(11-12):2249-2264
The problem of tsunami wave runup on a beach is discussed in the framework of the rigorous solutions of the nonlinear shallow-water theory. We present an analysis of the runup characteristics for various shapes of the incoming symmetrical solitary tsunami waves. It will be demonstrated that the extreme (maximal) wave characteristics on a beach (runup and draw-down heights, runup and draw-down velocities and breaking parameter) are weakly dependent on the shape of incident wave if the definition of the “significant” wavelength determined on the 2/3 level of the maximum height is used. The universal analytical expressions for the extreme wave characteristics are derived for the runup of the solitary pulses. They can be directly applicable for tsunami warning because in many cases the shape of the incident tsunami wave is unknown. 相似文献
6.
7.
针对地震动空间差异问题,以半无限空间内平面SV波入射为例,采用波动理论和叠加原理相结合的方法研究地震动的空间特征。首先,分析入射波和反射波在空间内形成质点运动的叠加模式差异,并依此对空间域进行划分;其次,针对不同泊松比和SV波入射角情形研究叠加区与分离区的分界线控制情况;最后,对比分析不同空间域内的质点运动在峰值、持时等方面的特征。研究结果显示:当SV波入射时,叠加区与分离区的分界线通常由z3 （反射P波与反射SV波的分离线）控制;同时存在两种特殊情况,当SV波垂直入射时,分界线由z1 （入射SV波与反射SV波的分离线）控制,当反射SV波幅值为零时,分界线由z2 （入射SV波与反射P波的分离线）控制。在入射波和反射波的影响下,质点运动时程的形状具有水平不变性。三波贡献时段只出现在深度小于z1的质点的运动时程中,且持时随着深度的增加线性减少;双波贡献时段出现在位于叠加区内的质点的运动时程中,持时沿深度先增加后减少;单波贡献时段随着深度的增加而逐渐加长,在分离区达到最大值。质点运动总持时随深度逐渐增加,在分离线z2和z3深度处存在两个拐点。在质点运动峰值方面,靠近自由面的叠加区质点运动峰值变化较大,深度较大的叠加区和分离区的质点运动峰值一般不变。 相似文献
8.
The Pohang New Harbor (PNH), located at the Yongil bay in the northeastern part of Pohang city, South Korea, has experienced extreme wave hazards of about 3.0–5.0 m in elevation due to the seasonal swell from the far ocean. In this paper, both analytical and numerical studies are performed to investigate the wave-induced oscillations in an arbitrary shaped harbor with corner point consideration. By taking the consideration of the actual topography and bathymetry data, the boundary of PNH is constructed. Our theoretical model is based on the assumptions of inviscid, irrotational fluid, infinitesimal wave amplitude, and finally, the Helmholtz equation and its Weber’s solution. The numerical simulations are conducted to analyze the spectral density of the standing waves in PNH at eight respective synthetic record points. The simulation results are validated with real-time measurement data, which is obtained by wave heights and tide gauges at the specified record points within and outside the PNH. To improve the harbor’s design, a tactic such as building the breakwater at the entrance of the harbor is implemented and then spectral density is estimated in the modified geometry of the PNH. The consequential effects are proposed at the same time, suggesting the feasibility of the improvement measures. 相似文献
9.
Xiuying Xing Zhiqing Kou Ziyi Huang Jiin-Jen Lee 《Pure and Applied Geophysics》2013,170(6-8):1149-1168
Tsunamis waves caused by submarine earthquake or landslide might contain large wave energy, which could cause significant human loss and property damage locally as well as in distant region. The response of three harbors located at the Pacific coast (i.e. Crescent City Harbor, Los Angeles/Long Beach Port, and San Diego Harbor) to six well-known tsunamis events generated (both near-field and far-field) between 2005 and 2011 are examined and simulated using a hybrid finite element numerical model in frequency domain. The model incorporated the effects of wave refraction, wave diffraction, partial wave reflection from boundaries, entrance and bottom energy dissipation. It can be applied to harbor regions with arbitrary shapes and variable water depth. The computed resonant periods or modes of oscillation for three harbors are in good agreement with the energy spectral analysis of the time series of water surface elevations recorded at tide gauge stations inside three harbors during the six tsunamis events. The computed wave induced currents based on the present model are also in qualitative agreement with some of the reported eye-witness accounts absence of reliable current data. The simulated results show that each harbor responded differently and significantly amplified certain wave period(s) of incident wave trains according to the shape, topography, characteristic dimensions and water depth of the harbor basins. 相似文献
10.
The influence of the homogeneous and inhomogeneous ionosphere on the orientation angle of the horizontal magnetic vectors of the long-time geomagnetic pulsations is under consideration in this study. It was realized that this angle is small in the case of the homogeneous ionosphere for both the Alfvén and magnetosonic types of oscillations. An increase in the ionospheric electric field was discovered as the ionospheric conductivity changes during the switch from day to night conditions. It is valid only for the initial Alfvén wave. The ionospheric equivalent current systems excited by the initial magnetospheric waves of Alfvén and magnetosonic types as well as their behavior near the terminator were studied for different seasons. For the Alfvén source, seasonal variations of the orientation angle close to sunrise at the equator depend on the type of source: odd or even modes of Alfvén oscillations excite observable pulsations. It was found that the ionospheric two-vortex equivalent current system of the long-period pulsations arising in high-latitudes in the equatorial region alters not only its direction, but its intensity too. The largest anomaly (\sim25% of the source value) would be expected near the terminator. A new experimental method was suggested to recognize the type of incident magnetospheric waves by implementing observations either at a single observatory or at a couple of observatories. In the case of a single observatory it is proposed to study the frequency dependence of the orientation angle of their magnetic components close to sunrise. If the initial wave is magnetosonic, this angle must not be changed as a function of the local time within the wide frequency range of pulsations. When pulsations have an orientation angle sensitive to the presence of the terminator, they may be classified as both Alfvén and magnetosonic. For the Alfvén waves no frequency dependence of the orientational angle is peculiar. On the contrary, magnetosonic waves should be determined as oscillations with an orientational angle proportional to the frequency. These oscillations may be revealed at observatories located on the high-resistance cross sections. The example of the spectral-temporal analysis of pulsation at the equatorial observatory in Huancayo was demonstrated to confirm the proposed experimental technique. A weak dependence of the orientation angle anomaly on the frequency near the terminator was found. The latter is evidence for the dominant contribution of the Alfvén waves to low-latitude and equatorial oscillations. 相似文献
11.
针对三维沉积盆地对球面波的散射问题,发展一种快速宽频间接边界元方法(IBEM)。利用ANSYS建立求解模型,基于Intel-Fortran编译器编译相应的计算程序,对基岩半空间三维半椭球形盆地对球面波的散射进行了数值分析,着重探讨入射波频率、波源埋深、波源与不规则地形(沉积盆地)距离等参数对地震动特性的影响规律,计算方法适用于求解任意复杂形状的局部场地,实现对沉积盆地三维地震响应的频域精细求解。研究结果表明:随着入射波频率增大,沉积盆地相对半空间的放大效应越显著,且干涉效应越强烈;高频波入射时,由于盆地底部透射的体波和盆地内部由体波转换为的面波以及从盆地边缘处透射的体波相互叠加,次方向位移出现一定的边缘效应。位移频谱分析表明,沉积盆地在较低频率时,地表不同点位的主方向位移幅值基本相同;在较高频率域内,地表不同点位的位移频谱特性差别很大;球面波入射与平面波入射相比之下,位移幅值均有所降低。整体来看,随着膨胀波源与盆地水平距离增大,地表主方向最大位移幅值降低,地表次方向位移聚焦区域增加且分布更分散。 相似文献
12.
Harmonic wave response of two 3-D rigid surface foundations 总被引：1，自引：0，他引：1
A boundary element methodology is developed for studying the response of a system of two rigid, massless or massive, surface foundations of arbitrary plan-forms to various harmonic waves under three-dimensional conditions. The method employs the frequency domain Green's function for the surface of the elastic half-space, thereby restricting the discretization only to the soil-foundation interfaces, and isoparametric quadratic quadrilateral boundary elements for increased accuracy. Extensive comparison studies with other known numerical solutions confirm the high accuracy of the proposed method. Detailed parametric studies are conducted in order to study the harmonic wave response of two square foundations as a function of the kind of incident wave, the angles of wave incidence, the wave frequency, the separation distance between the foundations and the amount of mass in each foundation and compare it against that of a single foundation for assessing the through the soil coupling effect. 相似文献
13.
Closed basin seiches have been studied in Port Kembla, Australia, a compound harbour comprising two basins linked by a narrow channel. Despite the irregular geometry, there are well defined closed basin resonances which may be excited by long waves incident on the harbour entrance. The March 2011 Japanese tsunami excited open-basin modes, but did not significantly excite closed-basin modes. This is attributed to the very low incident wave energy at those frequencies. While the direct forcing of a closed basin mode has been extensively studied, the indirect forcing via an independent open-basin mode found here has not been extensively studied. It was found that single basin modes are more readily excited than the higher dual basin harmonics and the role of the irregular geometry in inhibiting some modes is discussed. The non-linear generation of a higher frequency mode unrelated to the forcing mode is demonstrated. 相似文献
14.
基于Biot饱和多孔介质动力学理论,运用Laplace变换和波函数展开法,根据饱和土体与衬砌结构交界面的连续条件和衬砌结构内边界上的应力自由条件,得到饱和土中深埋圆柱形衬砌洞室对瞬态平面P波和SV波散射问题的解答,该解答可以退化成为饱和土中深埋圆柱形空穴或弹性夹塞物的情形,并很容易转换成为对稳态波散射的解.通过与已有的相关问题的解析解答进行对比,验证了该解答的正确性.同时利用Laplace逆变换的数值方法,给出了饱和土和衬砌中应力和位移场在时域内的数值解,通过算例,分析了衬砌厚度、刚度对衬砌内边界处应力集中因子的影响. 相似文献
15.
Resonant transformation of fast magnetosonic (FMS) wave flux into Alfven and slow magnetosonic (SMS) oscillations is investigated in the one-dimensionally inhomogeneous magnetosphere. Spatial distribution of energy absorption rate of FMS oscillations penetrating into the magnetosphere from the solar wind is studied. The FMS wave energy absorption rate caused by magnetosonic resonance excitation is shown to be several orders of magnitude greater than that caused by Alfven resonance excitation at the same surface. It is connected with the spectrum of incident FMS waves. The Kolmogorov spectrum is used in numerical calculations. Magnitude of the Fourier harmonics exciting resonant Alfven oscillations is much smaller than that of the harmonics driving lower-frequency magnetosonic resonance. It is shown that resonant transformation of FMS waves into SMS oscillations can be an effective mechanism of energy transfer from the solar wind to the magnetosphere. 相似文献
16.
Jerome Peng-Yea Maa Cheng-Han Tsai Wen-Jye Juang Hsiang-Maw Tseng 《Ocean Dynamics》2011,61(4):411-423
New analysis of wave records at Hualien Harbor during Typhoon Tim in 1994 reveals that for certain wave periods, the ratios
of measured wave heights among three available wave stations inside the harbor are unique and roughly remain the same during
the severest period of resonance. Since there is no incident infragravity wave (period from 80 to 220 s) information at offshore
boundaries, these unique ratios become the surrogate of background truth for checking the performance of numerical simulations.
A new simulation effort using a large (45 × 17 km) modeling domain, high-resolution (20 × 20 m) grid and the RIDE wave transformation
model were conducted to simulate the observed responses. Comparison of the modeling results with the observations showed reasonable
agreement. Additional model studies using ideal bathymetries with the same grid domain and resolution were also conducted
to help interpret the prototype modeling results. The effects of two types of commonly used remedies were first examined by
using the ideal bathymetry, and then, the prototype bathymetry. The results demonstrated that a single 1-km long, shore-parallel
breakwater could significantly reduce the resonance. The results of using three shore-parallel breakwaters, however, are no
better. More studies to identify the optimum design associated with the shore-parallel breakwater (location, length, etc.)
are necessary for the optimum reduction of resonance at Hualien Harbor. 相似文献
17.
埋地双排复合式管体结构在SH波作用下的动力分析 总被引：1，自引：0，他引：1
以波动理论为基础,采用复变函数法,给出了地下双排复合式管体结构在SH波作用下的解析解。分析了入射波角度、频率变化,管体埋深、内管的厚度变化等参数对管体动应力集中的影响。结果表明:复合式管体内侧的动应力集中峰值明显高于外侧;高频入射时,双排管体在给定距离之间的相互影响较大,动应力集中峰值向邻侧偏移;复合式管体内管越薄,动应力集中峰值越大;垂直入射时,动应力集中峰值受埋深的影响呈周期性变化。 相似文献
18.
The traditional method of exciting channel waves in coal deposits underground consists of firing explosive sources in a mid-seam position generating seam waves of the Rayleigh and Love type. We investigate various source positions and excitation mechanisms within the bedrock structure surrounding the seam to evaluate the effects of source positions adjacent to the seam. The investigation is based on analogue and numerical modelling of half- and full-space cases, for which the excitation and the nature of Rayleigh channel waves are examined. In the analogue modelling, sources, located from mid-seam out into the bedrock, along the edge of a 2D plate model, excited channel waves through a conversion of the free surface Rayleigh wave at the edge of the plate. The excited channel wave belongs to the normal mode range. Frequency-wavenumber analysis shows that the symmetric 2nd mode of the channel wave is excited with frequencies comparable to the forcing frequency of the source signal. The polarization changes from retrograde to prograde, as the wave develops from the front to the rear of the seam, respectively. The amplitude-depth distribution resembles that of an ordinarily excited seam wave, for the symmetric component. However, the antisymmetric component does not show the characteristic change of sign in amplitudes across the mid-seam axis. Numerical modelling with sources located in the bedrock (full-space case) shows that relocating the source away from the seam lowers the frequency content of the excited channel wave. Based on these investigations, the influence of a lower-frequency source signal on the excitation of the channel wave is examined in an analogue experiment. Sources are sited in the bedrock adjacent to the seam at three locations. A lower-frequency wavelet is calculated for each source location from the results obtained in the numerical analysis. For comparison, a higher-frequency wavelet is also used which is known to be optimal for this model geometry when excited by a mid-seam source location. It is found that in two cases the use of the lower-frequency wavelet improves the channel wave excitation, while no amplification is achieved in one case. 相似文献
19.
Sandy beaches typically have one or more shore-parallel bars with superimposed smaller-scale three-dimensional (3D) bars. Knowledge of their morphodynamic behaviour under more realistic wave conditions is limited. This study investigates the response of beaches with two shore-parallel bars to sinusoidally time-varying angles of incidence, using a non-linear morphodynamic model. Different periods and amplitudes of this sinusoidal variation are considered, as well as different time-mean wave angles. For time-invariant and normally incident waves, results show that alongshore rhythmic 3D bars form in the domains of inner and outer shore-parallel bars. The 3D bars in the inner domain are coupled at half the outer-bars wavelength. This phase coupling breaks up when the wave angle varies in time. Initially, regular 3D bars form in the inner domain (free behaviour), which become irregular when 3D bars develop in the outer domain (forced behaviour). The heights of the 3D bars oscillate with time, reaching maximum values when the forcing period is comparable to the system adjustment time scale (∼ 10–20 days). For a time-varying wave angle around an oblique mean, alongshore migrating 3D bars emerge in both inner and outer domains. In contrast, for an oblique (constant) wave angle, 3D bars only form in the inner domain and they hardly migrate alongshore. For any forcing period, the dominant response period of the oscillating bar heights is at half the forcing period when waves are (on average) normally incident, and it equals the forcing period when waves are on average obliquely incident. Compared with time-invariant angles, heights of inner and outer 3D bars are (on average) smaller and larger, respectively, when the angle varies with time, particularly for forcing periods in the order of the system adjustment time scale. Increasing the amplitude of the time-varying wave angle weakens bar growth. Explanations of these results are also provided. 相似文献
20.
This paper presents the analysis of measurements of long waves at the harbor of Marina di Carrara, Italy. Nine pressure gauges
(eight in the inner harbor and one outside the harbor) were used to record continuously the water surface elevation, for about
3 years; incoming short waves were measured using a directional buoy at about 500 m offshore the breakwaters. The analysis
is carried out splitting the energy of the long waves into two bands, i.e., very long waves (VLW; f < 0.003 Hz) and long waves (LW; 0.003 < f < 0.030 Hz); it is found that LW energy is strongly correlated with the energy of the incoming short waves while no correlation
(or very poor) is found for VLW. During energetic sea states, surface elevation spectra of VLW and LW, normalized against
the wave energy of each frequency band, appear to be autosimilar; this suggests that the spectra of the incoming long waves
have a mostly constant shape. Simple numerical computations of harbor resonance, carried out using a mild-slope equation linearized
model, indicate that the amplification of the height of the incoming LW generated by short waves (calculated using empirical
formulae from previous researches by Melito et al. 2007) inside the harbor can be reasonably predicted using such simple approach, assuming that the LW spectra are rectangular.
The shape of the amplification diagram calculated by the numerical model shows reasonable (but not perfect) agreement with
the shape of the normalized measured spectra inside the harbor. 相似文献