首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 906 毫秒
1.
Over the last few decades, a lot of attention has been concentrated on the consequences of marine impacts, especially those caused by the tsunami wave train. Internal solitary waves are similar to the surface waves that commonly occur in the waters of the ocean or large lakes and can have significant effects on oceanic mixing, climate change, the movement of submerged plankton, and the weathering of geological structures. This motion can be severe enough to create natural hazards such as submarine tsunamis in the ocean. These could also even occur in large lakes. The present work aims to contribute to this knowledge base by studying internal wave propagation on a shallow continental shelf following a particular marine impact. A series of laboratory experiments were conducted in order to clarify the movement of an interfacial solitary wave across a uniform slope and a horizontal plateau forming a slope-shelf topography. The results obtained from test runs indicate that the wave maintains its strength, having a direct impact on the natural ecology of the local oceanic environment. Comparison with different seabed topographies is also presented to demonstrate the propagation of an internal wave over a trapezoidal barrier. A better fitting and more appropriate model is employed to examine the relationship between the physical parameters for better predicting the evolution of an internal solitary wave as it moves over a trapezoidal obstacle on a horizontal plateau.  相似文献   

2.
基于Boussinesq方程耦合泥沙运动和地形演变模型,建立海啸作用下泥沙运动数学模型。地形演变模型采用WENO差分格式,并将WENO差分格式与Lax-Wendroff格式和FTBS格式进行对比分析。运用Synolakis、Kobayashi和Young的实验数据分别对水动力模块和地形演变模块进行验证,数值模拟结果与实验数据吻合良好,模型能够很好地模拟海啸波的传播、破碎、上爬、回落过程以及岸滩的冲淤变化过程,该数学模型能够运用到海啸作用下的岸滩演变研究和预测中。  相似文献   

3.
Coastal ecosystems such as mangroves fringing tropical coastlines have been recognized as natural protectors of the coastal areas against destructive attack of a tsunami. In this paper, the authors aim to investigate the interaction of a tsunami wave on a typical mangrove forest and to determine its performance in reducing the run-up. A laboratory experiment using a hydraulic flume with a mangrove forest model was carried out in which tests were conducted by varying the vegetation widths of 0, 1, 2 and 3?m and average densities of 8, 6 and 4 trees per 100?cm2 using a scale ratio of 1:100. Two conditions of water levels were considered in the experiments at several tsunami wave heights between 2.4 and 14?cm. The dam break method used in the experiments produced two types of waves. At low water condition, a bore was developed and subsequently, a solitary wave was produced during high water. The results of the experiments showed that in general, vegetation widths and densities demonstrate a dampening effect on tsunami run-up. A larger vegetation width was found to be more effective in dissipating the wave energy. The first 1?m width of mangrove forest could reduce 23?C32?% during high water and 31?C36?% during low water. Increasing the mangrove forest width to 2 and 3?m could further increase the average percentage of run-up reduction by 39?C50?% during high water and 34?C41?% during low water condition. It was also observed that densities of the mangrove forest do not influence the run-up reduction as significantly as the forest widths. For mangrove forest densities to be significantly enough to reduce more tsunami run-up, an additional density of 4 trees/100?m2 needs to be provided. The experiments also showed that mangrove roots are more effective in reducing the run-up compared to the trunks and canopies. The experiments managed to compare and present the usefulness of mangrove forests in dissipating wave energy and results produced are beneficial for initiating design guidelines in determining setback limits or buffer zones for development projects in mangrove areas.  相似文献   

4.
In the present study, laboratory experiments were conducted to validate the applicability of a numerical model based on one-dimensional nonlinear long-wave equations. The model includes drag and inertia resistance of trees to tsunami flow and porosity between trees and a simplified forest in a wave channel. It was confirmed that the water surface elevation and flow velocity by the numerical simulations agree well with the experimental results for various forest conditions of width and tree density. Further, the numerical model was applied to prototype conditions of a coastal forest of Pandanus odoratissimus to investigate the effects of forest conditions (width and tree density) and incident tsunami conditions (period and height) on run-up height and potential tsunami force. The modeling results were represented in curve-fit equations with the aim of providing simplified formulae for designing coastal forest against tsunamis. The run-up height and potential tsunami forces calculated by the curve-fit formulae and the numerical model agreed within ± 10% error.  相似文献   

5.
Over the last few decades, a lot of attention has been concentrated on the consequences of marine impacts, especially those caused by the tsunami wave train. Internal solitary waves are similar to the surface waves that commonly occur in the waters of the ocean or large lakes and can have significant effects on oceanic mixing, climate change, the movement of submerged plankton, and the weathering of geological structures. This motion can be severe enough to create natural hazards, such as submarine tsunamis in the ocean. These could also even occur in large lakes. Numerical modeling has shown that the waveform of a soliton that interacts with others of a similar kind would emerge unchanged from the collision, except for a phase shift. However, the results from laboratory experiments are rather limited, despite the successful generation of ISWs using a collapse mechanism in a wave flume. This paper reports on some interesting facts compiled from the results of a series of laboratory experiments on the investigation of the head-on collision of two ISWs. Our results confirm that the waveforms of two depression ISWs will more or less retain their initial shape after a head-on collision. However, the transmitted wavelength will broaden when two elevation ISWs collide, perhaps affected by bottom friction. Overall, the resulting waveforms induced by such head-on collisions agree well with the theoretical predictions for depression ISWs, regardless of their scale of amplitude, but the results are only valid for elevated waveforms of large amplitude.  相似文献   

6.
Pedersen  G. 《Natural Hazards》2016,84(2):599-619
A general framework for derivation of long wave equations in narrow channels, and their transformation to Lagrangian coordinates is briefly established. Then, fully nonlinear Boussinesq equations are derived for channels of parabolic cross sections. The simplified version with normal nonlinearity is compared with corresponding models from the literature, and propagation properties are discussed. A Lagrangian run-up model is adapted to the fully nonlinear set. This model is tested by means of controlled residues and by a well-controlled comparison to exact analytic solutions from the literature. Then, run-up of solitary waves in simple geometries is simulated and compared to a semi-analytic solution that is derived for propagation and run-up in a composite channel. The dispersive model retains the higher run-up height in a parabolic channels, as reported in the recent literature for NLSW solutions, as compared to a rectangular channel.  相似文献   

7.
为揭示内部渗流对海岸冲流带泥沙起动的影响,系统地开展了斜坡海床冲流特性与泥沙起动机理研究。通过室内水槽开展了孤立波在可渗透和不可渗透斜坡海床上的冲流试验,测试了冲流过程中波高、波速等变化规律;建立了渗透海床冲流数值模型并通过试验结果进行验证;深入分析了床面渗流对其波浪流场动态特征以及床面泥沙起动的影响机理。研究表明,床面渗流作用加剧波浪的不对称性,在波浪上冲过程中因床面强入渗作用而增大了床面切应力;回流过程因入渗所造成流量损失而导致床面切应力减小。床面渗流引起床面颗粒有效重度和切应力变化而导致泥沙希尔兹数大大增加,加剧了泥沙起动现象,且床面切应力改变是引起泥沙希尔兹数变化的主要因素。  相似文献   

8.
In this work, a two-dimensional fourth-order Boussinesq-type numerical model is applied to estimate the impact of landslide-generated waves in dam reservoirs. This numerical model has recently been extended for simulating subaerial landslides. The extended model is validated using available three-dimensional experimental data, and a good agreement is obtained. The numerical model is then employed to investigate the impact of landslide-generated waves in two real cases, the Maku and Shafa-Roud dam reservoirs in the northwestern and the north of Iran, respectively. Generated wave heights, wave run-up, maximum wave height above dam crest, and dam overtopping volume have been estimated for each case. The amplitude of generated waves about 18 and 31 m and the volume of dam overtopping up to 80,000 m3 emphasize the importance of the estimation of the landslide-generated waves in dam sites.  相似文献   

9.
This paper presents a study of the effects of a potential landslide in La Yesca Reservoir, Jalisco-Nayarit, Mexico. The main purpose of the paper is to predict the maximum wave amplitude, wave run-up, and dam overtopping. The landslide is formed by an unstable slope of more than 24 Mm3 that is partially submerged for the range of the reservoir operation levels. The dynamics of the sliding mass were obtained in detail considering that it moves over a pair of failure surfaces with the potential rupture of a third surface. The paper presents results of a physical model of the reservoir based on Froude similitude (scale 1:200). Impulse waves are produced with a solid wedge shape slide as it moves on rails. The movement was calibrated to reproduce the dynamics of the landslide. Also, numerical modelling of the event was performed with a 2D implicit model that solves the two-dimensional shallow water equations. In this case, the impulse waves were generated at each time increment with the variation of the ground elevation (obtained from the dynamics of the landslide) for the mesh points where the landslide passes. The results of both studies are similar.  相似文献   

10.
After the Gongjiafang tsunami incident, the China Geological Survey recognized the extreme importance of subaerial landslide-generated tsunamis (SLGT) in the Three Gorges Reservoir, western China. The experimental models presented in the present paper were rooted in two common failure types of high, steep slopes in the Three Gorges Reservoir. One model represents a rigid rock plunging into the water and the other is a granular cluster sliding into the water. A wide range of effective parameters were considered and studied by performing 74 laboratory tests. The effects of bed slope angle, water depth, slide impact velocity, geometry (three-dimensional size of the rigid block and grain size of the granular cluster), and volume on impulse wave characteristics were examined. Slide kinematics and impulsive wave features, such as wave shape, amplitude, run-up, and run-down, were studied and compared. Experiments showed that the failure type of the rock mass plays a key role in SLGT and strongly influences air–fluid–solid interaction. Thus, to forecast SLGT rapidly, the zone of complicated air–solid–fluid interaction can be treated as a “black box” whose output is a water wave with definable characteristics, such as amplitude. Based on the experimental results, two dimensionless equations for the estimation of primary wave maximum amplitude were developed and successfully verified for the two failure types. The study provides basic information needed to forecast tsunamis generated by slopes with the potential to fail in other reservoirs around the world. These data can also be a very useful resource for theoretical analysis or numerical model validation.  相似文献   

11.
At 4:40p.m. on November 23, 2008, the Gongjiafang slope collapsed on the north bank of Yangtze River in Wu Gorge of Three Gorges Reservoir. The 380,000-m3 sliding mass consisted mainly of cataclastic rock. A video record of the major sliding incident was analyzed using the general laws of physical motion. The analysis indicated that the maximum speed and maximum acceleration of the sliding mass were 11.65?m/s and 2.23?m/s2, respectively, and that the maximum amplitude and the propagation velocity of the water wave near the landslide were 31.8?m and 18.36?m/s, respectively. Wave run-up investigation indicated that the maximum run-up on shore was 13.1?m, which declined to 1.1?m at Wushan dock 4?km away. The incident causes no casualties, but did result in economic losses of RMB five million. The numerical simulation model GEOWAVE was used to simulate and reproduced the impulse wave generated by the landslide; the results were in good agreement with the observed incident. The numerical simulation data were then applied to analyze the decay and amplification effects of the landslide wave in the river course. The field investigations and witness information provide valuable materials for the studies of landslide kinematics and impulse waves generated by landslides. In addition, the research results provide a useful reference for future similar waves generated by landslides in reservoirs.  相似文献   

12.
A theoretical model explaining the effect of anomalous suppression of the energy (up to 70%) of tsunami-type waves by thin (compared to the wavelength) underwater obstacles is developed based on the integral laws of conservation of mass and energy fluxes. It is shown that the analytical dependences for the coefficients of reflection and transmission of waves across an underwater obstacle that have been obtained using the theoretical model proposed by the author agree with the results of the experiments and numerical simulation based on the complete Navier–Stokes equations.  相似文献   

13.
Subaerial landslides falling into confined water bodies often generate impulsive waves. Damaging landslide tsunamis in Three Gorges Reservoir, China, have struck several times in the last 15 years. On June 24, 2015, a 23?×?104 m3 slope failure occurred on the east bank of the Daning River opposite Wushan Town. The sliding mass intruded into the Three Gorges Reservoir and initiated a reservoir tsunami that resulted in two deaths and significant damage to shipping facilities. A post-event survey revealed the landslide geometry and wave run-up distribution, while an eyewitness video captured most of the landslide motion. Employing these firm constraints, we applied the Tsunami Squares method to simulate the 2015 Hongyanzi landslide and tsunami. The simulation revealed that the landslide experienced a progressive failure in the first few seconds and impacted the water with a maximum velocity of ~?16 m/s. The initial wave propagated to the opposite shore in an arch shape, and the water surface reached a maximum amplitude of ~?11 m near the landslide. Wave amplitude-time curves at four points on the river cross section show that the initial wave reached Wushan town in about 50 s with an average wave velocity of ~?30 m/s. The maximum wave run-ups on the shoreline opposite the landslide are around 6 m and attenuate to less than 1 m beyond 2-km distance. The landslide simulation matches the observed geological profile and the eyewitness video, and the numerical results coincide with the observed wave run-up heights. Nearly 80% of landslide energy is lost due to frictional resistances, but the remaining fraction imparted to the tsunami carried catastrophic consequences to a large region. The numerical results emphasize the efficiency and accuracy of Tsunami Squares method for a “Quick Look” simulation of a potential landslide.  相似文献   

14.
为研究大波幅波浪作用下,非完全淹没水平圆柱所受波浪力的特征,基于黏性流理论采用有限体积法建立两相流数值波浪水槽模型,对不同波幅和圆柱垂向位置下非完全淹没水平圆柱所受波浪力进行了数值计算,并对波浪力和冲击力的特征进行了分析,讨论了冲击力与冲击速度的关系,结合经验计算公式拟合得到了冲击力系数。结果表明:波浪力的大小受波幅和圆柱垂向位置的影响比较显著,其影响机理与波浪场流体运动特性相关;冲击力的大小与冲击速度密切相关,而垂向冲击力在波浪力中起主导作用时,对应的最小预测冲击速度受圆柱垂向位置影响并不显著;不同圆柱垂向位置下冲击力系数随着波幅增大由分散性较强逐渐趋于集中。  相似文献   

15.
We investigate the hitherto unexplained wave which inundated the village of Dwarskersbos, South Africa, in the early hours of August 27, 1969, in the absence of any seismic disturbance or major meteorological storm. A field survey, based on the interview of nine elderly witnesses still residing in the community, documented maximum run-up of 2.9 m, concentrated on an extremely short segment of coastline, less than 2 km in length. These characteristics are incompatible with generation by a seismic source (which, at any rate, should have been felt by the population). A landslide source, located at the only canyon featuring a steep enough ocean floor, is also ruled out since a numerical simulation fails to reproduce the concentration of the wave at Dwarskersbos. By contrast, the wave can be explained as a “meteo-tsunami” resulting from resonance between a meteorological squall propagating at 18 m/s in the azimuth \(\hbox {N101}^{\circ }\hbox {E}\) and a gravity wave propagating in the shallow waters off the eastern shore of St. Helena Bay. This is confirmed by numerical simulation under the formalism of Proudman (Dynamical oceanography. Methuen, London, 1953), which provides a satisfactory model of the distribution of run-up along the beach.  相似文献   

16.
在两层流体中,内波的特性受到许多控制变因的影响,其中包括上下层水深比、造波区位能差(位能大小)、上下层的密度比等。本文以成功大学水工试验所研发的MNDAS套装软件记录,协助数据分析及处理,研究上下层水深比对内波波型的影响,当水深比值差异越大造成的孤立波形与明显,且Kdv及修正mKdV可以合理描述内波振幅与频率之间的关系。  相似文献   

17.
This paper presents a numerical simulation of S-wave propagation across a rough, filled discontinuity using the universal distinct element code (UDEC). The ability of UDEC to simulate a stress wave across a smooth and planar discontinuity filled with an elastic material is validated through comparisons with analytical solutions. Next, the effect of the plastic deformation of the fill on the wave propagation is investigated. The model is extended to further study S-wave propagation across a filled discontinuity with rough interfaces, which is described using a sawtooth. The transmission coefficient defined by the energy is used to measure the wave attenuation. Finally, a parametric study is conducted to investigate the influences of the filled thickness, asperity angle, and incident amplitude on the transmission waves and transmission coefficients. The asperity angle and filled thickness together determine the transmitted waveform and transmission coefficient. The transmitted wave may be cut off when the incident wave amplitude exceeds a threshold value. The transmission coefficient decreases with a different trend with the incident wave amplitude increasing when the asperity angle varies. Compared with planar discontinuity, a filled discontinuity with rough interfaces is more sensitive to the amplitude of the incident wave. The causes of these phenomena are analyzed in detail. In addition, the deformation of the fill material is strongly related to the wave attenuation.  相似文献   

18.
Models of moving interfaces, especially those with stable soliton-like behavior, are of central importance in many areas of physics, for example, surface growth models, chemical waves, and more. Here described for the first time in a realistic geophysical context is a partial differential equation model of bedrock abrasion by unidirectional impacts generalizing earlier pioneering work on pebble shapes by Bloore who treated isotropic impacts (Bloore in Math. Geol. 9:113–122, 1977). The result is a simple geometrical partial differential equation exhibiting circular arcs as solitary wave profiles. The latter seem to be the first known analytic solutions on Bloore-type models. Solitonic behavior, although familiar in many areas of physics, appears not to have been encountered in the geophysical literature. Not only are the existence and stability of these stationary, traveling shapes demonstrated here by numerical experiments based on finite difference approximations, but it is also shown that the results received here are consistent with recent laboratory experiments. The simulations within show that, depending on initial profile shape and other parameters, these circular profiles may evolve via long transients, which in a geological setting, may appear as noncircular stationary profiles.  相似文献   

19.
有别于国内现行广泛应用Navie-Stokes方程进行地质灾害涌浪的数值模拟技术,本文采用波浪理论对地质灾害涌浪波进行了分析。地质灾害涌浪波是非周期性波,并且有强烈的非线性,介于中等水波至浅水波之间;可用浅水波模型和Boussinesq模型进行数学描述。本文采用有限差分法的Boussinesq模型,以三峡库区龚家方崩滑体涌浪为例,模拟了涌浪波的传播和爬高问题。该模型能够计算形成涌浪瞬时河面、河面最大波高图、最大流速矢量图、最大爬坡和预警分布图。模拟计算结果与调查结果吻合非常好。这说明基于波浪理论的地质灾害涌浪分析方法精度较高,为涌浪的预测研究提供了一种新的研究方法。  相似文献   

20.
Landslide-related impulse waves are catastrophic but accidental, so limited data on field measurements are available; scaled physical experiment is therefore a functional method to simulate and analyze this phenomenon. A large-scale physical Froude-similar model to produce impulse waves was constructed based on the Chinese Gongjiafang landslide, which occurred on the main stream of Three Gorges after the impounding in the reservoir in China. With a scale of 1:200, the model had the dimensions of 24, 8, and 1.3 m. Four water levels, 145, 156, 172.8, and 175 m, were modeled for the experiments, and marble coarse sands were used to imitate the actual cataclastic rock mass. Wave height gauges, high-speed cameras, and run-up measuring instruments were used to monitor wave fluctuations in the model. Among the experiments, the ones modeled using a water level of 172.8 m best confirmed the actual conditions in the Gongjiafang landslide, representing a good validation of the experiments. This study obtained, for the first time, specific data on the reproduced impulse waves’ convergence and superposition during propagation, and of the energy change between impulse waves and reflected waves. The test data describe a rapid decaying and gradual decaying rule for the wave heights and run-ups. The Froude-similar experiments presented in this article help us to understand the whole procedure of impulsive wave generated by cataclastic rock mass failure, and the results acquired contribute to studies of impulse waves caused by similar bank destabilizations worldwide.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号