Ion acoustic solitons and double layers in electron–positron–ion plasmas with dust particulates

Propagation of small but finite amplitude ion acoustic solitons and double layers are investigated in electron–positron–ion plasmas in presence of highly negatively charged impurities or dust. The presence of negatively charged dust particulates can result in existence of two critical concentrations of ion–electron density ratio α. One of them α _D decides the existence of double layers, whereas the other one α _R decides the nature of the solitons and double layers. The system supports both compressive and rarefactive solitons as well as double layers. The parameter regimes of transitions from compressive to rarefactive solitons and double layers are also specified.     

南海东北部深水海域大振幅内孤立波SAR遥感仿真研究

为了克服基于两层海洋的内孤立波SAR遥感仿真模型的缺陷,使用基于连续分层海洋模型的GK-dV方程,在南海东北部深水海域进行了大振幅内孤立波传播模拟,模拟输出内孤立波振幅91.0m,半波宽度262.0m。然后使用新建立的基于连续分层海洋模型的内孤立波SAR遥感仿真模型进行了内孤立波反演,反演出内孤立波半波宽度251.5m...     

内孤立波与深海立管相互作用数值模拟

提出了一种对内孤立波与深海立管相互作用耦合数值模拟方法。流场采用内孤立波数值水槽方法进行模拟,结构响应采用基于薄壳理论的有限元方法进行计算,采用一种将流场和结构响应数据进行实时传输的方法,实现了流体与固体之间的耦合数值模拟。对内孤立波作用下某长径比为1 200的深海立管载荷及其动力响应特性进行了数值模拟与分析。结果表明内孤立波不仅会对深海立管产生突发性剪切载荷作用,而且还会使立管产生大幅度变形响应现象,因此在深海立管设计与应用中,内孤立波的影响是不可忽视的。研究表明,该方法为研究内孤立波作用下深海立管动力特性及其工程预报相关问题提供了一种有效的手段。     

INTERNAL TIDES, SOLITARY WAVES AND BORES IN SHALLOW SEAS

Remote sensing and in situ observations of internal tides, solitary waves and bores in shallow water are briefly reviewed in this paper. The emphasis is laid on interpreting SAR images based on oceanographic measurements, and analyzing characteristics of internal waves in the China Seas. Direc-tions for future research are discussed.     

Modification on Lynett and Liu’s model for internal solitary wave propagation over variable bathymetry

1 INTRODUCTION As an important wave phenomenon, taking place inside the ocean, the internal wave has drawn attentions of many scientists. More and more in- formation about it have been provided by both CTD and ADCP data and the images captured by the synt…     

Review of the Seabed Sediment Resuspension by Internal Solitary Wave

Internal Solitary Waves (ISWs) are nonlinear, large amplitude motions of the interface between two fluids with different densities in the stratified ocean. Because of their strong vertical and horizontal current velocity, and the vortex, turbulent mixing caused by breaking, they affect marine environment, seabed sediment and man-made structures in the ocean. In the paper, we systematically analyzed and summarized the ISW-induced shoaling break mechanisms, models of suspension, and seabed dynamical response. Then, we discussed the ISW-induced sediment resuspension criteria, forming bottom and intermediate nepheloid layer and the capacity to suspend sediments in the seabed, and further put forward the unsolved problems based on the conducted work and related achievements. In shallow seas with complex terrain variations, shoaling can cause ISWs to deform, break, and split. Studies on the propagation of ISWs of depression over sloping topography have shown that an adverse pressure gradient causes the rotation of the flow separation, which produces vortices, and this results in global instability of the boundary layer and ISW burst. The separation vortices increase the bottom shear stress, vertical velocity, and near-bottom Reynolds stress, which leads to sediment resuspension and transport in the flow and vortex core. Although episodic, ISW-induced resuspension is hypothesized to be important enough to shape the topography. Shoaling ISWs may erode, resuspend and transport mud-like sediments, first towards shore by boluses, and subsequently offshore through the generation of intermediate nepheloid layers. Shoaling ISWs might be an important mechanism of muddy sediment dispersal along continental shelves. Furthermore, recent hypotheses suggest that sediment mobilization and transport caused by internal waves in general, and ISWs in particular, may be at the origin of some sedimentary structures found in the sedimentary rock record and also the hummocky-cross stratification. Observed on-shelf propagating frontal ISW most likely interacts with the sand waves, sediment waves or sand dunes. ISWs contribute to their generation, as they are trailed by considerable shear-induced turbulence and high-frequency internal waves close to the buoyancy frequency. This work is of great value for further understanding the process of ISW-induced sediment resuspension, transportation, and the capacity to suspend sediments in the seabed. It helps further study of the dynamic process of marine ecological environment dynamic process by ISW and the deep sea sedimentation process.     

Solitary wave propagation influenced by submerged breakwater

The form of Boussinesq equation derived by Nwogu （1993） using velocity at an arbitrary distance and surface elevation as variables is used to simulate wave surface elevation changes. In the numerical experiment, water depth was divided into five layers with six layer interfaces to simulate velocity at each layer interface. Besides, a physical experiment was carried out to validate numerical model and study solitary wave propagation.“Water column collapsing”method （WCCM） was used to generate solitary wave. A series of wave gauges around an impervious breakwater were set-up in the flume to measure the solitary wave shoaling, run-up, and breaking processes. The results show that the measured data and simulated data are in good agreement. Moreover, simulated and measured surface elevations were analyzed by the wavelet transform method. It shows that different wave frequencies stratified in the wavelet amplitude spectrum. Finally, horizontal and vertical velocities of each layer interface were analyzed in the process of solitary wave propagation through submerged breakwater.     

深圳地区花岗岩球状风化体地下分布规律统计分析

深圳花岗岩发育地区球状风化体(俗称孤石)广泛分布,对地下工程建设产生了不利的影响.通过对深圳地区花岗岩孤石大样本的统计分析,得到如下统计结论:深圳地区花岗岩孤石主要成份是微风化花岗岩,60％以上分布在强风化花岗岩层中,残积层和全风化层中也有分布,孤石层面分布高程集中在40.00～70.00m(黄海高程)区间内;80％的孤石揭示“厚度”不超过2.50m,三分之二花岗岩孤石主要发育一层,随着发育层数的增多,出现频率锐减.     

Seasonal and spatial variations of kinematic parameters of internal solitary waves in the Andaman Sea

The horizontally variable density stratification and background currents are taken into the variable-coefficent extended Korteweg-de Vries(evKdV) theory to obtain the geographical and seasonal distribution of kinematic parameters of internal solitary waves in the Andaman Sea(AS). The kinematic parameters include phase speed,dispersion parameter, quadratic and cubic nonlinear parameters. It shows that the phase speed and dispersion parameter are mainly determined by the topographic feature and ha...