Numerical study of enhanced energy dissipation near a seamount     

Nobuyuki Iwamae  Toshiyuki Hibiya  Yoshihiro Niwa 《Journal of Oceanography》2006,62(6):851-858

Using a two-dimensional primitive equation model, we examine nonlinear responses of a semidiurnal tidal flow impinging on a seamount with a background Garrett-Munk-like (GM-like) internal wavefield. It is found that horizontally elongated pancake-like structures of high vertical wavenumber near-inertial current shear are created both in the near-field (the region over the slope of the seamount) and far-field (the region over the flat bottom of the ocean). An important distinction is that the high vertical wavenumber near-inertial current shear is amplified only at mid-latitudes in the far-field (owing to a parametric subharmonic instability (PSI)), whereas it is amplified both at mid-and high-latitudes (above the latitude where PSI can occur) in the near-field. In order to clarify the generating mechanism for the strong shear in the near-field, additional numerical experiments are carried out with the GM-like background internal waves removed. The experiments show that the strong shear is also created, indicating that it is not caused by the interaction between the background GM-like internal waves and the semidiurnal internal tides. One possible explanation is proposed for the amplification of high vertical wavenumber near-inertial current shear in the near-field where tide residual flow resulting from tide-topography interaction plays an important role in transferring energy from high-mode internal tides to near-inertial internal waves.  相似文献   

辽东湾S2冰侧限剪切强度的试验研究   总被引：3，自引：0，他引：3  

李志军孟广琳  高树刚刘培林 《海洋工程》2002,20(1):20-23

利用试验方法系统地研究了辽东湾S2型海冰侧限剪切强度随剪切应变速率、加载方向、法向应力、温度和冰内孔隙率的变化规律。介绍了S2型海冰各向异性特点及剪切应变速率对剪切破坏方式的效应和韧脆破坏转变的条件。分析了不同加载方向海冰峰值剪切强度的差异 ,获得 - 6 2℃温度下S2冰内摩擦角和内聚力分别为 42°和 70 0kPa。利用统计分析给出峰值剪切强度与冰温和孔隙率的试验关系  相似文献   

Gradation affects basic mechanical characteristics of Chinese calcareous sand as airport subgrade of reefs     

Shen Yang  Xue Shen  Hanlong Liu  Huayang Ge  Xiaoxi Rui 《Marine Georesources & Geotechnology》2020,38(6):706-715

Abstract

Construction of the reefs in the South China Sea is a significant foundation to the secure stability and economic development of China. The construction of an airport runway is necessary for this realization. The calcareous sand is the main primary material in the runway construction. A certain type of calcareous sand near a certain reef of the South China Sea was studied in this paper. To investigate this specific calcareous sand, quartz sand was used as a reference for comparison. Microscopic 3-D imaging, compression and triaxial tests were conducted to test the micro, squeezing and shear properties. The effect mechanism of gradation on the calcareous sand’s compressibility and shear characteristics are discussed from a mesoscopic viewpoint using 3-D morphology. Calcareous sand particles are multiangular and flatter in comparison with quartz sand. The larger the particle sizes are, the more different the two sands’ morphologies are. The compressibility of calcareous sand is greater, and the effect of the coarse fraction (5–1?mm) content in the gradation plays the most significant role in this feature. When the coarse particles’ content is less than 25% and the mass ratio of the middle and fine particles (M) is constant, there is the worst coarse fraction content causing the calcareous sand to be most likely compressed. The worst coarse fraction content decreases with the increase in M, and an empirical formula is proposed. When the gradation, relative density and confining pressure are the same, the peak shear stress and strain of calcareous sand are all at a high level. The effect of confining pressure is manifested in calcareous sand. The shear strength and dilation of calcareous sand are also most affected by the medium coarse fraction (5–0.25?mm) content.  相似文献   

Distribution of population-based indicators across multiple taxa to assess the status of Gulf of Alaska and Bering Sea groundfish communities     

Mueter  Franz J.; Megrey  Bernard A. 《ICES Journal of Marine Science》2005,62(3):344-352

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16米风化砂回填地基的深层振密加固     

曹永琅  张光蒲  丛健 《海岸工程》2001,20(4):21-26

结合北方某重力式深水 ( -1 6.0 m)码头沉箱后壁 1 4.5 m范围的回填风化砂经深层振密处理这一工程实例 ,介绍了回填砂振密的技术要求、施工工艺和方法及振密效果的检测。同时对施工与检测中的某些技术问题提出了自己的看法。  相似文献   

A Preliminary Study of Shear Wave in Seafloor Surface Sediments   总被引：1，自引：0，他引：1  

Bo Lu  Ganxian Li  Shaojian Huang 《Marine Georesources & Geotechnology》2006,24(1):17-28

This article preliminarily reports and analyses the transmission characteristics and behaviors of shear wave in the offshore seafloor surface sediments in China, discusses the relationships between the physical and mechanical features of the shear wave and the compression wave, and compares the testing results with that of Hamilton and Chen et al. The result shows that the shear wave can be tested if the seafloor surface sediment has tangent modulus. The shear wave velocity ranges from 50-600 m/s and the measuring frequency from 50-200 kHz. The sound velocity rate of shear wave and compression wave can be used to appraise the stress-strain feature of seafloor surface sediments. This study provides a basis for further describing and appraising the seafloor sedimentary acoustic-mechanical feature and building a geological-acoustic model on China's offshore sea area.  相似文献   

0220号热带风暴(米克拉)特征分析     

李孟植 《海洋预报》2003,20(3):7-11

南海是热带气旋活动较为频繁的地区之一。该地区因其独特的地理环境和复杂的热带大气环流系统，在热带气旋预报工作上存在一定的困难。本文在分析一些气象图表资料的基础上，对2002年第20号热带风暴(米克拉)的形成、发展及消亡进行了探讨和研究。主要从形成的背景环流，气旋的结构等方面入手，总结出一些该气旋所具备韵特有流场，从而为以后的南海自生热带气旋预报工作积累一定经验。  相似文献   

海底浅层介质切变波的初步研究   总被引：2，自引：0，他引：2  

卢博  李赶先  黄韶健 《热带海洋学报》2004,23(4):11-18

初步分析了中国沿海海底浅层介质切变波的传播特性,讨论了多种海底浅层介质切变波与压缩波、物理力学性质之间的关系,并与Hamilton和Chen等人的结果进行了比较。认为海底浅层介质存在切变模量,切变波可以被测量出来,切变波速为50—600m·s-1,测量频率在50—200kHz之间,用波速比可以评价海底浅层介质的应力 应变性质。研究工作有助于描述和评价中国沿海海底浅层介质声学物理性状,并为最终建立中国沿海海底地声模型提供依据。  相似文献   

Experimental investigation on a two-part underwater towed system     

Jiaming Wu  Allen T. Chwang 《Ocean Engineering》2001,28(6)

An experimental set-up is developed and proved to be effective for laboratory study of an underwater towed system. The experimental technique gives a practical method for monitoring the kinematic and dynamic performance of an underwater towed system in a ship towing tank. Both the theoretical and experimental results in the investigation indicate that the hydrodynamic response of a towed vehicle to the wave induced motion of a towing ship can be significantly reduced by applying a two-part tow method. A comparison of the numerical and experimental results in the investigation demonstrates that the numerical simulation results are close to the experimental data, overall agreement between experimental and theoretical results is satisfactory. The results qualitatively verify the mathematical model of a two-part underwater towed system proposed by Wu and Chwang [Wu, J., Chwang, A.T., 2000. A hydrodynamic model of a two-part underwater towed system. Ocean Engineering 27 (5), 455–472].  相似文献   

利玛原甲藻腹泻性毒素的生物学测定   总被引：1，自引：0，他引：1  

邱德全  林永水  周近明  熊仕林 《热带海洋学报》1996,(4)

１９９４年和１９９５年分季度从海南省三亚海区采集附生于褐藻上的利玛原甲藻Ｐｒｏｒｏｃｅｎｔｒｕｍｌｉｍａ（Ｅｈｒｅｎｂｅｒｇ）Ｄｏｄｇｅ，经丙酮提取。提取液用ｐＨ＝３的水除去麻痹性贝毒（ＰＳＰ），取残留液注入小白鼠（ＢａＢ／Ｃ纯系），有腹泻性贝毒（ＤｉａｒｒｈｅｔｉｃＳｈｅｌｌｆｉｓｈＰｏｉｓｏｎｉｎｇ即ＤＳＰ）中毒的症状出现。初步确定此种藻中提取的毒素为ＤＳＰ。  相似文献