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1.
In order to test dynamic response of storm serges to the track, the intensity and the speed of typhoon on the coastal areas of Zhejiang and Jiangsu Provinces, the authors have made an attempt to simulate the model tyhoon surges on that regions. This work has been carried out by the finite-difference scheme with the quadratic conservation. The model tyhoons have been assumed to hit the coast of Zhejiang and Jiangsu provinces along the five main tracks and to be different in the intensity and the travelling speed respectively, By this computation some conclusions which are useful to further simulate typhoon surges on those regions have been obtained. 相似文献
2.
Foundation piles of the offshore oil platforms in the Bohai Bay are usually longer than 100 m with a diameter larger than 2 m.Driving such long and large-sized piles into the ground is a difficult task.It needs a comprehensive consider ation of the pile dimensions,soil properties and the hammer energy.Thoughtful drivability analysis has to be performed in the design stage.It has been shown that judging whether the soil column inside the pile is fully plugged,which makes the pile behave as close-ended,strongly influences the accuracy of drivability analysis.Engineering practice repeatedly indicates that the current methods widely used for soil plug judgment often give incorrect results,leading the designers to make a wrong decision.It has been found that this problem is caused by the ignorance of the bearing capacity provided by the soil surrounding the pile.Based on the Terzaghi’s bearing capacity calculation method for deep foundation,a new approach for judging soil plug status is put forward,in which the surcharge effect has been considered and the dynamic effect coefficient is included.This approach has been applied to some practical engineering projects successfully,which may give more reasonable results than the currently used method does. 相似文献
3.
The growing demand of prawn protein in the world has been demanding an increasing catch of prawn from the sea which, however, fails to meet the needs due to over exploitation. This ease has always been a keen subject among us fishery seientists. With the support and guidance of the Provincial Government of Shandong, the Shandong Fishery Bureau has been carrying out a project of "the Ex- 相似文献
4.
ANALYSIS OF DYNAMIC STABILITY OF SUBMERGED STRUCTURE 总被引：2，自引：0，他引：2
《中国海洋工程》1990,(2)
The submerged structure is basically a large three-dimensional structure of few statically redundant members. The structure is subjected to vertical dead and live loads in addition to the wave forces. An analysis of dynamic stability of the submerged structure without damping has been made by J. Thomas and Abbas (1980). In this paper the analyses of dynamic stability of the sumberged structure with damping are conducted. The case structure with damping is more complicated 'than the case without it. According to the principle of perturbation, a new model for dynamic stability calculation in consideration of damping effect is developed. In this paper, the formulas are deduced, the computational program is compiled, the practical examples are analysed, and this problem is solved very satisfactorily. The computational results show that the shape and value of the regions of dynamic instability can be changed significantly by damping. So only by considering damping can the property of dynamic stability of the submerged structure be reflected correctly. 相似文献
5.
The series connection of multistage pumping module is the common concept of deepwater riserless mud recovery drilling system. In this system, the influence of the mass of pumping module on the vibration of mud recovery line cannot be ignored, and the lumped mass method has been utilized to discretize the mud recovery line. Based on the analysis of different boundary conditions, the paper establishes the axial forced vibration model of the mud recovery line considering the seawater damping, and the vibration model analysis provides the universal solution to the vibration model. An example of the two-stage pumping system has been used to analyze the dynamic response of mud recovery line under different excited frequencies. This paper has the important directive significance for the application of riserless mud recovery drilling technology in deepwater surface drilling. 相似文献
6.
The present research aims at clarifying the effects of freak wave on the motion and dynamic responses of a semisubmersible. To reveal the effects of mooring stiffness, two mooring systems were employed in the model tests and time-domain simulations. The 6-DOF motion responses and mooring tensions have been measured and the 3-DOF motions of fairleads were calculated as well. From the time series, trajectories and statistics information, the interactions between the freak wave and the semisubmersible have been demonstrated and the effects of mooring stiffness have been identified. The shortage of numerical simulations based on 3D potential flow theory is presented. Results show that the freak wave is likely to cause large horizontal motions for soft mooring system and to result in extremely large mooring tensions for tight mooring system. Therefore, the freak wave is a real threat for the marine structure, which needs to be carefully considered at design stage. 相似文献
7.
The dynamics of jacket supported offshore wind turbine (OWT) in earthquake environment is one of the progressing focuses in the renewable energy field. Soil-structure interaction (SSI) is a fundamental principle to analyze stability and safety of the structure. This study focuses on the performance of the multiple tuned mass damper (MTMD) in minimizing the dynamic responses of the structures objected to seismic loads combined with static wind and wave loads. Response surface methodology (RSM) has been applied to design the MTMD parameters. The analyses have been performed under two different boundary conditions: fixed base (without SSI) and flexible base (with SSI). Two vibration modes of the structure have been suppressed by multi-mode vibration control principle in both cases. The effectiveness of the MTMD in reducing the dynamic response of the structure is presented. The dynamic SSI plays an important role in the seismic behavior of the jacket supported OWT, especially resting on the soft soil deposit. Finally, it shows that excluding the SSI effect could be the reason of overestimating the MTMD performance. 相似文献
8.
《中国海洋工程》1988,(1)
- In this paper, a method for calculating the maximum dynamic loading during recovering a submersible from 30 m underwater to water surface has been deduced, and tests on the submersible model have also been made. The comparison between the experimental results and the calculated ones shows that there is a good coincidence. The method deduced in the paper can also be used to calculate the maximum tensile forces during the operation of lifting a weight nearby the water surface. 相似文献
9.
Hill Instability Analysis of TLP Tether Subjected to Combined Platform Surge and Heave Motions 总被引：1，自引：0，他引：1
This paper presents the Hill instability analysis of Tension keg Platform （TLP） tether in deep sea. The 2-D nonlinear beanl model, which is undergoing coupled axial and transverse vibrations, is applied. The governing equations are reduced to nonlinear Hill equation by use of the Galerkin＇ s method and the modes superposition principle. The Hill instability charted up to large parameters is obtained. An important parameter M is defined and can be expressed as the functions of tether length, the platform surge and heave motion amplitudes. Some example studies are performed for various envirotnnental conditions. The results demonstrate that the nonlinear coupling between the axial and transverse vibrations has a significant effect on the response of structure. It needs to be considered for the accurate dynamic analysis of long TI2 tether subjected to the combined platfolna surge and heave motions. 相似文献
10.
《中国海洋工程》1988,(2)
- The numerical method of coupled boundary integral equation and finite element has been used to compute the forces of wave diffraction and radiation on large two dimensional objects. Results consist of the drifting forces, added mass and damping coefficients for rectangular and circular bodies floating, submerged or anchored to the sea bottom. Discussion of the method and results has been given in detail. Because of its economy and accuracy, the method can be used successfully in many related problems where the domain of solution is infinite. The method can also be applied to three-dimensional problems. 相似文献
11.
鲣鱼是印度洋重要的金枪鱼种类之一，其资源丰度与海洋环境关系密切。本研究根据1980-2010年印度洋鲣鱼围网生产统计数据以及海洋环境与厄尔尼诺-南方涛动（ENSO）指数等，对印度洋鲣鱼围网资源渔场时空分布，以及厄尔尼诺年和拉尼娜年等不同尺度气候条件下鲣鱼资源渔场时空变动及其与海洋环境因子的关系进行分析。研究结果表明，1980-2010年印度洋鲣鱼围网渔获量基本保持不断增加的趋势，但CUPE值变化幅度较大，最低仅为0.68 t/d（1997年），最高达到1.58 t/d（2002年）。同时鲣鱼资源丰度（CPUE）与Ni?o3.4区指数存在显著的负相关关系，即厄尔尼诺年，鲣鱼CPUE 随之下降，拉尼娜年，CPUE 随之上升。ENSO现象对鲣鱼渔场时空分布也有显著影响，厄尔尼诺发生时，鲣鱼围网作业渔场重心会向东、向北移动，而拉尼娜年则向西、向南移动。 相似文献
12.
鲣Katsuwonus pelamis广泛分布于各大洋热带和亚热带海域,其中以中西太平洋资源量最为丰富。综合评价环境因子对鲣鱼资源量的影响,构建科学的资源预报模型可为我国可持续合理开发该鱼种提供参考。本研究利用1998—2013年中西太平洋渔获量数据,以单位捕捞努力量渔获量(CPUE)为资源相对丰度指标,利用灰色关联方法分析鲣鱼资源相对丰度与环境因子之间的关联度,选取合适的环境因子,并基于不同环境因子构建不同的灰色预测模型对鲣鱼资源相对丰度进行预测,比较选择最优模型。结果表明, 中西太平洋鲣鱼的产量逐年递增,而CPUE在年间有着较大的波动。灰色关联分析认为,海表面温度与CPUE的平均关联度最大,其次为Nino3.4区海表温度距平值,其他的环境因子与CPUE的关联度较小。基于多环境因子的预测模型中,包含所有因子(海表面温度、海表面高度、叶绿素质量浓度a和Nino3.4区海表温度距平值)的模型M1有着最佳的拟合效果,实际值与预测值的相对误差为6.475 2,相关系数为0.687 4;而基于单一环境因子的预测模型中,去除11月SST数据的模型S2有着最佳的拟合效果,实际值与预测值的相对误差为7.419 2,相关系数为0.791 0。相比多环境因子的预测模型,单一环境因子预测模型有着较高的稳定性,实际值与预测值直接相关性也较高,可以作为中西太平洋鲣鱼资源相对丰度预报的最优模型。 相似文献
13.
鲣是大洋中重要经济种类，主要分布于太平洋中西部海域，其渔场和资源丰度易受海洋环境因子影响。根据1995-2014年中西太平洋金枪鱼围网船队在主要作业海域（15°S~10°N，120°E~155°W）的生产数据，结合弱、中、强拉尼娜条件下的海表温度（SST）和海面高度（SSH）数据，运用算术平均法（AM）建立基于SST和SSH的栖息地指数综合模型。结果表明，在栖息地综合指数（HIS）大于0.6的海域，各拉尼娜时期作业比重均在60%以上。利用弱拉尼娜（2005年12月-2006年3月）、中拉尼娜（2011年10月-2012年3月）和强拉尼娜（2010年6月-2011年4月）数据进行模型验证，分析认为作业渔场主要分布在HSI大于0.6的海域，作业次数所占比重分别为53.9%、66.5%、63.6%。在中西太平洋区域，随着拉尼娜强度的增加，资源丰度上升，其渔场分布向东北和东南方向扩散。研究表明，基于SST和SSH各强度拉尼娜时期的栖息地模型均可较好预测中西太平洋鲣渔场，并为以后拉尼娜期间中心渔场的分析提供参考。 相似文献
14.
金枪鱼类是中西太平洋海域重要的经济鱼种，其中鲣产量约占到总产量的50%。本研究利用1995-2010年16年的中西太平洋（20°S~20°N，120°E~155°W）鲣围网生产统计数据和Niño3.4海区（5°S~5°N，120°~170°W）海表温度异常数据，对这16年鲣产量最高的十大渔区（5°×5°）进行时空格局分析，讨论渔场分布差异及CPUE与ENSO指数的关系。结果表明:16年间十大作业渔区主要分布在5°S~5°N、130°~175°E区域，这十大渔区产量占总产量的比重达47.5%，其中5°S~0°、155°~160°E，0°~5°N、130°~135°E，0°~5°N、135°~140°E及5°S~0°、160°~165°E等4个渔区产量占高产渔区产量的比重均超过10%，是中西太平洋重要的鲣产区。高产渔区的分布受海表温度影响较大，在厄尔尼诺时期，高产渔区分布明显偏东，主要分布在155°~180°E海域；在拉尼娜时期，高产渔区分布明显偏西，主要分布在130°~160°E海域。 相似文献
15.
中西太平洋金枪鱼围网技术及存在的问题 总被引：3，自引：0，他引：3
金枪鱼围网产量约占全球金枪鱼捕获量的70%,发展金枪鱼围网渔业具有广阔的前景.本文根据中鲁远洋渔业股份有限公司金枪鱼围网渔船的作业情况,分析了围网作业中的一些捕捞技术,并探讨了在发展该项目中存在的问题. 相似文献
16.
大西洋金枪鱼渔业现状分析 总被引：4，自引：0，他引：4
本文采用大西洋国际金抢鱼保护委员会ICCAT的报告和统计常设委员会（SCRS）数据库，统计分析了1978-2002年大西洋金抢鱼的渔获种类及渔具渔法。结果表明：按种类分黄鳍金枪鱼（占28％）、鲣鱼（22％）、长鳍金枪鱼（15％）、大眼金枪鱼（11％）、其他种类（8％）；按渔具分围网（42％）、延绳钓（29％）、饵钓（22％）、其它渔具（7％）。同时分析了不同海域的渔获种类、渔获量波动情况和原因。 相似文献
17.
《Marine Policy》2014
The use of drifting fish aggregating devices (FADs) has become the dominant practice in tropical tuna purse seine fishing. However, just as FADs can increase fishing efficiency, their use has been associated with several negative ecosystem impacts, and moves are being made to manage the use of FADs. In the evaluation of potential management options it is important to consider how fishers will respond to the introduction of control measures, which first requires an understanding of fishery and fleet dynamics. This paper addresses this need by characterising the past and present use of FADs in the Indian Ocean tropical tuna purse seine fishery. The paper describes historical trends in fishing practices, summarises spatiotemporal patterns in the use of FADs and establishes and attributes variation in FAD fishing strategies within the fleet. It also provides an overview of current FAD management policies in the Indian Ocean and examines the observed effects of existing measures on the behaviour of the purse seine fleet. Using this comprehensive understanding, the potential impact on the purse seine fleet of a number of plausible FAD management options are discussed and inferences are drawn for the future sustainability of tropical tuna purse seine fishing in the Indian Ocean. 相似文献
18.
采用2016—2017年中国印度洋围拖网生产数据和同期的海表温度、叶绿素、表层海流和海面高度数据, 绘制了阿拉伯海鲐鱼Scomber australasicus围网月平均单位捕捞努力量渔获量(CPUE)和环境因子空间叠加图, 分析鲐鱼渔场与海洋环境因子之间关系, 采用频次分析和经验累积分布函数计算鲐鱼渔场最适宜的海洋环境区间。结果表明, 该海域月平均CPUE呈现先减少后增加的趋势; 围网渔场渔汛主要在东北季风期间, 从10月到翌年3月; 作业渔场重心分布在59°—62°E、13°—17°N, 具有明显的月变化, 基本呈现西南移动趋势。空间上, CPUE 分布在西边界流速较大的海域右侧, 在海流最大值和最低值中间区域。在印度洋东北季风期间, 阿拉伯海围网鲐鱼渔场适宜海表温度在25~28℃; 叶绿素浓度在0.2~0.5mg·m -3; 表层海流在0.05~0.25m·s -1; 海表高度0.2~0.35m。 相似文献
19.
The simulation of the geometry of a tuna purse seine under current and drift of purse seiner 总被引：4，自引：0，他引：4
It was necessary to obtain a more practical interactive precise model of the three-dimensional (3-D) geometry during purse seine operations considering movements of fishing vessel and details of the sea condition. The changes in the shape of a purse seine from shooting to pursing during pelagic skipjack fishing was recorded in the Southwest Pacific Ocean by photographs of the scanning sonar with in situ measurements of water flow by a current meter. The modeling of 3-D geometry during purse seining was established using finite element methods, as resultant force vector from flow drag, buoyancy, sinking force, tension of pulling or pursing acting on net panels in connection with drift of fishing vessel with time elapsed from the start of shooting to the end of pursing. The simulation results were matched closely by field measurements as a heart-like shape in upper net near floatline and a water-drop shape in purse line following drift of ship towards inside net circle during pursing. This model of a purse seine can be extended to almost any kind of purse seine generating real fishing parameters and to modeling fish capture process. 相似文献
20.
中西太平洋金枪鱼围网渔业鲣鱼资源的时空分布 总被引：7，自引：0，他引：7
利用灰色关联度方法及渔业地理信息系统软件Marine Explorer4.0对1990~2001年中西太平洋金枪鱼围网渔业鲣鱼资源的时空变化进行了研究,结果表明,12年间中西太平洋鲣鱼产量的空间分布可归为3类:1990、1991、1995和1996年的为第一类,鲣鱼产量的主要分布区位于西部海域;1998、1999和2001年的为第二类,鲣鱼产量的主要分布区比第一类偏东20个经度;1992、1993、1994、1997和2000年的为第三类,鲣鱼产量的主要分布区的范围比前两类广。单位捕捞努力量的鲣鱼渔获量高分布区与产量空间分布区基本相似。灰色关联度的分析表明,12年中,1998、2000、1994、1995和1999年5年的鲣鱼资源丰度较高,1990、1991、1997和2001年4年的鲣鱼资源丰度较低,1996、1992和1993年3年的鲣鱼资源丰度处于中等水平。 相似文献