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1.
港口内靠码头系泊船运动的计算   总被引:11,自引:1,他引:11  
本文以英国南海岸处Shoreham港内系泊船为例,研究了港口内靠码头系泊船运动的数值计算问题。该船的实船实验和模型实验已经完成,为验证本文计算结果提供了依据。运动方程在时域内求解。在计算船体脉冲响应函数时,引入了船体阻尼系数在频率很低时的渐近表达式和一迭代算法。分析了港内共振波浪和其对船体的作用力。讨论了靠码头系泊船运动的非线性特征。计算结果与实验结果符合很好。  相似文献   

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3.
李志伟  肖洋  唐洪武 《海洋工程》2015,29(1):91-104
An elliptic jet and a square jet flowing into a counterflow with different jet-to-current velocity ratios are investigated by using realizable k–ε model. Some computed mean velocity and scalar features agree reasonably well with experimental measurements, and more features are obtained by analyzing the computed results. After fluid issues from a nozzle, it entrains ambient fluid, and its velocity and concentration on the centerline decay with the distance downstream from the potential core (l0). The decay ratio increases with the decreasing jet-to-current velocity ratio α. For an elliptic jet, the evolution of the excess velocity half-width b and the concentration half-width bc merely remains constant near the jet exit on major-axis plane while they increase linearly on the minor-axis plane. However, the half-widths on the major-axis and minor-axis plane become proportional to the axial distance downstream after equaling each other. For a square jet, b and bc increase linearly with the distance downstream from the jet exit, but the spread ratio is larger on the middle plane than that on the diagonal plane before they equal each other. The radial extent of the dividing streamline rs or the mixing boundary rsc increases linearly downstream, and decreases exponentially after reaching a peak at xb. The ratio on the minor-axis plane is larger than that on the major-axis plane for an elliptic jet. The characteristics are the same for the square jet. b, bc, rs, and rsc on two corresponding planes become equal to each other more rapidly for the square jet than for the elliptic jet, because the sharp corner of the square nozzle induces secondary structures that are more intense. The distributions of the excess axial velocity and scalar concentration exhibit self-similarity for either the elliptic jet or square jet in the region of l0 < x < xb. On the cross section, four counter-rotating pairs of vortices, which enhance the entrainment between the jet and counterflow, form at the four corners of the square jet or at the two ends of the major-axis plane of the elliptic jet. The recirculation pattern formed by these axial vortices is more complex for the square jet than that for the elliptic jet. The turbulent kinetic energy k have large value in the region near the jet exit and stagnation point. The maximum value of k for the square jet is larger than that of the elliptic jet near the jet exit. This results in the square jet mixing more strongly than the elliptic jet.  相似文献   

4.
提出一种基于序贯预测误差方法(SPE)的多层神经网络(MNN)的学习算法。经模拟计算,它比传统的基于最陡下降方法的误差反传(SDBEP)算法具有更好的收敛性能。并对这两种算法进行了模拟计算的比较.  相似文献   

5.
This paper deals with the study of moisture budget of the typhoon No. 7507. The results show that the mass convergence produced by divergent wind has made the maximum contribution to precipitation, especially at the lower level, accounting for about 70% of the total precipitation, and that the advection term of water vapor is very small. The vertical flux term is to transport water vapor from the lower level to the middle and upper levels, resulting in the increase of water vapor accumulation at these levels. Evaporation term also plays an important role in precipitation, accounting for about 13% of the total precipitation and 23% of the horizontal moisture convergence. The moisture of the typhoon comes mainly from its southern boundary and the secondary inflow of moisture is from its western or eastern boundary. All the inflow layers of these three boundaries are very deep, reaching up to 300 hPa, while the strongest inflow occurs below 700 hPa. In the northern boundary of the typhoon, we obtained that  相似文献   

6.
A 2-D time-domain numerical coupled model is developed to obtain an efficient method for nonlinear wave forces on a fixed box-shaped ship in a harbor.The domain is divided into an inner domain and an outer domain.The inner domain is the area beneath the ship and the flow is described by the simplified Euler equations.The other area is the outer domain and the flow is defined by the higher-order Boussinesq equations in order to consider the nonlinearity of the wave motions.Along the interface boundaries between the inner domain and the outer domain,the volume flux is assumed to be continuous and the wave pressures are equal.Relevant physical experiment is conducted to validate the present model.It is shown that the numerical results agree with the experimental data.Compared with the coupled model with the flow in the inner domain governed by the Laplace equation,the present coupled model is more efficient and its solution procedure is more simple,which is particularly useful for the study on the effect of the nonlinear wave forces on a fixed box-shaped ship in a large harbor.  相似文献   

7.
中国隆头鱼之一新属新种——尖尾新丝隆头鱼   总被引:1,自引:0,他引:1  
在过去几年的西沙群岛鱼类区系调查中,我们曾在西沙群岛的东岛和永兴岛附近水域,先后三次采到5尾前所未曾见过的隆头鱼类标本,经过比较研究后,认为是一新属、新种,定名为“尖尾新丝隆头鱼”,(Neocirrhilabrus oxyurus gen. et sp. nov.)现描述如下:  相似文献   

8.
本文对J.Maynard Smith提出的物种竞争模式: x=x(a-bx-cy-kxy) y=y(e-fx-gy-lxy)作了定性分析,并给出两物种共存或其中任一物种死亡,而另一物种趋于确定值的条件。  相似文献   

9.
An edge wave is a kind of surface gravity wave basically travelling along a shoaling beach. Based on the periodic assumption in the longshore direction, a second order ordinary differential equation is obtained for numerical simulation of the cross-shore surface elevation. Given parameters at the shoreline, a cross-shore elevation profile is obtained through integration with fourth-order Runge-Kutta technique. For a compound slope, a longshore wavenumber is obtained by following a geometrical approach and solving a transcendental equation with an asymptotic method. Numerical results on uniform and compound sloping beaches with different wave periods, slope angles, modes and turning point positions are presented. Some special scenarios, which cannot be predicted by analytical models are also discussed.  相似文献   

10.
利用硫酸铵分级盐析、DEAE-纤维素阴离子交换层析、Sephadex G-75凝胶层析法对由海洋细菌FE92-8分泌的纤维蛋白溶酶进行了分离纯化,结果得到SDS-聚丙烯酰胺凝胶电泳单一区带。性质研究发现,该酶分子量为12.6kD,等电点为7.45,琼脂糖-纤维蛋白平板法测得该酶作用的最适温度为50℃,最适pH为8.0,在37℃,pH为8.0的情况下表现出很好的稳定性,温度起来50℃热稳定性较差,在碱性环境中稳定性较在酸性环境中稳定性强,阴性平板和阳性平板对比实验发现,该酶只有纤溶活性而无激酶活性,体外实验发现,该酶具有快速溶解血栓的能力。  相似文献   

11.
A New Model for Ice Forces on A Conical Structure   总被引:1,自引:0,他引:1  
The ice force is an important factor to be taken into account for offshore structures in cold regions, and the calculation method of the ice force is meaningful for the offshore structure design. The cone is now used as an optimal ice-resistant structure because it can cause bending failure of the ice sheet. The interaction between an ice sheet and a conical structure is studied in this paper and Croasdale‘s model is modified based on field observations. The newly built model separates the ice sheet into the emersed part and the floating part, and the equilibrium analyses are canied out respectively. The bending moment distribution of the ice sheet is analyzed for the determination of the position of bending failure, which serves as a supplementary restraint. The analytic solution of the ice foree on a conical structure is obtained it is verified with the experimental data of previous researches.  相似文献   

12.
This is a numerical study on the time development of surface waves generated by a submerged body moving steadily in a two-layer fluid system, in which a layer of water is underlain by a layer of viscous mud. The fully nonlinear Navier-Stokes equations are solved on FLUENT with the Volume-of-Fluid (VOF) multiphase scheme in order to simulate the free surface waves as well as the water-mud interface waves as functions of time. The numerical model is validated by mimicking a reported experiment in a one-layer ...  相似文献   

13.
Field measurement of waves and wave pressure in a given harbour were carried out in the years 1973 and 1977 and then the statistical analysis was made. Based on this analysis and the linear wave theory some problems concerning the total pressure spectrum and the total pressure crest value and trough value are discussed, and the method of calculating these quantities is given.  相似文献   

14.
以Ba为指标反演海洋古生产力的研究进展   总被引:9,自引:0,他引:9  
海洋沉积物中的生源Ba通量与有机碳通量有着惊人的相关性,因此Ba很适合作为古生产力的指标。概述了Ba与生产力的相关性原理.对反演过程中3个主要影响因子(沉积环境、海水中的Ba浓度、沉积物堆积速率)进行了探讨.分析了计算模型并对模型发展方向作了预测。认为生源Ba形成机制和沉积环境中干扰因素扣除将是今后研究的重点.指出在我国开展以Ba为指标的古生产力研究对古海洋生态环境研究有重要意义。  相似文献   

15.
用fKdV模式方程对单层二维表面波进行直接的数值研究。计算得出,在共振区域先锋孤立子的生成与T、Y.Wu(吴耀祖)及S.J.Lee等人的结果相同。在共振点与超临界转向点之间,对每一个Fr数存在初始不稳定的单峰孤立子,其振幅随时间增加。当Fr数接近共振区时,初始孤立子分裂成先峰孤立子,即先峰孤立子生成是占优的。当Fr接近超临界转向点时,这类初始不稳定孤立子最终破碎。当Fr超过超临界转向点时,存在一类稳定的超临界孤立子,其振幅不随时间变化,但是它得自时间相关方程。这类孤立子位于驱动力上方,它的振幅随Fr的增加而减少.由于它不同于自由KdV孤立子,因此本文称之为超临界驻定孤立子。  相似文献   

16.
根据基本的扩散方程,以污染物质输入量为已知条件,给出了一种近区稀释的半解析解。该半解析解摆脱了流速是单向的、持续的和定常的条件限制,反映了近区稀释在以潮流场为背景场的状态下,随时间的可变性。  相似文献   

17.
《Marine Policy》2005,29(2):139-146
Regarding the regime of military and intelligence gathering activities in the EEZ, China argues that the freedoms of navigation and overflight in the EEZ have certain restrictions including that the activity must be peaceful and not threaten to use force against the coastal State. This includes military surveys, military maneuvers, and military reconnaissance which are a form of battlefield preparation. These activities are also subject to due regard for the rights of the coastal State. China also argues that there are serious shortcomings regarding the regime of marine scientific research (MSR) in the EEZ and that marine surveys or military surveys carried out by MSR platforms require the consent of the coastal State.  相似文献   

18.
《Marine Policy》2005,29(2):157-161
The adoption of the EEZ in the 1982 UNCLOS represents the culmination of an effort by some parts of the international community to separate “jurisdiction” over the natural resources in offshore waters from the “sovereignty” manifest in the territorial sea. It is clear that the EEZ is a zone that is neither territorial waters nor wholly high-seas. It is also a zone in which competencies are balanced between the need of coastal States to have sufficient authority to exploit and manage their economic resources and the need of all other States to retain high-seas navigation and communications freedoms and uses related to such freedoms. From South Korea's perspective, the EEZ is a sui generic zone in which military and intelligence activities are limited or not allowed without the consent of the coastal State. This is equally applicable in peace and war. Although several States stress that Article 58 of the 1982 UNCLOS permits such activities, increasing EW and IW capabilities may result in reinterpretation of certain provisions of the 1982 UNCLOS.  相似文献   

19.
A giant piston-corer   总被引:1,自引:0,他引:1  
A new large piston-coring device utilizing well-casing pipe 14 cm (o.d.), 11 cm (i.d.) has obtained cores over 20 m in length in water depths of 100 to 5000 m. Recovery ratios range from 0·76 to 0·87. Penetration varies between 24 and 29 m with a total core weight of 3200–4000 kg and 2 to 3 m of free fall.  相似文献   

20.
一种浮力式盐度计   总被引:4,自引:0,他引:4  
于1995年综合应用液体浮力←→密度←→盐度←→溶液性质等原理研制浮力式盐度计,该盐度计具有操作简单,测试快速、不用电源和试剂、使用前无需标准海水标定、测试值不受样品成分变化影响的特点;其测增精度可达克纽森滴定法,适用于一般工业化生产,水产养殖、港湾河口区调查等.  相似文献   

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