运动目标及其可视化方法研究

在分析运动目标的内涵、基本特征及分类的基础上,探讨了运动目标的可视化表达方法。针对传统可视化技术在表达运动目标方面存在的不足,提出了一种改进型的可视化实现技术——基于显示模型技术的运动目标可视化实现方法。     

Estimation of the responses of axisymmetric bodies in spread irregular waves

A method is presented of estimating the responses of axisymmetric bodies floating in spread irregular seas, using a Laplace transfer-function formulation of a floating body time-domain model. A general-case spread-wave model is formulated, using separate wave excitation transfer functions, and a simplification of this approach is proposed, reducing both model complexity and computation time. Responses are computed using both approaches and a comparison made to assess the circumstances in which the simplified approach may be used effectively. The results are also interpreted to highlight the implications of using an equivalent unidirectional wave as an approximation to a spread wave.     

Water surface resonance in the L-shaped channel of seawater exchange breakwater

The resonance period of the L-shaped channel in the caisson is predicted analytically for the seawater exchange breakwater of “Applicability Study of the Seawater Exchange Breakwater (1). Korea Ministry of Maritime Affairs and Fisheries (in Korean) (1999a)”. Hydraulic experiments are conducted for a composite breakwater with a rear reservoir that is one of the seawater exchange breakwaters developed by them. For regular waves, the water surface elevation in the channel and the flow rate through the breakwater are measured. For irregular waves, the flow rate through the breakwater and the reflection coefficient on the breakwater are measured. The resonant maximum values in both the surface elevation and the flow rate, and the resonant minimum values in the reflection coefficient are all at wave periods slightly longer than analytically predicted ones. The measured resonance period for irregular waves is closer to the predicted one than for regular waves. If the resonance period of the L-shaped channel is fitted to the dominant period of incident waves, there would be high efficiency of seawater exchange between inside and outside the harbor.     

Numerical Simulation and Experimental Investigation on Performance of the Wells Turbine in Irregular Oscillating Flow

The Wells turbine is an axial-flow air-turbine designed to extract energy from ocean waves. An important consideration is the self-starting capability of the Wells turbine, a phenomenon encountered where the turbine accelerate by itself up to a certain speed for the best turbine performance. In order to clarify the self-starting characteristic and running performance of the Wells turbine in an irregular oscillating flow, a numerical simulation process is established in this paper on the rational assumption of quasi-steady flow conditions. Both self-starting characteristics and running performance are obtained through the numerical simulation and subsequently compared with the experimental data achieved on a computer-controlled oscillating flow test rig which could realize some irregular oscillating flow according to the specified spectrum. Results show that the self-starting time decreases with the increase of the significant wave height and the mean frequency of the irregular oscillating flow. Therefor     

Three-Dimensional Model Test for Port Engineering with Multi-Directional Waves

-The necessity of using irregular waves, especially multi- directional waves to conduct three-dimensional model tests for port engineering and the test method are described in this paper through an example of model test for a port. The test results show that a deep navigation channel has a large effect on the waves in front of the breakwater near the port entrance and on the wave condition in the port.     

Experimental and Numerical Study of Wave-Induced Long-Shore Currents on A Mild Slope Beach

1.Introduction Long shorecurrenthasbecomethesubjectofextensiveworldwideresearchformanyyears.The purposeofthestudyistounderstandandpredicttheprocessesofsedimenttransport,shorelineevolu tionandpollutanttransportinthenear shorezoneundertheactionofwaves.Goda(2001)regarded thesuspendedsedimentastheprincipalloadinsedimenttransportandtheeffectoflong shorecurrents wasemphasized.Theeffectofwavesonpollutanttransportwasstudiedbynumericalmodelandfield experiment(TaoandHan,2002;Rodriguezetal.,1995),andth…     

Nonlinear Dynamic Analysis of Flexible Marine-Risers

A nonlinear dynamic analysis model is estabilished on the basis of "lumped mass" approach, which takes the influence of the fluid flow within the pipe into consideration. Numerical results are compared with the published works, and the effects of internal fluid flow, internal pressure, dyanmics as well as the nonlinear characteristics on the behavior of flexible risers are discussed. From this work, some useful conclusions are drawn.     

近岸区直墙波浪力的模拟

在水槽中进行了几种不同坡度的斜坡平台上规则波作用下直墙波浪力试验，系统分析了直墙上相对最大压强和相对最大总力，给出了它们之间的比较关系。还进行了不同坡度的不规则波模型试验，并讨论了波浪力之间的特性。结果表明采用1：10、1：15的斜坡与平台相结合的试验室模拟，可得到与平底地形相近的直墙波浪力。     

斜向不规则波入、反射波分离的实验研究

斜向入射的不规则波在海岸结构物前发生反射形成入、反射波共存的波浪场,对这种物理场的入、反射波的分离是海岸工程研究的一个重要课题.改进了一种可用于斜向入射的不规则波分离的两点法,使得测波阵列的两波高仪可布置在结构物前任何方向上.将此方法应用于三维波浪水池的物理模型试验研究,试验了不同的两波高仪的组合、不同的基床高度、不同的入射方向和不同的波浪要素等各种条件对分离结果的影响,结果表明,各种情况在满足非奇异条件下可得到较好的分离结果.该方法计算简便,可以给出较准确的反射系数和入、反射波的频谱.     

Hydrodynamic Coefficients for Grouping Piles Under the Action of Irregular Waves

-The hydrodynamic coefficients for each of two piles and three piles in both side-by-side arrangement and tandem arrangement under the action of irregular waves are experimentally investigated. These coefficients vary with the KC number, the relative pile spacing, the number of piles and the pile location, and their relationships are presented in this paper. They can be used in Morison Equation and other equations to calculate directly the in-line wave forces and the transverse forces on each pile in array.