Analytical Research on Wave Diffraction on Arc-Shaped Bottom-Mounted Perforated Breakwaters

An analytical method is developed to study wave diffraction on arc-shaped and bottom-mounted perforated breakwaters.The breakwater is assumed to be rigid,thin,vertical,immovable and located in water of constant depth.The fluid domain is divided into two regions by imaginary interface.The velocity potential in each region is expanded by eigenfunctions.By satisfying the continuity of pressure and normal velocity across the imaginary fluid interface,a set of linear algebraic equations can be obtained to determine the unknown coefficients of eigenfunctions.Numerical results,in the form of contour maps of the relative wave amplitude around the breakwater,are presented for a range of wave and breakwater parameters.Results show that the wave diffraction on the arc-shaped and bottom-mounted perforated breakwater is related to the incident wavelength and the porosity of the breakwater.The porosity of the perforated breakwater may have great effect on the diffracted field.     

Diffraction of Water Waves by A Vertically Floating Cylinder in A Two-Layer Fluid

In this paper, the diffraction of water waves by a vertically floating cylinder in a two-layer fluid of a finite depth is studied. Analytical expressions for the hydrodynamic loads on the vertically floating cylinder are obtained by use of the method of eigenfunction expansions. The hydrodynamic loads on the vertically floating cylinder in a two-layer fluid inelude not only the surge, heave and pitch exciting forces due to the incident wave of the surface-wave mode, but also those due to the incident wave of the internal-wave mode. This is different from the case of a homogenous fluid. Some given examples show that, for a two-layer fluid system with a small density difference, the hydrodynamic loads for the surface-wave mode do not differ significantly from those due to surface waves in a single-layer fluid, but the hydrodynamic loads for the internal-wave mode are important over a wide range of frequencies. Moreover, also considered are the free surface and interface elevations generated by the diffraction wave due to the incident wave of the surface-wave and interhal-wave modes, and transfer of energy between modes.     

Domain decomposition and matching for time-domain analysis of motions of ships advancing in head sea

A domain decomposition and matching method in the time-domain is outlined for simulating the motions of ships advancing in waves. The flow field is decomposed into inner and outer domains by an imaginary control surface, and the Rankine source method is applied to the inner domain while the transient Green function method is used in the outer domain. Two initial boundary value problems are matched on the control surface. The corresponding numerical codes are developed, and the added masses, wave exciting forces and ship motions advancing in head sea for Series 60 ship and S175 containership, are presented and verified. A good agreement has been obtained when the numerical results are compared with the experimental data and other references. It shows that the present method is more efficient because of the panel discretization only in the inner domain during the numerical calculation, and good numerical stability is proved to avoid divergence problem regarding ships with flare.     

流体动力干扰对桩柱矩阵阵列波浪力的影响

随着超大型海洋结构物的设计和研究日益受到重视,研究多物体之间的流体动力干扰特性显得十分必要。用波动源在截面周线上分布的方法,就垂直桩柱间三维流体动力干扰对波浪力的影响进行了系统的研究,不仅可得到单行柱列的流体动力干扰力学机理的新特性,而且对多行桩柱阵列的研究也取得了若干新的发现：多行柱柱阵列的遮蔽作用强于单行的;无论是单行还是多行柱列,其流体动力干扰特性存在一个十分敏感的来波频域,在此区域内,力的幅值会大大超过其他频域的受力,而且桩柱阵列与交错阵列的力学特性也有所不同。这对超大型海洋结构物的设计有着重要的指导意义。     

平台脚柱的波浪作用力

波浪作用力是海洋工程结构物设计和研究中需要考虑的重要因素之一。由于平台脚柱的轴对称性,整个流场可划分成若干予域,子域中的迷度势可用在形式上以其特征函数展开式表示。通过这些速度势在它们的公共边界上的匹配关系,流场中的速度势可唯一地确定。本文提供了用特征函数匹配求解平台脚柱波浪作用力的计算方法。从计算结果与三维源汇分布法的计算结果的比较来看,本文的计算方法提洪的结果相当精确,耗费的计算机时则大为降低。     

潜体绕流及远场声特性分析

首先采用SST（shear-stress transport）k-ω两方程湍流模型求解了潜体三维非定常粘性流场,然后基于Lighthill声类比理论,对潜体流噪声的远场特性进行了数值分析,并探讨了攻角的影响。研究结果显示,基于所研究的潜体外形,潜体在舷侧及深度等正横方向上的声辐射显著高于潜体在艏、艉等轴向上的声辐射,攻角的存在使声辐射增大。     

甘肃文县震旦纪锰矿石中古菌藻的发现及其意义

1985——1987年,笔者在甘肃文县地区从事《甘肃文县石坊——沟岭子一带震旦纪锰磷成矿条件及找矿方向》专题研究时,经成都地院帅德权老师应用扫描电子显微镜及反光显微镜,在锰矿石中发现了许多矿化的小圆球体、椭圆球体及各种不同形态的集合体。它们是矿化了的细球菌、双联球菌、链球菌及各种不同形态的菌落结构。另外,在矿石中还发现有大量微古植物化石,经成都地质矿产所王福星鉴定,主要有厚缘小球藻、小球藻、瘤面球形藻、穴面形藻及梭形藻等。研究菌藻的生物沉积作用并用之于成矿环境分析及探讨锰矿的形成作用,对研究沉积锰矿床的成因理论、成矿规律及找矿方向等都有很重要的意义。     

非线性波传播的新型数值模拟模型及其实验验证

以一种新型的Boussinesq型方程为控制方程组,采用五阶Runge-Kutta-England格式离散时间积分,采用七点差分格式离散空间导数,并通过采用恰当的出流边界条件,从而建立了非线性波传播的新型数值模拟模型.通过对均匀水深水域内波浪传播的数值模拟说明,模型能较好地模拟大水深水域和强非线性波的传播.通过设置不同的入射波参数来进行潜堤地形上波浪传播的物理模型实验,并将数值解与物理模型实验结果进行了比较.     

Numerical Treatments and Applications of the 3D Transient Green Function

How to evaluate time-domain Green function and its gradients efficiently is the key problem to analyze ship hydrodynamics in time domain.Based on the Bessel function,an Ordinary Differential Equation(ODE)was derived for time-domain Green function and its gradients in this paper.A new efficient calculation method based on solving ODE is proposed.It has been demonstrated by the numerical calculation that this method can improve the precision of the time-domain Green function.Numerical research indicates that it is efficient to solve the hydrodynamic problems.     

关于DAWSON方法中网格划分的研究

在CFD中,网格的划分有时是一个很重要的问题。在势流理论的DAWSON方法中,有一套生成网格的基本方法,但初值的选择是人为的,因此,如何选择一个合理的初值乃是一个关键的问题。有鉴于此,本文就WIGLEY船型,基于正交设计原理,设计了数值试验方案,研究了各种不同的初值对波形图和源强分布图以及兴波阻力的影响,并据此给出了一个选择合适初值的方法。