Time-domain hydrodynamic analysis of pontoon-plate floating breakwater

The hydrodynamic behaviors of a floating breakwater consisting of a rectangular pontoon and horizontal plates are studied theoretically. The fluid motion is idealized as two-dimensional linear potential flow. The motions of the floating breakwater are assumed to be two-dimensional in sway, heave, and roll. The solution to the fluid motion is derived by transforming the governing differential equation into the integral equation on the boundary in time domain with the Green’s function method. The motion equations of the floating breakwater are established and solved with the fourth-order Runge-Kutta method to obtain the displacement and velocity of the breakwater. The mooring forces are computed with the static method. The computational results of the wave transmission coefficient, the motion responses, and the mooring forces of the pontoon-plate floating breakwater are given. It is indicated that the relative width of the pontoon is an important factor influencing the wave transmission coefficient of the floating breakwater. The transmission coefficient decreases obviously as the relative width of the pontoon increases. The horizontal plates help to reduce the wave transmission over the floating breakwater. The motion responses and the mooring forces of the pontoon-plate floating breakwater are less than those of the pontoon floating breakwater. The mooring force at the offshore side is larger than that at the onshore side.     

基于N-S方程的波浪与可渗防波堤相互作用的数值模拟

采用N-S方程作为波浪场和孔隙流域的控制方程,应用有限差分方法对控制方程进行离散求解,采用VOF方法跟踪自由表面,反复迭代求解得到整个流域的压力场和速度场,并分析堤后渗透波高随入射波高、入射波周期的变化规律。最后结合波浪水槽物理模型试验验证本文所建立的数学模型,验证结果表明,此文所建立的数学模型可较好的模拟波浪与可渗防波堤的相互作用。     

Working mechanism and numerical simulation of assembly coastal building techniques

A new coastal technique, named as assembly coastal building, was introduced. The main concept of the technique was the assembling components which could be combined and locked together to form a large caisson. The assembly coastal building technique was used in a sea access road in Zhuanghai 4X1 well, Dagang Oilfield. The design plans and in-situ tests in the sea access road project were introduced in detail. According to the Zhuanghai project, the numerical simulation method of assembly coastal building technique was proposed. 2D numerical simulations were performed in FLAC to analyze the displacement and stability of the technique in the construction process and post-construction period. The settlement calculated is close to the in-situ results, which proves that the proposed numerical method is reasonable. Results show that the assembly coastal building technique has large safety factor under the gravity loading and wave loadings.     

抛石防波堤堤内波浪运动的数值模拟

将抛石防波堤认为离散介质结构,根据抛石防波堤内块体随机堆放的特点生成断面,对块体间的孔隙域划分网格。基于二维粘性不可压缩流体的N-S方程和流体自由表面处理的VOF方法,建立了波浪作用下堤身内部和前后流场的有限元数值模拟模型,对堤内的波浪运动进行了数值模拟。数值计算结果与波浪水槽模型实验结果基本吻合。对不同孔隙率和块体粒径的抛石堤计算结果表明,抛石堤内的波浪场受到很多参数的影响,孔隙率越大波长越长透射系数也越大,块体上的受力随着防波堤孔隙率以及块体平均半径的增加而减小。     

新型桶式基础防波堤下沉分析及其对稳定性的影响

鉴于新型桶式基础防波堤下沉过程的复杂性,单纯少量的下沉监测并不能全面、细致地反映这一过程。通过对桶体的简化处理,借鉴静压桩的下沉模拟方法,采用ABAQUS有限元软件对桶体的下沉挤土效应进行了模拟分析。通过分析发现,受桶体下沉影响,桶壁附近土体主要受到了桶壁水平挤压作用、紧靠桶壁的竖向挤压及摩擦作用及两桶壁之间盖板的竖向挤压作用。受几种作用的影响,桶壁附近的土体变形可分为紧靠桶壁的下沉区域、离桶壁稍远范围内的相对隆起区及两桶壁之间顶部的下压变形区,而且土体的这些变形决定了桶壁附近土体复杂的应力变化。在挤土效应模拟的基础上,进一步分析了考虑挤土效应对桶体稳定性的影响,挤土效应可增加桶体的稳定性。     

孤立波翻越防波堤流动的湍流数值模拟

应用湍流数学模型和流体体积法模拟孤立波翻越防波堤的流动和自由表面变化。数模成功地再现了波浪涌顶和喷射、射流入水、自由表面破碎和漩涡产生等复杂流动过程,并获得了孤立波翻越防波堤时的压力分布。     

Floating forest: A novel breakwater-windbreak structure against wind and wave hazards

A novel floating breakwater-windbreak structure (floating forest) has been designed for the protection of vulnerable coastal areas from extreme wind and wave loadings during storm conditions. The modular arch-shaped concrete structure is positioned perpendicularly to the direction of the prevailing wave and wind. The structure below the water surface acts as a porous breakwater with wave scattering capability. An array of tubular columns on the sloping deck of the breakwater act as an artificial forest-type windbreak. A feasibility study involving hydrodynamic and aerodynamic analyses has been performed, focusing on its capability in reducing wave heights and wind speeds in the lee side. The study shows that the proposed 1 km long floating forest is able to shelter a lee area that stretches up to 600 m, with 40%–60% wave energy reduction and 10%–80% peak wind speed reduction.     

防波堤稳定性的滑移控制

提出了利用防波堤的滑移控制防波堤对破碎波动力响应的概念,建立了破碎波—防波堤—地基相互作用的振动—滑移运动分析模型,对破碎波冲击作用下防波堤的振动—滑移运动过程进行了模拟,并对滑移控制防波堤的滑移力和倾覆力矩的效果进行了分析。     

气幕防波堤消波性能影响因素数值模拟研究

为研究气幕防波堤消波性能影响因素,将空气和水组成的两相流体处理为变密度单流体,通过UDF在连续方程中添加质量源项和动量方程中添加动量源项建立了气幕防波堤的数学模型,并将数值模拟结果与试验结果进行对比分析,二者具有较好的一致性,验证了气幕防波堤数学模型建立的合理性。以此为基础,对影响气幕防波堤消波性能的因素如入射波高、管道淹没深度进行了数值模拟计算,并通过分析、比较得出相关结论。这些结论对气幕防波堤的实际工程设计、施工等具有一定参考价值和指导意义。     

WAVE DIFFRACTION ON ARC-SHAPED BOTTOM-MOUNTED BREAKWATERS

1. INTRODUCTION Various types of breakwaters are common coastal structures to shelter harbors and s mall crafts fromthe direct attack of waves . Of these , the arc-shaped bottom-mounted breakwater is com- mon. This type of breakwaters , whose horizontal section is an arc shape ,is usually situated on the seabed and extended to above the water surface . Many researchers have performed a variety of studies on the wave diffraction performance of many kinds of breakwaters . Penney and Price …