网格锚定单体碟形网箱的水动力特性研究

目前碟形网箱在我国并未得到广泛的推广应用,但其良好的抗流抗变形能力和可沉降特点使其在大风大浪水流湍急的深海水域有着不可替代的作用。如能在深水碟形网箱的基础上,开发出具有自主知识产权的深水网箱,必将对我国的养殖业产生重大的影响。本文基于凝集参数法,利用Orca Flex软件建立网格锚定的深水碟形网箱模型,并进行了多海况下的数值计算。结果表明,波流联合作用下,对锚绳张力影响最大的为海流流速,其次为波高,周期对张力的影响并不明显;锚绳最大张力并非出现在入射波与流速同向的情况下,而是发生在两者存在某一夹角时;浮环最大倾角随流速和波高线性增大,随着波浪周期增大而减小;此外,下沉能明显改善网箱系统和锚绳的受力。     

碟形网箱水动力特性的研究

根据物模实验得到碟形网箱在不同海况条件下的受力并给出了其估算方法和公式及其相关系数的取值,同时总结了碟形网箱的运动特性。     

圆形重力式网箱阻力性能研究

采用网箱模型试验 ,对周长 5 0 m,深 8m的 HDPE双管圆形重力式网箱 ,在不同配重、网片规格和流速条件下的阻力性能进行研究。结果表明 ,在 2 .5 kn的相对流速范围内 ,网箱的整体阻力在 75 0 0 kg以内 ;在网箱整体阻力中 ,框架及重锤阻力所占比重较小 ,而网箱箱体阻力占近90 %。不同重锤配重的网箱 ,其整体阻力与流速均呈幂函数关系 F=a Vb,网箱重锤配重增加 ,网箱阻力也随之增大 ,而重锤配重变化对网箱阻力的影响程度又随流速的增加而减小     

重力式网箱数值模拟时波浪理论选择

针对重力式网箱数值模拟中波浪理论选择问题进行了专门的分析与讨论。在数值模型中分别采用线性波浪理论和斯托克斯五阶波浪理论,对重力式网箱的主要部件浮架系统和网衣系统进行模拟。通过将模拟结果与试验结果比较分析选取两种不同波浪理论对模拟结果的影响。分析结果认为在相对水深大于0.18情况下,应用线性波浪理论基本可以准确地模拟重力式网箱波浪作用下的运动和受力。     

钙质土中重力串锚水平承载力特性有限元研究

目前没有规范给出串锚的水平承载力计算公式,为了利用有限元法研究串锚水平承载力特性,采用相关理论计算以及室内试验的方法来验证有限元法模拟计算的可靠性。实践证明,有限元法具有较高的计算精度。利用有限元分析软件ABAQUS建立了串锚-土体模型,模拟串锚在水平荷载作用下破坏过程,研究了串锚在水平荷载作用下破坏机理,从而得到了串锚水平承载力特性。在相同的工况条件下,串锚的水平承载力与其锚链长度有关,在一定范围内,增加锚链的长度可以提高串锚的水平承载力;串锚的水平承载力不是相应的单个锚的水平承载力相加,其水平承载力小于相应的单个锚水平承载力之和,在进行串锚水平承载力设计计算时应给与相应的考虑。     

基于锚杆体系的重力式海上风电基础结构受力特性分析

文章以某风电场项目为背景,应用预应力锚杆对传统重力式海上风电基础结构进行优化,组成一种基于锚杆体系的重力式海上风电基础型式。采用ABAQUS软件对锚杆重力式基础结构进行受力分析,研究在正常工况和极端工况两种荷载条件下,结构的位移、应力变化情况以及地基的破坏形式。结果表明,预应力锚杆结构能够有效减小重力式海上风电基础在正常和极端受力工况下的水平位移、转角和沉降量,同时改变地基的破坏形式,有效提升结构的整体稳定性,该结构可为今后重力式海上风电基础的应用优化发展提供一定的参考。     

圆柱形沉浮式深海养殖网箱的受力分析

应用一系列力学关系，研究了深海圆柱形沉浮式养殖网箱所承受的波浪力情况。导出深海沉浮式养殖网箱的运动方程，并给出数值计算。在网箱波浪力的研究中采用绕射理论和Morison方程，讨论了在波高、波长及周期变化下水动力的变化趋势，得出网箱所受到的水平波浪力远大于竖直波浪力，波高的变化对波浪力的影响最大的结论，为深海网箱的设计校核提供1种参考方法。     

锚式采泥器的简介

锚式采泥器的简介徐学仁，高炳森（国家海洋环境监测中心大连）１引言随着我国海洋倾废管理工作的日益法制化和科学化。沉积物监测也显得非常重要，为了保证倾废法的执行和科学管理的裁决，不但要有一套沉积物分析的准确方法，还需要一种现场上科学地、方便地、快速地采样...     

水流条件下单点系泊不同结构“钻石型”重力式网箱的水动力特性数值模拟

目前深远海网箱养殖已成为我国海水鱼类养殖的一个重要方向,为获得适合于深远海养殖的最优网箱结构,本文利用数值模拟方法,对投放于黄海冷水团的"钻石型"网箱箱体设计了5种结构方案(方案1～方案5),进行水动力特性数值模拟,分析箱体结构的中部水平漂移、底部水平漂移以及网箱阻力等特性变化。研究表明,在流速为1m/s时,网箱中部水平漂移优化效果好的依次为方案5(减少30.59%)和方案2(减少20.23%),底部水平漂移优化效果好的依次为方案2(减少37.33%)和方案5(减少22.39%),网箱阻力优化效果好的依次为方案5(减少12.98%)和方案4(减少9.15%)。研究结果表明,采用刚性底框、方形网目,中部增加刚性圆环,网箱形状为上大下小的圆台形,有利于减小网箱的横向位移,降低网箱的阻力。研究结果可为深远海重力式网箱设计提供技术参考。     

Fundamental analysis of deep sea mooring line in static equilibrium

The integrated equations of deep sea mooring lines in static equilibrium under consideration of gravity force and line elongation are obtained. The most useful forms of the equations for designing deep sea mooring system are those in which horizontal displacement and horizontal and vertical components of tension are obtained as functions of line length, water depth, critical tension and unit weight of line.When the dynamic simulation of a buoy system is carried out, line tensions acting on the buoy should be represented as a linear function of displacement. Therefore the linearisation method is introduced by use of linearisation coefficient matrix. Translation formulae for the matrix from two to three dimensions is also presented.The influence of line elongation on the horizontal component of tension in a taut mooring condition is important, therefore the elongation of stretched deep sea mooring line must be considered carefully. Also, the scaling law under consideration of line elongation in static equilibrium, which is necessary in estimation from a small sized experiment, is discussed.     

浪流作用下系泊船舶撞击力和系缆力试验研究

以某25万吨矿石码头工程为例,分别进行了单流、单浪和浪流共同作用下,系泊船舶撞击力和系缆力试验。研究了不同水位、不同船舶载度、不同浪流夹角,单流、单浪和浪流共同作用时对船舶撞击力和系缆力的影响。分析了该码头工程护舷和缆绳的布置情况,为工程设计提供了依据。     

绷紧式系泊缆冲击张力特性研究

采用集中质量法研究了绷紧式系泊系统中系缆由于松弛-张紧过程产生的冲击张力。建立系泊缆绳离散的集中质量模型,对其独立单元进行受力分析并建立了单元的运动方程。给定缆绳上端点简谐激励,通过Ansys中的Aqwa模块,分析了缆绳的运动响应;针对缆绳运动响应过程中的三种状态进行了模拟计算,探讨了冲击张力产生的条件;研究了缆绳初始预张力、上端点激励幅值和频率、拖曳力系数、弹性模量以及单位长度质量对动态张力的影响。研究结果表明:这些影响因素不仅会影响缆绳动态张力的大小,也会对缆绳中的冲击张力产生一定的影响。     

海底对系缆运动及张力影响研究

对系缆运动及张力进行分析,并考虑海底对系缆的影响。采用细长弹性杆单元模拟系缆微段,建立系缆运动控制方程,采用有限元法对其进行离散,将海底弹性和阻尼作用力添加到离散控制方程中。利用牛顿法和Newmark-β法对离散后的系缆非线性运动方程组进行数值求解。模拟长600 m的系缆顶端受到垂向正弦激励时的运动,分别求得考虑和不考虑海底作用时系缆运动响应和动态张力。通过对比系缆的运动、速度和动态张力结果,发现海底的弹性阻尼作用对系缆的运动及张力特性有极大影响。上述研究工作为计算海底对系缆的作用力提供了新方法。     

Assessment of the effect of mooring systems on the horizontal motions with an equivalent force to model

The present work was carried out to assess the performance of an equivalent force model for the rapid analysis of mooring lines subject to horizontal motions. The verification is performed for cases of practical interest. Due to the very distinct behaviour of slack, moderately slack and taught moorings, these are analysed separately and the variation in the model coefficients is justified. It is shown that the methodology provides reasonable estimates of the mooring line behaviour. The final equation is very simple to introduce into a vessel motion program and is also thought to be useful in controller design or stability analysis.     

深海浮式结构物锚泊阻尼参数研究

阐述了锚泊阻尼定义以及当前各种研究方法,选取一组用于实际工程中的锚泊线参数.通过改变预张力、振幅、振荡频率、轴向刚度、法向拖曳力系数和表面流速等参数,研究各参数对锚泊水平阻尼及垂向阻尼的影响.为使研究一般化,文中锚泊阻尼以及预张力等参数采取无量纲形式.     

Measurements of static and dynamic mooring line damping and their importance for floating WEC devices

The dynamic response of the mooring line will be a dominant factor to consider in their use for the station keeping of a wave energy converter (WEC). Due to the relatively small size of WECs and their being moored in relatively shallow waters the effect of waves, tide and current can be of greater significance than for other floating offshore systems. Axial line stretching and high-frequency ‘top-end’ dynamics can importantly modify damping and top-end loading.If a ‘farm’ of devices is to be considered then limitations in sea space may necessitate that the devices be relatively densely packed. This will mean that the ‘footprint’ of the mooring should be constrained, to ensure that the moorings from each device do not interfere and this will have great significance for the loading experienced by the line. One must also consider how the mooring system might change the response of the WEC and so alter its ability to extract power from the waves. Unlike a typical offshore system, the design of moorings for a WEC device must consider reliability and survivability, and the need to ensure efficient energy conversion.The design and operation of a chain mooring for a WEC is considered here. Generic experimental measurements of mooring line damping were conducted in the Heriot-Watt University wave basin at a scale of 1:10. The measurements were conducted on a single mooring line for surge motions and include the study of axial stretching and high top-end dynamics. The laboratory procedures were designed to resemble tests undertaken earlier at ‘full’ scale in 24 m water depth. The measurements were also compared with numerical studies. The experimental findings for WEC devices, supports the conclusion that dynamic mooring line motion will be an important variable, needing to be considered carefully within the design.