【作者】 孙建军；

【导师】 王元战；

【作者基本信息】 天津大学 ， 港口、海岸及近海工程， 2010， 硕士

【摘要】 抛石基床是重力式码头和直立式防波堤的基础。近年来,作业船舶的大型化和高速化发展,使得螺旋桨的推力以及尾流流速也越来越大。大型船舶尾流流速超过了10-100kg块石的起动流速,导致螺旋桨射流冲刷基床而致使码头损坏的情况大量增加。目前,已有不少重力式码头出现抛石基床被大水流冲刷掏空等局部破坏的现象,给码头泊位的使用带来了严重的安全隐患。船舶尾流作用下抛石基床块石稳定性是工程实践提出的课题,其中包含的流固耦合问题研究也具有重要理论意义。本文主要工作包括以下几方面:1.建立了抛石基床块石冲刷模拟二维有限元模型,通过有限元软件ADINA计算分析了水平面上单层块石的起动流速条件,并与现有理论成果作了比对,验证了本文建立的有限元模型的可行性。2.提出了考虑块石之间遮掩状态影响的起动流速修正公式。块石之间不同程度的相互遮掩状态,对块石的起动流速条件有着较大的影响,本文综合考虑这一因素和块石形状的影响,提出了一个起动流速修正公式。3.为了研究码头岸壁建筑物附近的船舶尾流流场分布状态,运用Flow-3D软件建立了螺旋桨流场数值模型。结合重力式码头断面形式和水深条件,不断改变螺旋桨在水中的位置,包括离地面的距离和距岸壁结构的远近。获得了当螺旋桨处于不同位置时尾流流场分布状况,并对各种工况进行了分析,确定了几种比较容易导致抛石基床表层块石起动的工况。4.针对以上几种容易引起块石失稳的工况,将三维流场分布的计算结果简化为二维模型中流速荷载条件,用ADINA进行流固耦合计算。综合分析比较来流和回流作用下块石的起动条件,发现抛石基床表层块石在回流作用下更易起动。并分析了块石遭冲刷的作用机理和起动流速条件,解释了目前抛石基床遭水流冲刷出现的掏空现象。更多还原

【Abstract】 Rubber bed is the foundation of gravity wharf and vertical breakwater. With the large scale development of ships, the ship stern flow has increasing scouring effect on rubble bed. Today, There are many rubbles bed of gravity wharf that have been scoured destructive. Many stones of the rubble bed have been scoured away, and the breakage makes the quay structures getting to be at risk.This paper presents a 2-dimensional simplified model under an ideal aligning condition of the rubble bed, and firstly numerically simulates the scouring problem of rubble bed by means of finite element software. ADINA software is used to process the FSI problem. A 2-dimensional model of a monolayer of stone on the horizontal ground is founded firstly, computing the incipient velocity of a monolayer of stone on the horizontal ground. Then compared the result with the foregone production, validate the simplified model presented in this paper to be feasible.The study discovered that the conditions of cloak between closer stones make the incipient velocity quite different, and present a new empirical formula of incipient velocity.To study the distribution characteristics of ship stern flow near the quay structures, Flow-3D software is used to simulate the screw propeller. By changing different locations in the water, get different distribution characteristics of ship stern flow accordingly. On this condition, confirm several kind of conditions that the stone would be scoured easily.According to the distribution characteristics of ship stern flow, a 2-dimensional numerical model is established to calculate and analysis the incipient velocity of rubble with the effect of the ship stern flow. The scouring mechanism of rubble bed under the influence of the ship stern flow is concluded, and the empirical formula of incipient velocity of the rubble bed is obtained by fitting method, and explaining the phenomenon that stones of the rubble bed have been scoured away.更多还原