【作者】 祖小勇；

【导师】 胡旭跃；

【作者基本信息】 长沙理工大学 ， 水力学及河流动力学， 2009， 硕士

【摘要】 在一些通航河流上,由于桥墩的存在恶化了通航条件,导致船舶碰撞桥墩事件时有发生。墩柱周围由于水流情况复杂,为航行的不安全区。目前桥墩周围不安全区宽度的界定多数依据桥墩周围水流流态变化,通过有无桥墩水流紊动特性变化来分析不安全区宽度还比较少。开展桥墩周围水流紊动特性和紊流宽度的试验研究,进一步分析桥墩周围水流情况,有利于确定桥墩周围危害行船安全的水流宽度范围,有重要的工程实践意义。采用理论分析和试验研究的方法,就圆端形桥墩周围的水流紊动特性和紊流宽度开展试验研究。在概化水槽试验中,采用ADV流速仪对桥墩周围水流流速进行测量,采用数据处理软件进行数据分析计算,得到圆端形桥墩周围流场及紊动变化情况,给出了圆端形桥墩周围三维的流速矢量图和各断面的二维流速矢量图及不同水深平面二维流速矢量图。桥墩周围垂线上紊流强度最大位置在0～0.2h与0.8h～h两个区间非均匀分布,在0.2h～0.8h间紊流强度大小分布比较均匀。选用0.883h位置紊流强度横向分布情况为研究对象,发现桥墩存在对紊流强度的变化影响存在极值,极值大小和出现位置离桥墩的距离随着流速增大而增大。据极值出现位置离桥墩距离确定紊流宽度,给出了桥墩紊流宽度与弗汝德数的关系。桥墩周围许许多多大小不等涡体相互掺混是桥墩周围紊流形成的根本原因。涡体在靠近槽壁处大量存在和在接近水面处的大量富集是桥墩周围垂线上紊流强度最大点在0-0.2h、0.8h-1h两个区间非均匀分布重要原因。随着断面平均流速增大,涡体密集点外移且流速的脉动更为剧烈,这便是桥墩存在对水流紊流强度影响极值变大且出现位置离桥墩距离更远的主要原因。提出船舶经过通航桥孔时遇到的险流实际上是船行波、水流、桥墩等共同作用的结果。更多还原

【Abstract】 In some rivers for navigation, boats hit the piers event frequently occur because the existence of the pier worsens the condition of the navigation. The area of turbulence eddy around the pier becomes an insecurity area for navigation. Presently, the computation formulas of unsafe areas around pier emphasize particularly on analyzing the change of current . So there is a few studies that analyze the width by the change of the characteristic of turbulence. Therefore, it will have important project practice meaning to carry on experimental study to research the characteristic of turbulence around a pier and turbulent width and analyze the flow condition which is propitious to ascertain the flow width of endangering the safe of a boat around a pier.The method of theoretical analysis and experimental study is used in this article. The characteristic and its width of the turbulence around the round-ended pier have been studied. The speedometer ADV is used to measure the velocity of the flow around the pier in the conceptual flume. The data of the experiment is computed and analyzed by the data processing software, and the flow field around the pier is found. The three-dimensional charts of the velocity vector around the pier, the two-dimensional charts of the velocity vector of cross sections and different vertical sections are drawn. The location of the maximum of the turbulence intensity on the perpendicular line is to present an inhomogeneous distribution from 0 to 0.2h and from 0.8h to 1h but to present a homogeneous distribution relatively from 0.2 to 0.8h. The horizontal distribution of turbulence intensity of 0.883h is chosen to study. the influence to the turbulence intensity of the pier can come to a maximum, and the value of the maximum and the distance from the location where the maximum occurs to the pier both increases along with the increase of the flow velocity is found. Based on the distance, the relation between the width of turbulence with pier and the Froude number has been presented.Many kinds of vortex at different size mixing mutually around each pier is the fundamental reason for the formation of Turbulence. There are a lot of vortex enrich in the surface and wall of flume is important reason for the location of the maximum of the turbulence intensity on the perpendicular line is to present at 0 to 0.2h or from 0.8h to 1h. Intensive point of vortex move out and flow pulse more intensely, which is main reason as the average velocity of the cross-section increases, the existence of pier effects of flow turbulence intensity become larger and appears farther location distant from the pier. Bringing forward the dangerous stream comes into being when the boat and ship comes across navigability bridge opening is the combined action result of wave , streams , pier and so on in fact.更多还原