过江通道围堰绕流场流速分布特性与紊流宽度影响研究

Research on the velocity distribution characteristics and turbulent width influence of the flow field around the cofferdam of the cross river channel

施工期围堰绕流场分布特性是船舶通航安全评估需要考虑的主要问题。选址确定后,围堰绕流场分布特性与来流速度和围堰形状密切相关,研究来流速度和围堰形状对围堰绕流场分布特性的影响对围堰设计与船舶安全通航具有重要意义。文章建立了围堰绕流数值计算模型,采用物理模型试验验证了数值计算方法和网格尺寸的合理性和准确性,针对围堰绕流问题及其对船舶通航安全的影响,分析了围堰形状和来流速度对围堰绕流场流线分布、纵向与横向流速分布特性的影响规律,得到了矩形、哑铃形和圆端形三种围堰形状的导流能力以及施工期桥区船舶安全通航所需的通航净宽。研究结果表明:矩形围堰紊流宽度最大,哑铃形围堰次之,圆端形围堰最小,紊流宽度随来流流速的增大而增大。通航侧碍航紊流宽度介于1.3 D~2.1D。

Velocity distribution of the flow field around the cofferdam during construction period is a primary issue to be concerned in safety evaluation for ship navigation.Provided that the construction site was determined,velocity distribution of the flow field around the cofferdam is dictated by the inflow velocity and the shape of the cofferdam to a large extent.An insight into the effects of the inflow velocity and the shape of the cofferdam on the velocity distribution of the flow field around the cofferdam is of great significance for the design of the cofferdam and the safety of ship navigation.The numerical model of the flow field around the cofferdam was established.The validation and the accuracy of the numerical method and the effectiveness of the mesh size were verified by experimental results of the physical model.Effects of shapes of the cofferdam and the inflow velocities on the distribution of the longitudinal and transverse flow velocities of the flow field around the cofferdam were discussed.The flow conductivity of three cofferdam shapes such as the rectangular,the dumb-bell and the round-ended was discussed.The navigable clearance width required for safe navigation of ships during construction period were calculated.Results show that a largest turbulent width is caused by the rectangular cofferdam,followed by the dumb-bell cofferdam and the round-ended cofferdam results in a smallest turbulent width.The turbulent width is increased with the increase of the inflow velocity.The turbulence width obstructing the safety of ship navigation is about 1.3 to 2.1 times the cofferdam width D on the navigable side.