近坝消能区过水围堰水流特性研究——以富春江水电站船闸改建工程为例

水利枢纽工程改扩建过程中,为协调施工与泄洪的关系,往往采用过水围堰实现枯水期挡水施工、汛期过流泄洪。汛期泄洪时施工围堰的水力指标三维性强、沿程变化较大,处于泄洪建筑物下游消能区内的围堰段受水流冲刷强度较大,而远离消能区的围堰段受冲刷强度相对较小。为寻求安全、经济的围堰防护方式,采用三维数学模型模拟了某枢纽船闸改建工程泄洪时坝下水流流场,重点分析了围堰附近流态、流速分布、涡量分布及压力分布特性。研究结果表明:下泄水流在消能区围堰附近形成水跃,强烈紊动水流顶冲围堰;在横向围堰与上游局部纵向围堰区域形成高流速、高涡量、非静压作用区域,该区域需加强防护。研究成果为该工程围堰分段、分区防护提供了科学依据,也可供类似工程参考。

Research on flow characteristics of overflow in energy dissipation zone near cofferdam: case of ship lock reconstruction project for Fuchunjiang Hydropower Station

For coordinating construction and flood discharge, overflow cofferdam is usually adopted to realize water retaining construction in dry season and flood discharge in flood season when rebuilding or expanding the built hydro-junction. During flood season, the flood discharge hydraulic index of construction cofferdam is three dimensional, and large variation along the river , which scours seriously the cofferdams in energy dissipation zone while attenuates in far away from energy dissipation zone. In order to seek a safe and economical cofferdam protection scheme for a ship lock reconstruction project, a three dimension mathematical model was adopted to simulate the flow field in dam downstream, focusing in the flow pattern, flow velocity distribution, vorticity distribution and pressure distribution near the cofferdam. The simulation results showed that hydraulic jumps formed in the energy dissipation zone near the cofferdam where strong turbulent flow can scour the cofferdam; an area of high flow rate, high vorticity, non-static pressure flow formed at the conjunction part of transverse cofferdam and upstream longitudinal cofferdam, which should be protected. The research results can provide a scientific basis for the protection of the cofferdam in a sectional and partitioned way, which also can be used as reference for similar projects.