峡谷区建坝高度对近坝区风场特性的影响

Study on Influence of Dam Elevation on Wind Field Characteristics Near Dam in Canyon Area

在复杂地形、副热带高压和季风天气等因素共同影响下,高山峡谷区内风场复杂多变,极易形成“狭管效应”,进而导致灾害性大风,对大型工程施工与运行造成较大影响。本文基于流体力学基本原理,采用标准k-ε紊流模型以及PISO(Pressure Implict with Splitting of Operator)算法,以白鹤滩水电站区域发生7级北风为典型计算工况,研究了大坝建坝过程中近坝区风速场变化规律和建坝对风速场的影响范围。成果表明:坝体的阻挡作用使风速场在坝顶处产生绕流分离和风场抬升,在建坝高程以下形成低风速区;建坝高程650 m与750 m时,缆机平台范围内风速约15~16 m/s,大坝下游风速垂直分布显著影响区河道长度分别为4.4H_(t)和4.5H_(t)(H_(t)为建坝高度);坝顶处风速场显著影响高度分别为2.0H_(t)和3.0H_(t)。大坝蓄水至正常蓄水位825 m高度时,大坝下游风场显著影响区河道长度为8.0倍坝高(2.3 km),最大影响河道区长度为30.4倍坝高(8.8 km);坝顶影响高度达到1500 m高度左右,约3.5倍坝高。

Under the common influence of factors including complex terrain,subtropical high pressure,and monsoon weather,the wind field in the alpine canyon areas of is complex and changeable,and it is easy to form the“narrow pipe effect”,which leads to disastrous gales that have a great impact on the construction and operation of large-scale projects.In this paper,based on Fluent,a fluid dynamics computing software,a standard turbulence model and PISO algorithm are used to study the variation of wind velocity field near the dam during dam construction and the influence of dam construction on the wind velocity field,taking the level 7 north wind in Baihetan Hydropower Station as a typical calculation condition.The research results show that the blocking effect of the dam body makes the wind velocity field at the top of the dam generate flow separation and wind field uplift,and a low wind velocity zone forms below the dam elevation.When the dam elevation is 650 m and 750 m,the wind speed within the cable platform is about 15 m/s to 16 m/s,and the channel length of the significant influence area by the wind speed vertical distribution downstream of the dam is 4.4 H_(t) and 4.5 H_(t)(H_(t) being the dam height).The significant influence heights of the wind velocity field at the top of the dam are 2.0 H_(t) and 3.0 H_(t) respectively.When the dam is filled to the normal water level of 825 m,the channel length of the significant influence area by the wind field downstream of the dam is 8.0 times the dam height(2.3 km),and the maximum influence channel length is 30.4 times the dam height(8.8 km).The influence height of the dam top reaches about 1500 m height,which is 3.5 times the dam height.