下击暴流作用下超大型冷却塔风场驱动机理与风荷载极值模型  

Wind field driving mechanism and extreme wind load model of a super-large cooling tower under downburst

作　　者：韩光全 柯世堂 杨杰 李文杰 任贺贺 HAN Guangquan;KE Shitang;YANG Jie;LI Wenjie;REN Hehe(Department of Civil and Airport Engineering,College of Civil Aviation,Nanjing University of Aeronautics and Astronautics,Nanjing 211106,China)

机构地区：[1]南京航空航天大学民航学院土木与机场工程系,南京211106

出　　处：《振动与冲击》2022年第22期23-32,共10页Journal of Vibration and Shock

基　　金：国家自然科学基金(51878351,51761165022)。

摘　　要：风荷载是超大型冷却塔结构设计的控制荷载,现行规范风压分布模型均针对良态风气候,缺乏下击暴流等特异风作用下的风场作用机理与风荷载分布模型。首先,采用冲击射流模型和大涡模拟(large eddy simulation,LES)技术模拟下击暴流三维非定常风场,分析了涡环运动、风速变化等风场特性;然后,以内蒙金山电厂228m世界最高冷却塔为例,揭示了处于风场不同径向位置处超大型冷却塔流场特性、风压系数瞬态分布,以及升/阻力系数分布特征;最后,与规范良态风作用下的考虑极值风效应的包络风压进行对比分析。研究表明:下击暴流发生过程中会产生一系列径向移动、反向旋转的气流涡环,各径向位置处风速随之呈现波动变化趋势;涡环撞击塔筒在迎风区外表面和背风区内表面形成高压区,在塔筒内部和背风面尾流区形成漩涡;塔筒内、外表面时程风压系数脉动趋势明显,底部区域受涡环影响震荡显著;冷却塔升力系数基本为0,层平均阻力系数自塔顶沿塔高方向逐渐增大,在塔底达到最大值;涡环对冷却塔的冲击作用极有可能引起瞬时极值风荷载超出规范良态风限值,进而易引起结构的破坏。Wind load is the control load for the structural design of super-large cooling towers. Existing standard wind load distribution models all focus on normal wind climate. However, it lacks models of wind field action mechanism and wind load distribution under specific wind effects like downburst. Firstly, the three-dimensional unsteady wind field of downburst was simulated by the impact jet model and large eddy simulation(LES) technology, and the wind field characteristics of vortex ring movement and the wind speed changes were analyzed. Then, the world-highest cooling tower(228 m) in the Jinshan Power Plant in Inner Mongolia was chosen for the case study. The flow field characteristics and transient distribution of wind pressure coefficient at different radial position of the tower in a wind field as well as the time-history distribution characteristics of mean lift/drag coefficient were revealed. Finally, the extreme wind effect was considered under the normal wind. The simulation results and the wind pressure of specification envelope were comparatively analyzed. The results demonstrate that a series of vortex rings which move radially and rotate reversely are produced during the initiation of downburst. The wind speed at different radial position fluctuates continuously. A high-pressure area is formed on the external windward surface and internal leeward surface when vortex rings impact onto the tower body. Meanwhile, vortexes are formed inside the tower and in the wake zone of leeward surface. The time-history wind pressure coefficients on internal and external surfaces show evident pulsation trend. Besides, there’s a significant oscillation at the bottom zone, which is related to the influences of vortex rings. The lift coefficient of the cooling tower is basically 0. The mean drag coefficient of the layer gradually increases from the top of the tower along the height of the tower, and reaches the maximum value at the bottom of the tower. The impact of the vortex rings on the cooling tower is very likely to

关 键 词：下击暴流 超大型冷却塔 绕流特性 风压分布 升/阻力系数 极值风荷载 

分 类 号：TU332[建筑科学—结构工程]