考虑不同四塔形式特大型冷却塔群风荷载极值分布特征与取值探讨

塔群干扰作用下特大型冷却塔表面风荷载分布非常复杂,尤其是极值模型更加难以预测。首先,以工程中最常见的串列、矩形、菱形、L形和斜L形五种四塔组合形式为例,进行了320种工况的世界最高220m特大型冷却塔群刚体测压风洞试验。然后,分析了特大型冷却塔局部风压和整体力系数的非高斯和非平稳特征,并基于Hermite法和峰值因子法对比探讨了特大型冷却塔的局部风压极值和整体力系数极值的分布规律,着重讨论了特征角度与局部、整体气动力极值之间的映射关系。最后,提出了冷却塔四塔塔群最大负压极值和整体力系数极值的数学计算模型,建议了考虑不同四塔干扰效应的四塔组合特大型冷却塔群一维极值风压系数估算公式,并验证了上述公式的精确度和有效性。主要研究结论表明:矩形、菱形和L形布置下特大型冷却塔最大负压极值均小于-3.40,矩形布置形式下的负压极值最大,菱形布置下出现强吸力现象的可能性较高;可基于特征角度与塔群脉动风荷载之间的线性关系对特大型冷却塔局部风压极值和整体力气动力极值进行有效预测。

Distribution characteristics and value of extreme wind loads of four super-large cooling towers considering different layouts

The distribution of wind loads of super-large cooling tower is very complicated considering interference effect of towers group,especially the extreme value is highly unpredictable.First,according to the world’s highest cooling tower(220 m)which is being built with engineering background,wind tunnel tests with 320 test conditions for rigid body were performed under five typical four-tower arrangements in engineering practice,namely,single row,rectangular,rhombic,L-shaped,and oblique L-shaped.Then,the non-Gaussian and nonstationary features of local wind pressure and integral force coefficient of super-large cooling tower were analyzed.Based on the Hermite method and the peak factor method,the distribution rules of the extreme wind pressure and extreme integral force coefficient were discussed.The mapping relationship between the characteristic angle and the local and global aerodynamic extremum was emphatically discussed.On this basis,the mathematic calculation model of the maximum negative pressure extremum and the integral force coefficient extremum of the fourtower group was proposed.Finally,we proposed a uniform equation for fitting the extreme wind loads under the four-tower arrangements,and the accuracy and reliability of the equation were verified.The results show that the maximum negative pressure extremum is less than-3.40 under rectangular,diamond,and L-shaped arrangement.The maximum negative pressure under the rectangular arrangement is the highest,and the strong suction is more likely achieved under the diamond arrangement.The local wind pressure extremum and the integral aerodynamic extremum of the super-large cooling tower can be effectively predicted based on the linear relationship between the characteristic angle and the pulsating wind load of the tower group.