均匀来流下方柱表面风压非高斯特性的流场机理

Uniform Flow Mechanism of Non-Gaussian Features of Pressure on Square Cylinder

摘要:

极值风压和风压非高斯特性是建筑主体和围护结构抗风设计的重要问题，但其流场机制尚未被澄清。采用大涡模拟方法，在雷诺数Re为22 000的条件下，研究了方柱表面风压非高斯特性随风向角的变化规律，分析了风压非高斯区域与平均流场的关系，基于瞬时流场结构探讨了方柱表面出现极值风压的流场机理。研究表明,方柱表面风压非高斯区域主要分布在方柱后角部位和背风面，而方柱侧面的剪切层再附区域（即分离泡区域）则并未出现明显的风压非高斯现象；方柱后角部位极值风压是由间歇性出现的角部附着涡导致，角部附着涡的形成与方柱尾流中的卡门涡有紧密联系；而方柱背风面极值风压则是由方柱尾流卡门涡的回旋作用引起，极值风压的发生位置会随尾流卡门涡的移动而改变。

Abstract:

The extreme pressures and non-Gaussian feature of pressures are essential problems in the wind resistance design of the main structure and the surrounding structure, but the flow mechanism hasn’t been clarified yet. The non-Gaussian feature of wind pressure under the influence of the wind angle has been investigated using large eddy simulation (LES) at the Reynolds number of 22 000, and the relationship between the non-Gaussian region and the average field are analyzed. Flow mechanisms of extreme wind pressure are discussed based on instantaneous flow structure. The results show that the non-Gaussian region located at the rear corner and leeward side of the square cylinder, and there has not shown non-Gaussian feature at separation bubble region. The intermittent attachment vortex at rear corner creates extreme wind pressures on the surface of the square cylinder, which is closely related to the Karman vortex in the wake of the square cylinder. The extreme wind pressures on the leeward side of the square cylinder are caused by the cyclotron action of the Karman vortex in the wake of the square cylinder, and the positions of extreme wind pressures will change with the movement of Karman vortex.