外伸肋板对高层建筑流场影响的PIV试验研究

EXPERIMENTAL STUDY ON THE EFFECT OF EXTENSION RIBS ONFLOW FIELD AROUND HIGH-RISE BUILDINGS BY PIV

研究表明:高层建筑表面附属物,如外伸水平和竖向肋板,能大幅降低结构风荷载。然而,此类气动优化措施的作用机理尚不清楚。针对这一问题最有效的方法是对气动优化前后的建筑周围流场进行对比分析以明确优化措施对流场的作用效果。该文通过粒子图像测速(PIV)试验研究了5种不同布置形式的外伸肋板对高层建筑周围流场的影响,通过对比不同类型外伸肋板对平均和脉动流场的影响,分析了外伸肋板的作用效果,揭示了外伸肋板气动优化的工作机理。结果表明:水平连续横板可以明显限制流场的竖向流动,降低剪切层内的湍流强度。相比水平横板,外伸竖板能更明显地修正模型周围的脉动流场。外伸竖板接近建筑角部时可以改变来流的流动分离过程,减小建筑两侧剪切层曲率,明显减弱建筑周围顺风向和横风向湍流强度。水平和竖向外伸肋板使尾涡沿顺风向和横风向尺寸明显增大。以上流场特征的变化直接影响了作用于建筑上的平均和脉动风荷载。

Studies have shown that the facade appurtenances of high-rise buildings,such as horizontal and vertical ribs,can significantly reduce the wind load acting on buildings.However,the working mechanism of these aerodynamic optimization measures remains unaddressed.The most effective method to solve this problem is to compare and analyze the flow field around the building before and after aerodynamic optimization to figure out the effect of optimization measures on the flow field.In this paper,the influence of five different rib’s layouts on the flow field around a high-rise building was investigated through the Particle Image Velocimetry(PIV)test.The effect of extensional ribs with different layout on the average and fluctuating flow field was compared,the wind resistance performance of extension ribs was analyzed,and the aerodynamic optimization mechanism of facade appurtenances was figured out.The results show that the horizontal continuous ribs can obviously restrict the vertical flow and reduce the turbulence intensity inside the shear layer.Compared with horizontal ribs,the vertical ribs can more significantly modify the fluctuating flow field around the model.The vertical ribs near the building corner can change the flow separation at the leading edge,and reduce the curvature of the shear layer.Consequently,the turbulent intensity of the along-wind and crosswind around the building is obviously mitigated.The horizontal and vertical ribs significantly increase the size of the wake vortex in the along-wind and crosswind directions.The changes of the above flow field characteristics directly affect the average and fluctuating wind loads acting on the building.