倒角化处理对于矩形高层建筑风荷载特性的影响机理研究

通过风洞测压试验，对比不同风向下、不同倒角半径的矩形高层建筑表面风压分布、整体风力及斯托罗哈数St；采用PIV试验，给出建筑的近尾流流动特性，并从流场作用角度，揭示倒角化处理对于矩形高层建筑风荷载特性的影响机理。研究表明:临界风向下，在建筑一侧分离的剪切层发生流动再附，形成分离泡；此时，建筑的阻力达谷值，升力和St达最大值。相比而言，倒角化矩形高层建筑的临界风向小于无气动措施的工况。St主要受到横风向投影宽度和尾流涡对间距的影响，在一定的风向范围内，当倒角半径达一定数值，St将有所增大。在建筑的整体阻力方面，倒角化处理将使得建筑尾流涡对尺寸减小；涡对横向流速增大，涡量掺混运动加剧，旋涡强度减弱。在此作用下，建筑整体阻力降低。在建筑的整体升力方面，采用倒角化处理后，旋涡脱落的不规则性和随机性增大，脱落强度减弱，这促使建筑整体升力减小；但倒角化处理对于升力的减小效应并非见于所有风向。

EFFECT OF ROUNDED CORNERS ON WIND LOAD CHARACTERISTICS OF RECTANGULAR TALL BUILDINGS

Through pressure measurement in a wind tunnel, the wind pressure distribution, total forces and Strouhal numbers of rectangular tall buildings with different corner radius under various wind angles were investigated. The near wake characteristics of the rectangular tall buildings with and without rounded corners were observed by PIV experiment, through which the influence mechanism of rounded corners on the wind load characteristics of the buildings was revealed from the perspective of flow field. Results indicated that under critical wind angle, the separated shear layer reattaches on one side face to form a separation bubble. Therefore, the drag force attains a valley value, and the lift forces and Strouhal number reach peak values. Compared with the building without rounded corner, the critical wind angles of those with rounded corners are smaller. The parameters which control the Strouhal number are the transverse projected width and the distance between vortex pairs in the wake. For the rounded-corner buildings of specific rounded radius, the Strouhal number is increased within some wind angles. The drag force is closely related with vortex pairs in the wake. After adopting the rounded corner, the dimensions of the vortex pairs decrease, while the transverse velocity in the wake increases which implies the intense mixing motion of the fluid and weakened vortex pairs. It gives rise to the decreasing of drag forces. In addition, the irregularity and randomness of vortex shedding are enhanced, while its strength is attenuated by the rounded corner. Then the lift forces are caused to be decreased. However, this decrease tendency is not found for all wind angles.