锥形涡诱导下正方形平屋盖风压特性

摘要

To reveal wind pressure spectra and establishes the energy spectrum, vortex movement or the evolution of the relationship between turbulence scales, the wind tunnel experiments were performed which focused on the vortex axis direction and cross wind direction measuring points. Wind pressure distribution and the vortex axis motion characteristics of square flat roof surface were investigated when the flow was not perpendicular to the windward wall with different flow condition(uniform, grid-generated turbulence and the terrain B)and different wind direction(15°, 30° and 45°)through the rigid model wind tunnel pressure tests. Results show that the maximum wind suction appears near the windward point of lower triangular area with three different flow conditions. The peak mean and rms pressure coefficient reach the maximum at 30° wind direction. For the same incoming flow condition,the angle between the vortex axis and the leading edge of the windward direction and the range of reattachment are gradually decreasing as the wind angle increases. The peak value of the wind pressure spectrum near the windward point with the vortex axis direction is proportional to the corresponding roof wind suction. In the high frequency range, the measured wind pressure spectrum response frequency is corresponding to the peak spectral energy, also with the greater the average wind suction. In the low frequency range, the corresponding frequency is corresponding to the spectral energy peak, also with the greater the pulsating wind suction. The correlation between the measuring points in vortex axis direction with uniform flow condition is poor, and cross spectrum is the exponential decay mode with grid-generated turbulence and terrain B flow condition.%为揭示旋涡作用下的脉动风压功率谱特性和确立谱能量与旋涡运动或湍流尺度之间的演变关系,基于大跨屋盖结构风洞测压试验,以涡轴方向测点列和横风向测点列为研究对象,分析了来流非垂直于迎风墙面时3种不同来流工况(均匀流、格栅紊流和B类地貌)和3种不同风向角(15°、30°和45°)下正方形底面的平屋面风压分布和锥形涡涡轴的运动特征.分析结果表明,3种来流工况下屋面最大风吸力、最大脉动值均出现在屋面下三角区的迎风顶点附近.3种风向角下,30°时在迎风顶点附近锥形涡诱导的平均、脉动风压均达到最强.对于同一来流工况下,随着风向角的逐渐增大,涡轴与迎风前缘的夹角和再附作用范围均在逐渐减小.涡轴方向迎风点附近测点风压谱谱峰值与其对应的屋面风吸力成正比例关系:在高频范围内,测点风压谱相应频率对应的谱能量峰值越大,屋盖平均风吸力也越大;在低频范围内,相应频率对应的谱能量峰值越大,其脉动风吸力也越大.均匀流下涡轴方向各测点间的互相关性较弱,格栅紊流和B类地貌下测点间的互谱曲线呈现指数衰减模式.