基于PIV技术的平屋盖表面分离泡流动结构研究

该文利用粒子图像测速技术，通过风洞流场显示试验，观察了大跨平屋盖表面的分离泡现象，给出了不同来流工况下多个可视化平面的旋涡流线和涡量场分布。试验结果表明，当风向垂直于平屋盖迎风前缘时，屋盖顶面将出现典型的分离泡现象，涡量场的负向峰值出现在迎风前缘处，屋面风压力随离迎风前缘距离的增加而减小。均匀流场下流动将在迎风边缘产生分离而后再附，再附长度近乎横跨整个屋盖；而湍流场中的小尺度湍流促使分离剪切层较早地再附形成分离泡，且湍流度越大，旋涡再附长度越短。运用FLUENT模拟了平屋盖表面的分离泡，与流动显示试验结果吻合较好。通过多个可视化平面的综合分析得到分离泡的三维形态特征，建立了旋涡的演化、涡核位置与建筑物表面压力分布的内在联系，获得了若干有价值的结论。

3D CHARACTERISTICS OF SEPARATION BUBBLES AROUND FLAT ROOFS BY PIV TECHNIQUE

Flow visualization of separation bubbles around flat roofs was conducted in a wind tunnel through the Particle Image Velocimetry (PIV) technique. The streamlines and vorticity field with multiple visual planes on the roof surface are performed for different flow conditions. The results indicate that the phenomenon of separation bubbles occurs when the flow approaches normal to the roof's leading edge. The location of front windward corresponds to the negative peak vorticity, and the wind pressure generally decreases with the distance from the leading edge. The flow first separates at the leading edge, and then attaches to the roof surface. The reattachment length is almost across the whole roof in a uniform flow field. The shear layer is prompted to reattach earlier by small scale turbulence in the turbulent flow field, and the shorter the reattachment length is, the greater is the turbulence intensity. Compared with the results of the PIV experiment, the reliability and accuracy of Fluent numerical simulation are validated. Three dimensional morphological characteristics are investigated with comprehensive arrangement of the multiple visual planes. The inner link is established for the evolution of vortices, the vortex core position and pressure distribution. Some valuable engineering conclusions are obtained.