两类流场下悬臂圆柱气动力特性对比研究

Research on aerodynamic forces of a cantilevered circular cylinder in a laminar flow and a uniform turbulent flow

对长径比L/D=2的悬臂圆柱在来流风速5～20m/s(Re=1.73×10~5～6.90×10~5)下进行层流来流和湍流来流(Iu=9.5%)风洞试验,研究亚临界至超临界雷诺数、高湍流度下悬臂圆柱绕流的气动力特性,包括阻力系数、平均风压分布、脉动风压分布等。结果表明:(1)层流来流下,悬臂圆柱长径比越大,临界区间阻力系数降幅越明显;超临界区间,悬臂圆柱长径比越小,阻力系数越大;亚临界区间脉动风压峰值在距驻点70°位置出现,超临界区间峰值位置后移至110°～115°且脉动风压分布出现明显尖峰。(2)湍流来流下,L/D=2悬臂圆柱脉动风压峰值位置与层流来流超临界雷诺数下的结果一致,峰值大小随雷诺数的变化较为平缓。

The flow around a cantilevered circular cylinder with an aspect ratio of 2 in a smooth laminar flow and a uniform turbulent flow(I u=9.5%)is studied experimentally to investigate the aerodynamic forces,including drag coefficients,mean pressure distributions and fluctuating pressure distributions,in the flow from the subcritical to supercritical regime with a high turbulence intensity.The freestream velocity ranges from 5~20m/s,corresponding to Reynolds numbers in the range of 1.73×10^5 to 6.90×10^5.The results in the smooth laminar flow indicate that:(1)in the critical regime,the step-like drop of the mean drag coefficient grows larger with the increase of aspect ratios;in the supercritical regime,the mean drag coefficient decreases with the increase of aspect ratios;in the subcritical regime,the peak values of the fluctuating pressure locates at the angle of 70°and moves backward to 110°~115°in the supercritical regime.Sharp peaks occur in the fluctuating pressure distributions at supercritical Reynolds numbers.(2)the results in the uniform turbulent flow show that the peak values of fluctuating pressure occur at the same angles as those in the smooth laminar flow at supercritical Reynolds numbers and change little with the change of Reynolds numbers.