Research on aerodynamic forces of a cantilevered circular cylinder in a laminar flow and a uniform turbulent flow
-
摘要: 对长径比L/D=2的悬臂圆柱在来流风速5~20m/s(Re=1.73×105~6.90×105)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。Abstract: The flow around a cantilevered circular cylinder with an aspect ratio of 2 in a smooth laminar flow and a uniform turbulent flow (Iu=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 1.73×105 to 6.90×105. 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.
-
Key words:
- cantilevered circular cylinder /
- Reynolds number /
- turbulence intensity /
- aspect ratio
-
表 1 外表面粗糙度对比
Table 1. Comparison of surface roughness
模型表面 热浸镀锌处理 热喷涂处理 Rz/μm 6.155 0~10 40~80 表 2 典型雷诺数下的阻力系数
Table 2. Drag coefficient at typical Reynolds numbers
表 3 脉动风压典型值
Table 3. Typical values of fluctuating wind pressure
Re C′pmax C′pmax出现位置 C′pb 亚临界 2.8×105 0.13 70° 0.10 3.5×105 0.12 70° 0.08 超临界 4.1×105 0.39 110° 0.06 5.2×105 0.24 115° 0.13 6.0×105 0.17 115° 0.14 -
[1] Schewe G. On the force fluctuations acting on a circular cylinder in crossflow from subcritical up to transcritical Reynolds numbers[J]. Journal of Fluid Mechanics, 1983, 133:265-285. doi: 10.1017/S0022112083001913 [2] Zhou B, Wang X K, Gho W M, et al. Force and flow characteristics of a circular cylinder with uniform surface roughness at subcritical Reynolds numbers[J]. Applied Ocean Research, 2015, 49:20-26. doi: 10.1016/j.apor.2014.06.002 [3] Younis N, Ting D S K. The subtle effect of integral scale on the drag of a circular cylinder in turbulent cross flow[J]. Wind and Structures, 2012, 15(6):463-480. doi: 10.12989/was.2012.15.6.463 [4] Sumner D. Flow above the free end of a surface-mounted finite-height circular cylinder:a review[J]. Journal of Fluids and Structures, 2013, 43:41-63. doi: 10.1016/j.jfluidstructs.2013.08.007 [5] 王汉封, 邹超, 王启文, 等.均匀流中悬臂圆柱体气动力雷诺数效应[J].湖南大学学报:自然科学版, 2015, 42(5):65-71. http://d.old.wanfangdata.com.cn/Periodical/hndxxb201505010Wang H F, Zou C, Wang Q W, et al. Reynolds number effects on the aerodynamic forces of a cantilevered circular cylinder in uniform flow[J]. Journal of Hunan University:Natural Sciences, 2015, 42(5):65-71. http://d.old.wanfangdata.com.cn/Periodical/hndxxb201505010 [6] Wang H F, Zhou Y, Mi J. Effects of aspect ratio on the drag of a wall-mounted finite-length cylinder in subcritical and critical regimes[J]. Experiments in Fluids, 2012, 53(2):423-436. doi: 10.1007/s00348-012-1299-z [7] Sumner D, Heseltine J L, Dansereau O J P. Wake structure of a finite circular cylinder of small aspect ratio[J]. Experiments in Fluids, 2004, 37(5):720-730. doi: 10.1007/s00348-004-0862-7 [8] Park C W, Lee S J. Free end effects on the near wake flow structure behind a finite circular cylinder[J]. Journal of Wind Engineering & Industrial Aerodynamics, 2000, 88(2-3):231-246. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=901a69191837ed9426ff013602a9c1c0 [9] Rostamy N, Sumner D, Bergstrom D J, et al. Local flow field of a surface-mounted finite circular cylinder[J]. Journal of Fluids and Structures, 2012, 34:105-122. doi: 10.1016/j.jfluidstructs.2012.04.014 [10] Sumner D, Rostamy N, Bergstrom D J, et al. Influence of aspect ratio on the flow above the free end of a surface-mounted finite cylinder[J]. International Journal of Heat and Fluid Flow, 2015, 56:290-304. doi: 10.1016/j.ijheatfluidflow.2015.08.005 [11] Gu Z F, Sun T F. On interference between two circular cylinders in staggered arrangement at high subcritical Reynolds numbers[J]. Journal of Wind Engineering and Industrial Aerodynamics, 1999, 80(3):287-309. doi: 10.1016/S0167-6105(98)00205-0 [12] Achenbach E. Distribution of local pressure and skin friction around a circular cylinder in cross-flow up to Re=5×106[J]. Journal of Fluid Mechanics, 1968, 34(4):625-639. [13] 顾志福, 孙天风, 贺德馨, 等.高雷诺数时串列双圆柱脉动压力的实验研究[J].空气动力学学报, 1992, 10(2):176-189. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=QK000001972672Gu Z F, Sun T F, He D X, et al. Pressure fluctuations on the surface of two circular cylinders in tandem arrangements at high Reynolds numbers[J]. Acta Aerodynamica Sinica, 1992, 10(2):176-189. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=QK000001972672 [14] Cheung J C K, Melbourne W H. Turbulence effects on some aerodynamic parameters of a circular cylinder at supercritical numbers[J]. Journal of Wind Engineering and Industrial Aerodynamics, 1983, 14(1-3):399-410. doi: 10.1016/0167-6105(83)90041-7 [15] 顾志福, 孙天风, 贺德馨, 等.大湍流度高雷诺数时并列双圆柱的平均和脉动压力分布[J].力学学报, 1992, 24(5):522-528. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=QK000002173081Gu Z F, Sun T F, He D X, et al. Pressure distributions on two circular cylinders of side-by-side arrangements in high-turbulence flow at high Reynolds number[J]. Chinese Journal of Theoretical and Applied Mechanics, 1992, 24(5):522-528. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=QK000002173081 [16] 马文勇, 刘庆宽, 刘小兵, 等.风洞试验中测压管路信号畸变及修正研究[J].实验流体力学, 2013, 27(04):71-77. doi: 10.3969/j.issn.1672-9897.2013.04.013Ma W Y, Liu Q K, Liu X B, et al. Study on correction and distortion effects caused by tubing systems of pressure measurements in wind tunnel[J]. Journal of Experiments in Fluid Mechanics, 2013, 27(04):71-77. doi: 10.3969/j.issn.1672-9897.2013.04.013