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对垂直于来流方向的圆盘进行非定常测力实验,研究上游二维干扰圆杆和圆盘绕流雷诺数(雷诺数范围为0.44×10⁵~2.74×10⁵)对圆盘阻力及其脉动特性的影响.实验结果表明,无论有无上游干扰,圆盘平均阻力系数均不随雷诺数改变.上游干扰圆杆在降低圆盘阻力系数的同时,使圆盘阻力脉动量增大,而且当圆盘绕流雷诺数大于1.84×10⁵时阻力脉动量的增幅将随雷诺数的加大而迅速增加.对圆盘阻力的频谱分析表明,在圆盘上游无干扰时,圆盘绕流形成的螺旋状涡引起的非轴对称波动频率(斯特劳哈尔数为0.135)为阻力脉动的主频.

Unsteady drag measurements for flow over a circular disk

Unsteady drag measurements were conducted in a low speed wind tunnel to investigate the drag of the circular disk which was normal to the flow. The circular disk was interfered by an upstream two-dimensional rod in the horizontal symmetry plane of the disk in the Reynolds number range from 0. 44 × 10 to 2. 74 × 10~5 based on the disk diameter. The results indicate that the mean drag coefficient of the circular disk does not depend on the Reynolds number which was tested in present study, no matter there is an interference rod upstream of the circular disk or not. Meanwhile, the interference rod leads to decrease of the mean drag coefficient and increase of the drag fluctuation of the circular disk. The increment value of the drag fluctuation increases rapidly, when the Reynolds number is beyond 1. 84 × 10~5. By the frequency analysis, the dominate frequency of the disk drag without the interference rod corresponds to the antisymmetric fluctuation frequency induced by the helical vortex structure (the Strouhal number is 0. 135).