两种串列方柱气动性能的试验研究

针对两种布置形式（水平布置和对角布置）的串列双方柱，通过同步测压风洞试验，在雷诺数为Re = 8.0×104、间距比为P/B = 1.75 ~ 5.00（其中P为方柱中心间距、B为方柱边长）条件下，得到了两种布置形式串列双方柱的表面风压，重点研究了对角串列双方柱的气动力、风压分布、Strouhal数等气动性能随方柱间距的变化规律，并与水平串列双方柱进行比较。水平串列双方柱的气动力在P/B = 3.00 ~ 3.50时会发生跳跃现象，下游方柱的平均阻力由负值突变为正值，而对角下游方柱平均阻力系数则均为负值。结果表明：当P/B<3.00时，对角串列双方柱的平均和脉动气动力系数、最大平均负压强度和脉动风压系数均大于水平串列双方柱，而当P/B > 3.00时则情况相反；对角串列双方柱的Strouhal数明显小于相同间距下的水平串列双方柱，且在P/B <3.00时对角串列双方柱的升力功率谱出现了多个峰值。

Experimental Study on Aerodynamic Characteristics of Two Tandem Square Cylinders in Different Arrangements

Wind tunnel tests are conducted to investigate aerodynamic characteristics of two tandem square cylinders in horizontal and diagonal arrangements at a Reynolds number of Re = 8.0×104 and spacing ratios of P/B = 1.75 ~ 5.00, where P is the center-to-center spacing of the two cylinders and B is the width of the square cylinder. The surface pressure distributions on cylinders in two arrangements are obtained. Efforts are mainly devoted to the aerodynamic characteristics of two diagonal tandem cylinders, and the comparison with those of the two horizontal tandem cylinders. The results show that the mean drag coefficients on the downstream cylinder for the horizontal arrangement discontinuously vary from a negative value to a positive one when the spacing ratio increasing from 3.00 to 3.50, while the mean drag coefficients for the diagonal arrangement remain negative in all spacing investigated. For P/B< 3.00, the mean and fluctuating aerodynamic forces, the maximum of mean negative pressures and the fluctuating pressures of two diagonal tandem cylinders are generally larger than those for the horizontal tandem cylinders, whereas the scenarios are completely contrary for P/B > 3.00. Furthermore, the Strouhal numbers of the diagonal cylinders are significantly smaller than those of the horizontal ones at the same spacing. It is interesting to note that there are multiple peaks in the lift power spectra for the diagonal cylinders for P/B < 3.00.