并列双圆柱尾流切向喷射控制研究

采用PIV实验研究雷诺数为4000、中心距比为1.1的绕并列双圆柱流动施加切向喷射的尾涡控制特性。发现尾涡流场呈现双稳态偏流流型，偏向间隙流的存在将导致圆柱附近时均尾流场沿圆柱中心轴线不对称。分析圆柱尾流涡旋的分布情况和升力频谱，发现可以根据喷射角度θ及射流动量系数C_μ的大小将切向喷射尾流的控制效果分为无效区（θ≤20°或C_μ < 0.135）、非完全控制区（θ > 20°且C_μ > 0.135）和完全控制区（θ > 35°且C_μ > 0.304）。在非完全控制区，切向喷射诱导的射流势流区将并列双圆柱宽尾流抑制为窄尾流，涡系分布范围控制收缩在近尾流的一个三角形区域内。随着喷射角的增大或是射流动量系数的增大，圆柱所受升力的频谱峰值逐渐降低。在完全控制区，并列双圆柱尾流完全被消除，从时均场上看已无明显的涡旋存在，此时控制效果最优。

Control of side-by-side cylinders wake by a pair of tangential jets

The active control of two side-by-side cylinders wake with a Reynolds number of 4000 and a pitch ratio of 1.1 was studied experimentally by the Particle Image Velocimetry (PIV) technique. The flow has a bistable biased flow structure, and the biased gap flow leads to the asymmetry of the flow field. The vortex distribution and the lift spectrum of the cylinders wake were analyzed and it is found that the control effect of tangential jets on the wake can be divided into an invalid zone (θ≤20° or C_μ < 0.135), an incomplete zone (θ > 20° and C_μ > 0.135) and a complete zone (θ > 35° and C_μ > 0.304) according to the values of the jet angle and the jet momentum coefficient. In the incomplete zone, the induced tangential jets potential region can restrain the wake of side-by-side cylinders to a triangle region. The range of the vortex distribution decreases with the increase of the injection angle or the jet momentum coefficient, and the peak value of the lift force spectrum decreases gradually. In the complete zone, the wake of side-by-side cylinders is eliminated and no obvious vortex structure can be found in the time-averaged flow field, and the performance of tangential jets is at its best.