非定常扰动对涡破裂的影响

The Effects of Unsteady Perturbation on Vortex Breakdown

在旋涡发生器内进行了涡管内的涡破裂研究。试验表明,不论是泡状或是螺旋状破裂,趋近破裂点时流速均趋于零;非定常扰动使涡轴附近的轴向速度增大,从而延缓了涡破裂的发生;在定常流参数、扰动频率和振幅的适当组合下,扰动可促使破裂状态由泡状转变为螺旋状,大大推迟涡破裂的发生。初步的理论分析表明,上述现象可能来源于流动共振。文中最后还给出了水槽中前缘振动襟翼的实验结果。试验表明,襟翼振动可延缓破裂的发生,且存在一个最佳的频率。试验中还发现,大迎角时,若襟翼不振动,可交替地只在一侧产生前缘涡,襟翼振动可消除这一现象。

The effects of unsteady petturbation on vortex breakdownis investigated on the vortex generator.The experiments indicate that, either in case of spiral or bubble breakdown, the velocity approaches to zero as the breakdown point is approached. When the unsteady perturbation is imposed on the flow , the velocities near the vortex axis are increased, and the breakdown is therefore delayed. In certain combinations of steady flow parameters, frequency and amplitude of perturbation , the type of breakdown can be changed from bubble to spiral , and the breakdown is therefore delayed . From an analysis in terms of generalized Lagrange method, it is recognized tentatively that, this phenomena might be due to flow resonance . In the last part of the article , the experimental results of a delta wing with oscillating leading flap is presented.It is showed that the leading edge vortex break down can be delayed by the oscillation of leading edge flaps,and there is an optimum frequency. It is also found that when the angle of attack is 50? the leading edge vortex would be roll up at one side or another alternatively in case without flap oscillation, but it is not while the flaps are oscillated.