上仰及小振幅振荡三角翼流动显示研究

Investigation of flow characteristics of delta wings pitching up and pitching oscillation with small amplitude

为验证折合频率与无量纲频率对涡破裂点位置的影响,在北航大水洞用动态机构三角翼分别进行了不同折合频率k(k=α.C/2U∞)的上仰-停止运动及不同无量纲n(n=fC/U∞)的小振幅的俯仰振荡实验。实验结果表明,在不同迎角范围上仰时不同折合频率对涡破裂点位置有很大影响,如在破裂涡迎角范围,破裂点随迎角的变化曲线会出现山峰状;对于在破裂涡区作小振幅振荡的三角翼,无量纲频率n对破裂点位置变化也有很大影响。其中,无量纲频率n在1.0左右时为临界值。

In order to prove the influnce of the reduced frequency and nondimensional frequency to the location of vortex breakdown, flow visualization tests with a dynamic delta wing have been carried out in a water tunnel of BUAA. Movement types of the delta wing include pitching up in different deduced frequency k （ k = ^＊a C/2 U∞ ） and stopping as well as pitching oscillation with small amplitude in different nondimensional frequency n （ n = fC/U ∞ ） at breakdown vortex regime. In the process from pitching up to stopping the range of angle of attack pitching up has a obvious affect on the variation of vortex breakdown position. When the wing is at pitching oscillation with small amplitude in breakdown vortex regime the nondimensional frequency n has an obvious affect on the breakdown position. It has been shown that nondimensional frequency n = 1.0 is critical frequency.