PIV测量非定常自由来流中的三角翼前缘涡

在南航非定常风洞中,运用PIV测量技术,研究了非定常自由来流下三角翼前缘涡瞬时涡结构的变化。通过分析三角翼前缘涡速度矢量、涡量以及流动拓扑结构的变化可知,在减速过程中,破裂的前缘集中涡重新卷起,形成涡量较强的集中涡,横截面流动拓扑结构显示,流动结构从不稳定的焦点变成稳定的极限环,这也就说明前缘集中涡的破裂点位置向下游移动;在加速过程中,集中涡很快破裂,涡量随之减小,流动拓扑结构从稳定的极限环变成不稳定的焦点,前缘集中涡的破裂点位置向上游移动。分析认为外部压力梯度的变化可能是导致涡破裂位置移动的原因。

Vortex structure on a delta wing in unsteady free stream via Particle Image Velocimetry

The instantaneous vortex structure of the leading-edge vortices on a delta wing in unsteady free stream is investigated via particle image velocimetry in unsteady wind tunnel of NUAA.The results show that during the deceleration part of the cycle,the breakdown vortex is rolled up again,the vorticity becomes concentration,the topology changes from an unstable focus to a stable limit cycle and the breakdown position moves downstream.During the acceleration, the vortex break down quickly,the vorticity dispersed,the crossflow topology changes from the stable limit cycle to an unstable focus.This indicate that the breakdown position moves upstream.Through analyzing the adverse pressure gradient plays an important role on the phase delay of the breakdown position.