Lift enhancement over flexible nonslender delta wings
Lift enhancement over flexible nonslender delta wings
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DOI：
10.2514/1.31308
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发表时间：
2007-12-01
期刊：
影响因子：
2.5
通讯作者：
Gursul, I.
中科院分区：
文献类型：
--
作者：
Taylor, G.;Wang, Z.;Gursul, I.
本文采用多种技术对柔性非细长三角翼的非定常气动力进行了实验研究。随着机翼柔性的增加，出现了剧烈的流体/结构相互作用，并导致过失速区升力的显著增强。最近发现的这一现象似乎是非细长机翼的一个特征。机翼的自激反对称振动促进剪切层的再附着，从而导致升力增强。这些自激振动是没有观察到的半模型。对于所有非细长机翼，结构振动的主频率的Strouhal数都是1的数量级，这也对应于刚性机翼的剪切层不稳定性的频率。速度测量表明，在过失速区，柔性和刚性机翼上的流动之间存在着显著的差异。柔性的作用是促进剪切层在顶点附近或下游的再附着，这取决于入射角。随着机翼柔度的增加，对涡流有很大的影响，这可能导致在再附着区内轴向流的发展。振荡前缘使时均涡量通量增加，导致环流增加。
Unsteady aerodynamics of flexible nonslender delta wings is investigated in an experimental study using various techniques. Dramatic fluid/structure interactions emerge with increasing wing flexibility and result in substantial lift enhancement in the poststall region. This recently discovered phenomenon appears to be a feature of nonslender wings. Self-excited antisymmetric vibrations of the wing promote reattachment of the shear layer, which results in the lift enhancement. These self-excited vibrations are not observed for a half-model. The Strouhal number of the dominant frequency of the structural vibration is on the order of unity for all nonslender wings, which also corresponds to the frequency of the shear-layer instabilities for the rigid wing. Velocity measurements demonstrate the striking difference between the flows over the flexible and rigid wings in the poststall region. The effect of flexibility is to promote the reattachment of the shear layer near or downstream of the apex, depending on the incidence. There are substantial effects on the vortical flow with increasing wing flexibility, which might lead to the axial How developing within the reattached region. The time-averaged vorticity flux increases due to the oscillating leading edge, which leads to increased circulation.