高雷诺数下覆羽控制直翼型流动分离的位置影响实验

Position-dependence straight-wing experiments of artificial coverts in flow separation control at a high Reynolds number

本文在二维机翼上安装了仿生的覆羽结构,在5.0×105的雷诺数下研究它们控制前缘流动分离的效果.覆羽是指覆盖在鸟类翅膀上的多排短而柔软的带有锯齿状尖端的羽毛.它们覆盖在长而硬的飞羽边缘,使鸟的翅膀保持流线型.当流动分离发生时,这些柔性锯齿形的人工覆羽在来流的激励下能够自适应地变形和颤振.在风洞实验中,本文使用高时间分辨率的粒子图像测速仪(PIV)来测量机翼上表面的速度场,并使用热线风速仪来测量尾流中的高频湍流脉动.安装在20%弦长处的人工覆羽在前缘分离流的激励下会自适应地大幅翻转.安装在80%弦长处的覆羽则会被尾缘卷起的脱落涡向上抬起,并在准平衡状态下轻微摆动.这两类人工覆羽均能够有效地控制流动分离,并减小尾流的湍流脉动强度.

We experimentally investigate the leading-edge flow separation control effect of the bio-inspired coverts installed on a straight wing model at the chord Reynolds number of 5.0×105.By covert,we indicate the multiple rows of short and flexible contour feathers with serrated tips overlaying on the bird’s wings.They cover the edges of the remiges(long and stiff flight feathers)and keep the bird’s wings in a streamlined shape.When flow separation occurs,these artificial,flexible,and serrated coverts flap and flutter adaptively,driven by the ambient airflow,like the real feathers on the upper surface of a bird’s wing.In the wind tunnel tests,we used time-resolved particle image velocimetry(PIV)to measure the velocity vector fields on the upper surface of the wing,and hot-wire anemometer to measure the turbulent velocity fluctuations in the wake flow.When installed at 20%of the chord length,the coverts flap adaptively driven by the separated flow.When at 80%,on the other hand,the coverts are lifted upwards by the revised flow near the trailing edge and slightly flutter at a quasi-equilibrium state.Both cases show effective flow separation control results with smaller wake areas and attenuated fluctuation intensities.