Management of the Turbulent Boundary Layer using the Strong Spanwise Deformation by a Pair of Streamwise Vortex

本文对湍流边界层与引入主流的一对涡的相互作用过程进行了实验研究。“共流”向下和“共流”向上的两个纵向涡对都是由一个三角翼组 * 8迎角产生的。选择发生器的高度以提供一个涡流，该涡流将由实验参数如：<$MA/U_1 delta_0 <1，<$MA/ utau delta_0 * 1和d_0 / delta_0* 1（<$MA：涡流环量，U_1：自由流速度，delta_0：初始边界层厚度，Utau：摩擦速度，d_0：涡流直径）获得。平均涡量和二次流矢量的等值线显示出一对流向涡，其中心位于30%翼展内的位置，这两种情况下的“共同流”下降和上升。通过对涡的路径和涡量衰减的研究发现，在同向流向上流动的情况下，流向涡衰减较快，流向涡对边界层特性的影响仅限于展向局部区域。然而，在两种情况下的共同流向上和向下，平均速度，湍流强度和雷诺切应力值显着改变附近的涡中心的位置。由于附加应变率的影响，各湍流量等值线在相邻涡之间的某个切片处发生变形。由于二次流的影响，在同向下流时，展向中心位置处的壁面剪应力出现峰值，而在同向上流时，展向中心位置处的壁面剪应力出现最小值。在展向切片中，三维分离线上不存在间断。局部相似性评价与局部尺度不成立，在这两种情况下，共同的流动下降和上升的内层。雷诺法向应力差对流向涡的影响很大。在下一阶段，必须考虑使用一对流向涡的湍流管理。

The interaction process between a turbulent boundary layer and a pair of vortex introduced in the main flow has been examined experimentally. Both longitudinal vortex pair with "common-flow" down and "common-flow" up, were generated by a deltawing set * 8ﾟ angle-of-attack. The generator height was selected to provide a vortex which would be obtained the experimental parameters, such as GAMMA/U_1 delta_0 <1, GAMMA / utau delta_0 * 1 and d_0 / delta_0* 1( GAMMA : vortex circulation, U_1 : free stream velocity, delta_0 : initial boundary layer thickness, Utau : friction velocity, d_0 : vortex diameter). Isovels of mean vorticity and secondary flow vectors revealed a pair of streamwise vortex of which center located at the position inside 30% of wing span for both cases "common-flow" down and up. In case of common-flow up, streamwise vortex reduce faster after the investigation on vortex path and vorticity decay, and the effect of streamwise vortex on the boundary layer characteristics is limited to the spanwise local region. In both cases of common-flow up and down, however, mean velocity, turbulent intensity and Reynolds shear stress values are significantly altered near the location of vortex center. Each isovels of turbulent quantities are deformed at some slice between neighboring vortex due to the effect of the extra rate of strain. Wall shear stress at the spanwise center position' shows peak value in case of common-flow down, conversely minimum one in case of common-flow up due to the secondary flow effect. A discontinuity on three-dimensional separation line is not formed anywhere in spanwise slice. Local similarity evaluated with local scales does not establish in the inner layer in both cases of common-flow down and up. The effect of Reynolds normal stress difference on the streamwise vortex remaining is significantly large. In the next stage, turbulence management using a pair of streamwise vortex must be considered.