Control of the Streaky Structure in Turbulent Boundary Layer by means of Streamwise Vortex Pair

流向涡对控制湍流边界层条纹结构

基本信息

批准号：
14350093
负责人：
OSAKA Hideo
金额：
$ 4.42万
依托单位：
Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14350093/
关键词：
Turbulent Boundary Layer Streaky Structure Longitudinal Vortex Organized Motion Scaling Law Spatial Averaging

项目摘要

Interaction process between turbulent boundary layer and longitudinal vortex pair was investigated experimentally. Two-types of longitudinal vortex pair, that is, common-flow up and common-flow down, were generated by delta wing located in free stream and introduced into developed turbulent boundary layer. Radius of vortex is comparable with the boundary layer thickness at the start of the interaction. Circulation of the longitudinal vortex is much less than circulation of whole boundary layer, but, of the same order of circulation in the outer layer. In the present study, spanwise oscillation was applied to vortex generator. Amplitude of spanwise oscillation is a half of wing span of the delta wing. Frequencies of sinusoidal oscillation were chosen as 0.5Hz and 1.0Hz.Effect of spanwise oscillation was investigated with behavior of statistical quantities in free stream. Contours of streamwise vorticity becomes to flattened shape by applying spanwise oscillation. Some strong peaks appea … More r in contours of Reynolds stresses. It is expected that Reynolds stresses measured at a given cross-stream position contain apparent components depending on probability distribution of vortex cantor. Circulation generated by the wing was measured by two different ways, that is, integral of longitudinal vorticity and estimation from lift force obtained pressure measurement. The two results prove that spanwise oscillation has no significant effect on the vorticity generating process.In the interaction process, deformation and relaxation of the mean velocity and Reynolds stresses profile were measured in the boundary layer. The longitudinal vortex pair moves away from the wall in faster rate in case of common-flow up. Spanwise spreading rate of two longitudinal vortex path is larger in case of common-flow down. Decay of maximum longitudinal vorticity is slower in case of common-flow down. At symmetrical plane between two vortex, the interaction between longitudinal vortex makes closely distributed mean velocity contour lines and higher skin-friction coefficient in case of common-flow down. Otherwise, in case of common-flow up the interaction makes widely distributed mean velocity contour lines and low skin-friction coefficient. Effect of extra rate of strain involved in momentum integral equation is applied to explain boundary layer behaviors in the two cases.Effect of the extra rate of strain, ∂W/∂z and ∂V/∂y, was examined in the profiles of three turbulent intensity components and Reynolds shear stress profiles. The boundary layer along symmetrical plane is classified into "cross flow" in case of common-flow down and "identifiable streamwise vortices" in case of common-flow up. The extra rates of strain modify magnitude of turbulent intensity and Reynolds shear stress in the inner layer in case of common-flow down. Otherwise, close to the wall in the case of common-flow up, local adverse pressure gradient is deduced from the fact that magnitude of transverse divergence is grater than that of spanwise convergence.Effect of the interaction on the streaky structure was investigated by simultaneous multi point hot-wire measurement and conditional detection technique. The multi point hot-wire sensor has 12 single hot-wire sensors with 2mm spanwise separation that corresponds to 40 times viscous wall length. The Variable Interval Time Averaging method (VITA) was employed as a detection scheme for low speed streaks. Averaged spanwise spacing of the low speed streaks detected by the scheme is about 150 times viscous wall length. In the common-flow down case, the average spacing is larger at wall-ward secondary current and smaller at up-ward secondary current. The comparison shows that the spanwise oscillation makes the effect somewhat weaker. Less

实验研究了湍流边界层和纵向涡流对之间的相互作用过程。纵向涡流对的两种纵向涡流对，即往返和平流向下，是由位于自由流中的三角洲机翼生成的，并引入了发达的湍流边界层。涡旋半径与交互开始时的边界层厚度相当。纵向涡流的循环远小于整个边界层的循环，但外层的循环顺序相同。在本研究中，将跨度振荡应用于涡流发生器。跨度振荡的振幅是三角洲机翼的机翼跨度的一半。选择正弦振荡的频率为0.5Hz和1.0Hz。研究跨度振荡的效果以自由流中的统计数量的行为研究。通过施加跨度振荡，流涡度的轮廓变为扁平的形状。出现了一些强的峰……在雷诺的轮廓中增加了更多的峰。可以预期，根据涡旋第托的概率分布，在给定的横流位置测量的雷诺应力。机翼产生的循环是通过两种不同的方式测量的，即，纵向涡度的积分和从升力力获得的压力测量的估计。这两个结果证明，跨度振荡对涡度产生过程没有显着影响。在相互作用过程中，平均速度的变形和放松在边界层中测量了平均速度和雷诺应激曲线。如果持续流动，纵向涡流对以更快的速度从墙壁上移开。在公共流下降的情况下，两个纵向涡流路径的跨度扩散速率更大。在公共流下降的情况下，最大纵向涡度的衰减较慢。在两个涡流之间的对称平面，纵向涡流之间的相互作用使分布紧密的平均速度轮廓线和较高的皮肤摩擦系数在公共流下降的情况下。其他，如果相互作用逐一，则可以使分布广泛的平均速度轮廓线和低皮肤摩擦系数。在两种情况下，应用了动量积分方程中涉及的额外应变率的影响。如果在公共流量向下，则将对称平面的边界层分为“交叉流”，而在公共流动的情况下，则将其分类为“跨流”。额外的应变速率改变了在公共流下降的情况下，湍流强度和雷诺剪切应力的幅度。否则，在公共流动的情况下，靠近墙壁，局部不利压力梯度是从横向发散幅度所满足的事实中得出的。相互作用通过简单的多点热线测量和条件检测技术研究了相互作用对条纹结构的效果。多点热线传感器具有12个单热传感器，具有2mm跨度分离，对应于40倍粘性壁长。可变间隔时间平均方法（VITA）作为低速条纹的检测方案。该方案检测到的低速条纹的平均跨度间距约为粘性壁长的150倍。在公共流下方的情况下，壁向二级电流处的平均间距较大，而在向上次级电流时的间距更小。比较表明，跨度振荡会使效果较弱。较少的