Management of Spatial Variation in Turbulent Boundary Layer by a Pair of streamwise Vortices with Spanwise Perturbation

实验研究了具有展向摄动的湍流边界层与一对流向涡的相互作用过程。向流涡由一个弦长50mm、翼展40mm、攻角为8度的三角翼在自由流中产生。恒定频率0.5Hz和1Hz、振幅10mm的三角翼展向振荡增加了向流涡对的展向扰动。在边界层与流向涡相互作用的起始位置，对70倍初始边界层厚度的流向范围进行了脉动速度场的热线测量，得到了常规的时间平均值和集合平均值。结束语分为时间和总体平均、生产过程两部分。局部表面摩擦系数随平均速度分布呈展向变化，并增强动量输运。展向摄动在某种程度上忽略了表面摩擦系数的展向变化。然而，动量输运的跨向积分表明，跨向摄动对边界层动量输运没有实质性的贡献。平均速度场的跨向变化和摄动的跨向幅度决定了水流波动分量的总体平均值的大小。任何传统的平均都可以分为集合平均和随机分量。通过流向范围可以观察到测井低剖面。[生产过程]研究了时间、集合和随机分量下的动能收支。随机分量的动能是由沿流涡的涡核向展向振荡产生的。从整个生产周期的考察来看，目前的管理没有出现减阻现象。

Interaction process between turbulent boundary layer and a pair of streamwise vortices with spanwise perturbation was investigated experimentally. The streamwise vortices were generated by a delta wing that is 50mm in cord length and 40mm in wingspan located in the free stream with 8 degree in angle of attack. Spanwise oscillation of the delta wing with constant frequencies 0.5Hz and 1Hz and 10mm amplitude added spanwise perturbation onto the streamwise vortex pair. Conventional time averages and ensembles averages were obtained by hot-wire measurements of fluctuation velocity field for the streamwise extent of 70 times initial boundary thickness at starting location for interaction between boundary layer and streamwise vortex. Concluding remarks are summarized in the following two pars such as time and ensemble averages and production process.[Time and ensemble averages] Local skin friction coefficient has spanwise variation depending on mean velocity profile and enhance the momentum transport. Spanwise perturbation somewhat leaves off the spanwise variation of the skin friction coefficient. However, spanwise integral of momentum transport shows that the spanwise perturbation has no substantial contribution to momentum transport across the boundary layer. Spanwise variation of mean velocity field and spanwise amplitude of perturbation contribute to magnitude of the ensemble average of streamwise fluctuation component. The any conventional average can be divided into ensemble average and random components. The log low profile can be observed through the streamwise extent.[Production process] Kinetic energy budget was investigated for time, ensemble and random components. Kinetic energy of random component is generated by spanwise oscillation around vortex core of the streamwise vortices. From investigation of production term in whole spanwise extent, there is no drag reduction phenomenon with the present management.