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

实验研究了湍流边界层与具有展向扰动的一对流向涡之间的相互作用过程。在8度迎角的自由流中，一个绳长50 mm、翼展40 mm的三角翼产生了顺流涡流。三角翼的展向振动频率为0.5赫兹和1赫兹，振幅为10毫米，在流向涡对上增加了展向扰动。对于边界层和流向涡相互作用的初始边界层厚度为70倍的流向范围内的脉动速度场，通过热线测量得到了常规的时间平均值和集合平均值。结束语概括为时间和集合平均以及生产过程两个部分。[时间和集合平均]局部表面摩擦系数随平均速度廓线而变化，增强了动量输送。跨向摄动在一定程度上忽略了侧摩阻力系数的跨向变化。然而，动量输送的展宽积分表明，展向摄动对跨边界层的动量输送没有实质性的贡献。平均速度场和扰动幅值沿展向的变化对流向脉动分量的集合平均值的大小有贡献。任何常规平均值可分为集合平均值和随机分量。[生产过程]对时间组分、系综组分和随机组分的动能收支进行了研究。随机分量的动能是在流向涡的涡核周围沿展向振荡产生的。从整个跨度范围内的生产条件考察，目前的管理不存在减阻现象。

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.