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

一对流向涡与展向扰动管理湍流边界层的空间变化

基本信息

批准号：
12650171
负责人：
OSAKA Hideo
金额：
$ 2.18万
依托单位：
Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

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.

对展向扰动下流向涡对与湍流边界层的相互作用过程进行了实验研究。实验中采用弦长50mm、翼展40mm、攻角8 °的三角翼在自由流中产生流向涡。三角翼的展向振动频率为0.5Hz和1Hz，振幅为10mm，在流向涡对上增加了展向扰动。传统的时间平均值和合奏平均值是通过热线测量的脉动速度场的流向范围的70倍的初始边界厚度在开始位置的边界层和流向涡之间的相互作用。总结性的意见归纳在以下两个部分，如时间和合奏平均和生产过程。[Time局部表面摩擦系数沿展向随平均速度分布而变化，并增强动量输运。展向扰动在一定程度上忽略了表面摩擦系数的展向变化。而动量输运的展向积分表明，展向扰动对跨边界层的动量输运没有实质性的贡献。平均速度场的展向变化和扰动幅值的展向变化决定了流向脉动分量的系综平均值。任何常规平均都可以分为系综平均和随机分量。对数低剖面可以通过流向范围观察到。[生产过程]研究了时间、系综和随机分量的动能收支。随机分量的动能是由绕流向涡涡核的展向振荡产生的。从整个展向范围内的生产条件考察，目前的管理措施没有出现减阻现象。