微型涡流发生器影响下的湍流边界层流场与摩阻特性

Flowfield and friction characteristics downstream of mirco vortex generator in turbulent boundary layer

在中等雷诺数平板湍流边界层中,利用体视粒子图像测速技术与免标定双层热膜摩阻传感器,测量了单排楔形微型涡流发生器阵列下游的速度场与摩阻,以研究微型涡流发生器对湍流统计量和摩阻特性的影响。速度场测量结果表明:微型涡流发生器诱导下游湍流边界层内产生时均流向涡对和时均流向速度亏损区,导致流向脉动速度的展向预乘能谱出现第二外区峰值。速度场本征正交分解的结果表明:微型涡流发生器诱导产生的流动结构与湍流边界层内的大、超大尺度结构的能量贡献相当,并影响了近壁含能结构的空间分布。摩阻测量实验表明:具有较高高度、展向排列更密集的微型涡流发生器阵列的减摩阻率更高,减摩阻效果可持续至下游80倍自身特征高度处。

The present work uses the stereoscopic particle image velocimetry and calibration-free dual hot-film wall shear stress measurement sensor to measure the flowfield and friction at downstream of the one array of forwards wedge Micro Vortex Generator(MVG)in the turbulent boundary layer at moderate Reynolds number.The result of flowfield measurement shows that MVG produces the streamwise velocity defect regions and streamwise vortices pairs in downstream time-averaged flowfield,which causes the second outer-peak in the spanwise pre-multiplied energy spectra.The result of proper orthogonal decomposition shows that the contribution of energy of structures induced by MVG is equivalent to the that of large-scale structures and very large-scale structures in the smooth-wall turbulent boundary layer,which also significantly affects the spatial distribution of the near-wall structures.The friction measurement experiment shows that MVG array with higher height and closer spanwise arrangement has higher friction drag reduction.The drag reduction effect of MVG lasts downstream to 80 times of its own characteristic height.