沟槽壁湍流多尺度相干结构实验研究

应用热线测速技术,对沟槽壁面平板湍流边界层的减阻机理进行了实验研究.测量了风洞中并排放置的沟槽壁面平板及光滑壁面平板湍流边界层在不同雷诺数下不同法向位置的瞬时流向、法向速度分量的时间序列信号.运用流向速度分量信号的多尺度子波系数辨识壁湍流多尺度相干结构,用条件采样和相位平均技术提取了壁湍流多尺度相干结构喷射和扫掠时流向速度分量、法向速度分量和雷诺应力分量的相位平均波形.分析了沟槽壁面平板及光滑壁面平板湍流边界层中多尺度相干结构的持续时间、条件相位平均波形等特征.对沟槽壁面平板及光滑壁面平板湍流边界层多尺度相干结构的多种统计平均特征进行了比较,从壁湍流多尺度相干结构控制的角度研究了沟槽壁面平板湍流边界层的减阻机理. 

Experimental study on coherent structure passive control and drag reduction in turbulent boundary layer with grooved surface

The measurement technique of constant temperature anemometry was used to study experimentally the mechanism of drag reduction in turbulent boundary layer with riblet surface.Time sequence signals of longitudinal velocity component and normal velocity component across turbulent boundary layer in the wind tunnel over riblet surface and smooth surface have been finely measured by IFA300 constant temperature anemometer with resolution higher than Kolmogorov scale,together with single-hot-wire-sensor probe and double-hot-wire-sensor probe.The ejection and sweep process of coherent structure burst event were identified by wavelet coefficients of longitudinal fluctuating velocity component.Phased-average waveforms of longitudinal and normal fluctuation velocity,as well as Reynolds stress component of coherent structures burst in turbulent boundary layer were extracted by the conditional sampling technique.The statistic characteristics of coherent structure,such as burst period,phased-average waveforms over riblets surface and smooth surface turbulent boundary layer were compared to clarify the effect of drag reduction over V-grooved riblets surface.The mechanism of drag reduction in turbulent boundary layer over V-grooved riblets surface was studied from the view of multi-scale coherent structure passive control.