湍流边界层相干结构剩余脉动雷诺应力项的实验测量

Experimental Measurement of Residual Pulsant Reynolds Stress Term for Coherent Structures in Turbulent Boundary Layer

用IFA300恒温热线风速仪和X形二分量热线探针以采样间隔小于湍流耗散时间尺度的分辨率精细测量了风洞中平板湍流边界层不同法向位置的瞬时流向、法向速度分量的时间序列信号。用条件采样和相位平均技术提取了相干结构猝发过程中相干结构剩余脉动雷诺应力和随机脉动对相干结构贡献的雷诺应力的条件相位平均波形。基于理论上对湍流相干结构动量方程中随机脉动对相干结构贡献的雷诺应力和相干结构剩余脉动雷诺应力项的分析,对两种雷诺应力项进行了对比研究。研究发现,相干结构剩余脉动雷诺应力项在数值上具有和随机脉动对相干结构贡献的雷诺应力相同的数量级,表明在相干结构动力学模型方程中,相干结构剩余脉动雷诺应力项并不像以前估计的那样可以忽略不计。

Time sequence signals of longitudinal and normal velocity components at different vertical locations in turbulent boundary layer over a flat plate in a wind tunnel were finely measured by a IFA-300 model constant temperature anemometry and X type hot-wire probes.The sampling resolution is higher than the dissipative time scale of turbulent flow.The phase-averaged waveforms of residual pulsant Reynolds stress term of coherent structures and Reynolds stress contribution term of random fluctuation during coherent structures burst process were extracted by conditional sampling and phase-average technique.The residual pulsant Reynolds stress term of coherent structures was compared quantitatively with the Reynolds stress contribution term of random fluctuation based on theoretical analysis.It was found that the residual pulsant Reynolds stress term of coherent structures has the same order of magnitude with the Reynolds stress contribution term of random fluctuation and can not be ignored in the dynamic model of coherent structures.This is not as that estimated before.