壁湍流猝发过程中速度分量的相位差对雷诺应力影响的实验研究

Experimental Investigation on the Effect of Phase Difference between Two Velocity Components to Reynolds Stress during Coherent Structure Burst in Wall Turbulence

用IFA300恒温热线风速仪和×形二分量热线探针,以采样间隔小于最小湍流时间尺度的分辨率,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、展向速度分量的时间序列信号。用子波分析辨识壁湍流相干结构猝发事件的能量最大准则,确定壁湍流相干结构猝发事件的时间尺度;用条件相位平均技术提取了相干结构猝发过程中流向、展向脉动速度分量条件相位平均波形,用互相关方法研究了相干结构猝发过程中流向、展向脉动速度分量条件相位平均波形的相位差关系及其对雷诺应力的影响,发现在缓冲层和对数律区,展向脉动速度与流向脉动速度的条件相位平均波形具有不同的相位;当两者相位基本一致时,雷诺应力达到正的最大值,此时湍流相干结构的产生非常活跃;当两者相位差分别集中在90°和270°附近时,雷诺应力的幅值减小并接近于零,此时湍流相干结构的产生和猝发都得到了抑制。

Time sequence signals of longitudinal and transverse velocity components at different vertical locations in turbulent boundary layer above a flat plate in a wind tunnel were finely measured by constant temperature anemometry of model IFA-300 and X type hot-wire probe. The sampling resolution was higher than the minimum time scale of turbulence. The time scale of coherent structure burst is determined by the maximum energy criterion of wavelet analysis, which is used for identifying burst events in wall turbulence. The phase-averaged waveforms of longitudinal and transverse velocity components during coherent structure burst were extracted by conditional sampling and phase-average technique. The phase-difference relationships between longitudinal and transverse velocity phased-averaged waveforms as well as its effect on Reynolds stress during coherent structure burst have been studied using correlation function analysis methods. It is found that the phase difference relationship between longitudinal and transverse velocity phased-averaged waveforms is different in buffer sub-layer and logarithm-law sub-layer. When their phase-difference is close to 0°or 180°, the Reynolds stress amplitude reaches maximum. At the same time, the turbulence production and burst of coherent structure are extremely active. When their phase-difference is close to 90°or 270°, the Reynolds stress is reduced and approaching to zero while the turbulence production and burst of coherent structure are restrained.