撞击流混合器速度信号的混沌识别及标度分析

Analysis of chaos identification and scaling law on velocity signal in ISM

应用三维激光多普勒测速仪,对浸没循环撞击流混合器内的流场瞬时速度时间序列进行获取,并分别按照自相关函数和功率谱分析方法判定了该信号的混沌特性,确定了该信号的频谱变化范围为0—20 Hz;将K41理论引入到撞击流流场分析,验证了Kolmogorov惯性区标度律在撞击流这一特殊流动形式下的普适性原则;按照标度分析的方法计算出了流场不同截面处的β值,发现其撞击区内变化范围在0.8<β<1.6,符合分形流场特征;在撞击区内发现了轴向环形区域的存在,揭示了其存在的物理原理;此外,还发现了流体运动形式不同将会影响到转速对β值的作用效果这一规律;最后,对比了实验结果与K41理论值的差别,分析了出现这一差别的原因。

The instantaneous velocity time series of the flow field in the submerged circulative impinging stream mixer(ISM)was obtained by using the 3D Laser Doppler Anemometry(LDA).The chaos characteristics of the signal were determined by the auto-correlation function and power spectrum analysis method respectively.The spectrum change range of this signal was 0-20 Hz.The K41 theory was introduced into the impinging stream flow field and the results indicated that the Kolmogorov inertial zone scaling law was obeyed in ISM.βvalue at different sections of the flow field was calculated,and the variation range in the impinging zone was found to be 0.8<β<1.6,which was consistent with the fractal flow field characteristics.The existence of an annular area in axial direction of impinging zone was discovered and explained in this paper.In addition,it was also found that the different forms of fluid motion would affect the effect of the rotational speed onβvalue.Finally,the difference between the experimental results and the theoretical value of K41 was compared,and the reason for this difference was analyzed.