SK型静态混合器切割区内速度混沌特性

Chaotic characteristics of velocity in cutting region of Kenics static mixer

为揭示SK型静态混合器内非稳态流动特性,利用激光多普勒粒子分析仪对直径为0.04m、长径比为1.25的SK型静态混合器的切割区瞬时流场进行测量。采用功率谱和最大Lyapunov指数识别混合器内瞬时速度时间序列的混沌特性,利用湍流高阶矩参数分析混沌运动的统计特征。实验结果表明:SK型静态混合器切割区速度波动时间序列具有混沌特性;功率谱函数随频率的增加呈幂函数衰减,瞬时速度脉动主要能量集中在31.25Hz以下;湍流高阶矩分布揭示了切割区内的速度脉动存在非线性拟序结构,混沌运动的概率密度函数偏离高斯分布。

In order to evaluate the unsteady flow characteristics of Kenics static mixer with a diameter of 0.04 m and an aspect ratio of 1.25, the time series of instantaneous velocity in the cutting region were measured with Laser Doppler Anemometry. The power spectrum function and Lyapunov exponent were applied to identify the chaotic characteristics of instantaneous velocity time series, respectively. The statistical characteristics of chaos were evaluated by the higher order items of turbulent flow. The experimental results indicate that the velocity fluctuation has chaotic characteristics from the distribution of maximum Lyapunov exponent and power spectrum which shows the power-law attenuation between power amplitude and frequency. The frequency for main energy of fluctuation is below 31.25 Hz. The analysis shows the existence of coherent structure, and the probability density functions of chaos are out of Gauss distribution.