旋流静态混合器内脉动壁压符号时间序列复杂度分析

为了研究旋流静态混合器内瞬态壁压非线性符号化特性,利用高速动态数据采集系统对直径为0.1m、长径比为2的旋流静态混合器内湍流脉动壁压进行测量。基于瞬态壁压序列的有限统计复杂性对3种符号化转换方法进行了评估,并优化了数据采样长度和小波分解尺度。分析发现动态法保留静态混合流动有效信息能力优于其他两种方法。运用动态法和db2小波相结合对1～15尺度下的压力波动信号进行多尺度符号化复杂度分析。实验研究表明：随着轴向位置的增加,系统的稳定性增强,相对复杂度降低。7.8125Hz以上信号随着流体微团脉动频率的降低其相对复杂度呈双曲线衰减,而0～7.8125Hz信号相对复杂度随信号频率的降低呈线性衰减,表明静态混合是一种具有宏观大尺度稳定性和局部小尺度不稳定的多尺度结构的流体动力学系统。

Complexity analysis of instantaneous tube-wall pressure fluctuation symbolic series in static mixer with twisted-leaves

The instantaneous turbulent tube-pressure fluctuations in kenics static mixer（KSM） with 0.1m in diameter and 2 in aspect ratio were conducted by high speed dynamic data acquisition system in order to characterize the nonlinear symbolic characteristics.Data sampling length and wavelet decomposed scale are optimized based on finite statistical complexity and the three different methods of symbolization.Dynamic method is better than the other two methods by comparing the adaptability and the ability to retain effective information.Complexities of mutil-scale tube-wall pressure symbolic series were conducted by using the dynamic method and 2rd Daubechies wavelet.The macro stability increases as the axial position increases.The attenuation relationship between pressure fluctuation frequency and relative complexity accords with hyperbolical when the frequency is above 7.8125Hz,but a linear relationship is satisfied when the frequency is below 7.8125Hz.By analyzing different scale signals in a range of 1~15,the multi-scale structures including macro stability and local unstability were reflected in static mixing system.