垂直气液两相流混沌吸引子单元面积分析

为了充分反映吸引子结构随时间延迟的变化规律,在现有吸引子形态描述方法基础上定义了吸引子单元面积,通过仿真发现,吸引子单元面积随时间延迟变化曲线第一个波峰的高度和时间延迟主要由信号中大幅值波动的数量、频率决定,利用此规律对实验采集到的气液两相流电导波动信号进行分析,发现在固定液相流量条件下,改变气相流量会导致泡状流、段塞流和混状流中大幅值波动幅度的改变,但相同流型信号中大幅值波动的频率比较接近.将吸引子单元面积随时间延迟变化曲线第一个波峰的时间延迟和落差比作为特征量,可以实现泡状流、段塞流、混状流的流型分类.

Element area analysis of chaotic morphology of verical gas-liquid two-phase flow

In order to better understand the variation of flow structure with delay time, we propose the element area (EA) of attractor morphology parameter in this paper. First, the conductance fluctuating signals and adaptive optimal kernel time-frequency representations of different gas-liquid flows are shown, we can find that flow pattern evolution is always accompanied by the numerical and frequency changes of large amplitude fluctuation (LAF). Then three kinds of signals, i. e., rossler signal, white noise and sinusoidal signal with multi-components, are used for analyzing the simulations, and the results indicate that the greater the frequency of LAF, the smaller the delay time of first crest of EA(τ _peak ) is, and that the more the LAF, the bigger the peak value of first crest of EA(h_peak) is. Additionally, we use the above rule to analyze the conductance fluctuating signals measured from upward gas-liquid two-phase flow experiments and the signal length is selected to be 10 s for analysis. When the water superficial velocity is fixed to be 0.1138 m/s and the gas superficial velocity is gradually increased, we find that the τ _peak is constant and h_peak changes up and down at bubble flow. When the flow pattern evolves into bubble-slug transition flow, the τ _peak begins to turn bigger, and when the flow pattern evolves into slug flow, the τ _peak becomes constant again while the h_peak increases monotonically with the gas flow rate increasing. The τ _peak begins to become smaller as the flow pattern evolves from slug flow into churn flow, and we can find that the τ _peak and h_peak of transition flow are alike. The τ _peak and h_peak of bubble flow and churn flow are also alike because their dynamical mechanisms are similar but the downward trend of bubble flow is more gently than that of churn flow. When the water superficial velocity is fixed to be 0.2719 m/s, we can find similar variations of τ _peak and h_peak to the above. Finally we determine the fall ratio (R_f) which is the ratio of the difference between the first crest and the first trough of EA and the h_peak, and then quantitatively distinguish three typical flow patterns, i.e., bubble flow, slug flow and churn flow by the R_f -τ _peak distribution.