泡状流“失稳”时空隙率波及其非线性讨论

Discussion on void fraction waves and its non-linear characteristics before bubbly flow transiting to other flow regimes

本文根据不同条件下的实验结果对线性空隙率波动理论进行了分析和讨论,指出由于多相流动的复杂性,线性波动理论在描述气液两相流空隙率波动及其不稳定性方面存在着的局限性。通过空隙率波的测量和非线性分析说明,泡状流"失稳"时是一个混沌动力系统。利用Grassberg的计算方法,计算了泡状流失稳前后空隙率波时域信号的关联维数D2和关联熵K2,泡状流失稳时关联维数D2=2.39,关联熵为0.207。采用了Wolf的方法得到了时间序列最大Lyapunov指数,泡状流失稳时得到的最大Lyapunov指数为0.395。

The paper makes some discussion on the linear theory of void fraction wavesbased on many experimental results. The measurement and non-linear analysis of void fraction waves show that the transition process of bubbly flow to other flow regimes is a chaotic process. With the Grassberg method, the correlative dimensionality D_(2) and the correlation entropy K_(2) of void fraction wavesignals are calculated as D_(2)=2.39 and K_(2)=0.207 before bubbly flow evolving to other flow regimes. The maximum Lyapunov exponent of time series of void fraction wavesis obtained with the Wolf method, and it's 0.395.