Novel Approach to Characterizing the Flow Regime and Fluid Dynamics in a Gas–Solid Fluidized Bed Based on Complex Network Theory

Understanding complex two-phase flow in gas–solid fluidization is crucial to the optimal design, rational scale-up, steady operation, and real-time control of a fluidized bed reactor. In this work, a novel approach based on the complex network theory is developed to characterize the flow regime transition and nonlinear fluid dynamics in a gas–solid fluidized bed. The constructed flow regime complex network (FRCN) consists of 56 nodes, with each featured by 14 quantities that are extracted from the simultaneous time-domain, frequency-domain, and state-space analyses on the in-bed pressure time series. Using the FRCN, various flow regimes in the gas–solid bed are recognized, with an accuracy of 98.2%. Besides, the constructed fluid dynamic complex networks present a scale-free characteristic of a degree distribution. The variation of the scale-free index is consistent with the complexity of the flow dynamics. Thus, it can be used as a descriptor to depict nonlinear fluid dynamics and flow regime evolution in gas–solid fluidization.