From Patterns to Cocktails: A Novel Visualization Method for Turbulent Flow Fields in Stirred Reactors

Visualizing flow fields in stirred reactors under turbulent conditions remains a long-standing challenge. Inspired by bartenders creating patterns while mixing cocktails, we introduced pearlescent powder to achieve flow field visualization. We captured images of wall flow structures in various reactors and extracted their fractal dimensions. In comparison to the mixing time, this method effectively reflects the degree of chaos and the variability of mixing performance. Additionally, the fractal dimension shows sensitivity greater than that of traditional chaos metrics. By integrating proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) techniques, we clarified the interactions between vortices of different scales within the reactors, confirmed by Hilbert–Huang spectrum analysis. These analyses revealed the underlying mechanisms for reduced mixing performance in triple-shaft stirred reactors, validated through large-eddy simulation (LES) results. Furthermore, this work provides a novel method for rapidly validating computational fluid dynamics (CFD) models through direct observation of wall flow structures.