On the chaotic characteristics and turbulent mixing mechanisms of elliptical unbaffled stirred tanks

Abstract

This study investigates the chaotic characteristics and turbulent mixing mechanisms of an elliptical unbaffled stirred tank. Simulations and experiments demonstrate that the mixing performance of the elliptical unbaffled stirred tank outperforms that of a cylindrical one. The elliptical unbaffled stirred tank suppresses the formation of the center-surface vortex and columnar eddy while inducing numerous multiscale eddies due to the sidewall squeezing effect. Macromixing time decreases by about 10–15 times. Turbulent kinetic energy in the impeller region increases by 2–3 times, and axial flow number rises by 30%. Correlation dimension and largest Lyapunov exponent quantify the degree of chaos, with increases of 4.4% and 14.3%, respectively. A novel chaotic attractor reconstruction based on the variational mode decomposition method reveals that more random velocity fluctuations lead to more complex chaotic attractors, suggesting that smaller-scale eddies dominate and lead to excellent mixing. This study sheds new insights into enhancing global turbulent mixing in reactors.