Research on fluid motion characteristics and structural evolution in reciprocating mixing tanks

Abstract

A new stirring method, reciprocating stirring, is developed by incorporating a periodic axial reciprocating motion into conventional stirring. This study employs computational fluid dynamics methods, utilizing volume of fluid and user-defined functions to control and analyze the flow field characteristics in a reciprocating stirred tank. Compared to conventional stirring, reciprocating stirring increases the overall fluid velocity by approximately 7.9%, turbulent kinetic energy (TKE) by 35.9% to 45.6%, and the turbulent dissipation rate by 10.6% to 15.7%. The primary reason is the dynamic integration of multiple flow regions, which enhances fluid interface interactions. Additionally, the study investigates the dynamic evolution of the vortex structure, uncovering the correlation between the impeller's start-stop behavior and the vortex area. The optimal impeller plate designs, forward sine-4/12D and reverse sine-5/12D, were determined based on the effective area of TKE. Reciprocating stirring, in comparison to conventional stirring, enhances secondary flow intensity by 67.3% to 93.7% and shortens mixing time by 56.6% to 173.0%.