Laminar mixing performances of baffling, shaft eccentricity and unsteady mixing in a cylindrical vessel

The laminar mixing performance in a cylindrical vessel agitated by a plate impeller is investigated. Several mixing enhancement strategies such as baffling, shaft eccentricity and angularly-oscillating impeller (unsteady mixing) are considered. The flow equations are solved numerically via a Lagrangian particle method based on the Moving Particle Semi-implicit (MPS) technique. It is observed that radial mixing is poor in an unbaffled vessel agitated by a concentric impeller undergoing steady rotation. In general, baffling has marginally improved the radial momentum exchange between the near-wall and inner fluid particles. This shortcoming can be alleviated by introducing the shaft eccentricity and the unsteady mixing procedure. In general, the unsteady mixing procedure with the smaller oscillating amplitude outperforms all the mixing enhancement strategies considered in the current study. •Difference in mixing mechanism for various mixing procedures.•Dependence on number of secondary vortices in promoting mixing.•More uniform intensification of radial mixing for unsteady mixing procedure.