A Comparative CFD Study on Laminar and Turbulent Flow Fields in Dual-Rushton Turbine Stirred Vessels

Abstract

A computational fluid dynamics(CFD) simulation was carried out to study on flow field characteristics in dual-Rusthton turbine stirred vessels in laminar and turbulent regimes. Model validation was conducted using experimental data in the literature. The simulation results show that flow pattern and dimensionless velocity distribution vary with Reynolds number in laminar regime, while these parameters remain almost unchanged for different Reynolds numbers in turbulent regime. For vessels with a certain geometrical configuration, flow pattern, dimensionless velocity distribution and impeller power number depend mainly on Reynolds number, and are little affected by working medium and enlargement scale. By changing impeller spacing and off-bottom clearance of lower impeller, it is obtained the parallel, merging and diverging flow patterns in turbulent regime, and the changing processes of flow patterns in laminar regime for the three configurations. Total power number has the order of parallel>diverging>merging for the three configurations at the same Reynolds number. With increasing of Reynolds number, the power number of merging configuration shows the largest drop, followed by diverging configuration, and the lowest drop for parallel configuration in laminar regime, while power number rises slightly for the three configurations in turbulent regime.

Keywords

• stirred vessel; dual-impeller; numerical simulation; laminar and turbulent flow; flow pattern.