Comparative study of flow in a mixing vessel stirred by a solid disk and a four bladed impeller

Laminar flow in an unbaffled mixing vessel stirred by a solid disk rotor and a 4-blade impeller was simulated using the CFD software package FLUENT. The computational geometries and grids were generated using a pre-processor software package (Gambit) and then exported to Fluent where the rotating reference frame approach was employed to predict the flow field. The flow field is characterised by two recirculation regions, the centre of which was investigated. The swirl velocity and the Z-vorticity at the recirculation centre are much higher for the 4-blade impeller than for the solid disk rotor. Simulated results also show that both the swirl velocity and the Z-vorticity are higher near the impeller. Results show that at Reynolds number (Re) = 200 the 4-blade impeller exhibits a sharp increase in the swirl velocity near the axis at the bottom of the mixing vessel, which generates an upwards vortical flow. The results show that the solid disk rotor may be viable for smooth laminar applications