Vortex Structures around a Flat Paddle Impeller in a Stirred Vessel

Abstract

Vortex structures and Reynolds stresses around a flat paddle in a mixing vessel have been investigated experimentally by two-component LDV measurement. Phase-averaged mean velocity and Reynolds stresses were obtained to observe the relative relation between the vortical structures and momentum transport. Development of Reynolds shear stress can be recognized along with the separated shear layer released from a flat paddle. Discharge and inflow induced by the roll vortex affect the magnitude of Reynolds shear stress in the separated shear layer. A four-quadrant analysis was applied to find the turbulent motions contributing to the production of the Reynolds shear stress. Most of the Reynolds shear stresses were found to be produced by two turbulent motions, namely, inflow just behind the paddle and large-scale-motion passing from behind the paddle vertically. The two turbulent motions are closely associated with the roll vortex.

Keywords

• mixing vessel
• vortex structure
• reynolds stresses
• roll vortex
• phase averages