Vortex Structures around a Flat Paddle Impeller in a Stirred Vessel

Abstract

An experimental study of the structure of the roll and trailing vortex formed around the blades of a flat paddle impeller in a stirred vessel has been carried out. Angle-resolved measurements of all three velocity components were performed by synchronizing laser-Doppler velocimetry with a rotary encoder coupled with the impeller shaft. Almost all data was obtained in the θ=0° plane, located halfway between two baffles. This experimental method makes it possible to capture the details of the vortical structure behind the impeller blade. The formation of a roll and trailing vortex is clearly shown in the resultant axial and circumferential mean velocity vectors and contours of mean vorticity. The size, shape and location of the trailing vortex are shown and compared with the results of Rushton turbines.