Hydrodynamics of Suspensions Agitated by Pitched-Blade Turbine

The complete local fluid velocity vector was determined by three-dimensional phase-Doppler anemometry, while the velocity vector of suspended process particles was being measured. Three-dimensional mean and fluctuating velocities, complete Reynolds stresses, 3-D length macroscales, and turbulent energy dissipation rates are presented. The difference in mean and fluctuating velocities of the process particles and the fluid is also examined. Tangential mean flow opposite to the impeller rotation is observed at certain locations just outside and above the impeller, and impeller fluctuations are found also in the inflow to the impeller. The outflow of the impeller exhibits strong spatial variations. Length macroscales are essentially independent of impeller speed, but vary significantly in the tank. Local energy dissipation rates increase with agitation rate raised to power three. Differences in mean and fluctuating velocities of the two phases are normally small, but increase in the discharge flow, where differences in the direction are also observed.