Scaling of turbulence characteristics in a turbine-agitated tank in relation to agitation rate

The influence of agitation rate on scaling in a turbine-agitated tank is examined using constant temperature anemometry measurements. Measurements in the high-intensity impeller zone are compared with measurements in the bulk zone for four agitation rates. The mean velocity of the flow was found not to be constant when scaled with V-tip. This is contrary to assumptions and measurements reported in the literature. The energy spectra in the impeller zone scale by the energy dissipation length scales and so did also the low wavenumbers of the spectra in the bulk zone. A small region of the energy spectra in the impeller zone are scaled by Kolmogorov's scales. In the bulk zone, the low-energy range of high wavenumbers of the energy spectra scale wit!? Kolmogorov's scales. The ratios of energy dissipation rate and the ratios of turbulent kinetic energy in the impeller zone versus the bulk zone, show a linear increase as the agitation rate is increased. This indicates that changing the agitation rate affects flow conditions in the impeller zone more than in the bulk zone. (C) 1998 Elsevier Science S.A. All rights reserved.