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. Measur ements in the high-intensity impeller zone are compared with measureme nts in the bulk zone for four agitation rates. The mean velocity of th e flow was found not to be constant when scaled with V-tip. This is co ntrary to assumptions and measurements reported in the literature. The energy spectra in the impeller zone scale by the energy dissipation l ength 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 ra nge of high wavenumbers of the energy spectra scale wit!? Kolmogorov's scales. The ratios of energy dissipation rate and the ratios of turbu lent kinetic energy in the impeller zone versus the bulk zone, show a linear increase as the agitation rate is increased. This indicates tha t changing the agitation rate affects flow conditions in the impeller zone more than in the bulk zone. (C) 1998 Elsevier Science S.A. All ri ghts reserved.