Turbulence structure and isotropy in stirred vessels

The turbulence structure of the impeller stream of a Rushton turbine was investigated in a vessel of diameter(T) 100 mm using 1 degrees angle-resolved laser-Doppler anemometry (LDA) measurement techniques. The turbine was of diameter D = T/3. Measurements are presented for a region close to the impeller blades for both single and double impeller configurations, Comparisons of the three turbulence levels showed that the turbulence in the impeller stream is mostly anisotropic close to the blades. It is shown that the expressions \u' - v'\/V-tip and \w' - v'\/V-tip call provide a more meaningful and appropriate assessment of the degree of isotropy in the vessel than simple comparisons of the three components of the r.m.s. velocity u', v' and w'.