Evaluation of local kinetic energy dissipation rate in the impeller stream of a Rushton turbine by time-resolved PIV

The present paper is dedicated to the direct measurement of the dissipation rate of kinetic energy, ε¯, by means of time-resolved 2D-PIV, in the impeller region of a stirred vessel. Experimental estimation of ε¯ is carried out without simplifications, since all spatial gradients of the fluctuating velocity components are directly measured. At each point, measurements have thus been realized in three orthogonal planes. The present results have been compared with previous ones and discussed according to experimental techniques. A special attention is focused on the contribution of measurements in each plane and some new ideas have been suggested for the assessment of ε¯. In addition, in each measurement plane, the time-variation of the instantaneous fluctuating velocity gradients have been also presented, exhibiting periodicity, with large values of instantaneous dissipation rate, linked to the trailing vortex induced by the blade rotation.