Determination of 3-D flow fields in agitated vessels by laser-Doppler velocimetry: Use and interpretation of RMS velocities

Laser Doppler velocimetry measurements have been used to calculate the hydraulic and energetic efficiency and turbulence structure for three agitators, a Rushton turbine and two axial agitators: a Mixer TT and a Lightnin A310. The Mixel TT had the highest efficiencies, while ik a viscous liquid (1% CMC solution) all three had comparably low efficiencies. Energy Was dissipated mainly in the stream flowing out of the impeller region and in the main circulation loop. The turbulence length scale was estimated to be of the order of D/5 for the turbulent flow regime and of D/20 for the transitional flow regime. The mean and rms velocities were used to calculate the switching probability, used to simulate stochastically the flow in agitated vessels.