LIQUID DISPERSION MECHANISMS IN AGITATED TANKS: PART I. PITCHED BLADE TURBINE

An oil into water dispersion, created by a pitched blade turbine, was observed using high speed, stereoscopic motion pictures. Two different dispersion mechanisms were responsible for the break-up of the oil drops, even though both mechanisms occurred in the vortex system trailing from the impeller blade tips. The first mechanism could be described as ligament stretching, since large oil drops were stretched by fluid shear to form elongated ligaments, which subsequently ruptured into small drops. The second mechanism was turbulent fragmentation, where large oil drops were shattered into large droplet clouds the instant they entered the trailing vortex system. Observations of the oil drops undergoing ligament stretching also indicated that velocities in the trailing vortex system were proportional to impeller tip speed.