Abstract: A Particle Dynamics Analyzer (PDA) is employed to measure the velocity and diameter of bubbles (measurement ranges between 0-5 m/s and 0-15 mm), the liquid velocities in liquid circulation zone and in bubble-water plumes are measured in two dimensions by using a Laser Doppler Anemometry (LDA) technique. It is shown that the diameter of bubbles is almost a constant at different levels in the vessel. The radial distribution of velocity of bubbles and liquid in two-phase plumes is found to be well represented ...