Water Distribution in Very High Velocity Water Jets in Air

This technical note presents the results of an experimental study on the distribution of water in very high velocity water jets in air. Three jets with diameters of 2, 2.5, and 3 mm with velocities in the range of 85–155 m/s were studied. These jets were found to have an inner region that contained most of the water with an outer region in which fine mist was carried by the induced air stream. In between, there was a transition region that might be termed the coarse mist region. In this study, the velocity of the air stream in the central and outer regions was measured with a pitot tube. These measurements were found to merge with the laser Doppler anemometer observations made earlier in the inner and central regions. The water concentration on the axis of the jet decreased rapidly with the axial distance, falling to about 2% at a distance equal to 200d, where d is the jet diameter at the nozzle. As the jet travels away from the nozzle, the relative momentum flux carried by the water phase in the jet continuously decreases and, at an axial distance of 1600d, falls to about 25% of its value at the nozzle.