An experimental investigation of jet flow on a stepped chute

In this paper we report on the results from an experimental study conducted to investigate the properties of the turbulent two-phase flow that occurs on a stepped chute in the jet flow regime. Simultaneous measurements of the void fraction, bubble sizes and bubble velocities were made using a fiber-optic probe. The flow was found to be fully developed by the twelfth step and as expected the head loss along the step was found to be equal to the step height. When the discharge was increased by 40% the average void fraction decreased by 8%, the depth of flow decreases by 9% and the mean velocity increased by 17%. Estimates of the turbulence intensity were computed using the mean and RMS bubble velocities. The turbulence was found to be very intense with values of the turbulence intensity varying from approximately 0.25 to 0.6. A strong negative correlation was observed between the turbulence intensity and the average bubble diameter, i.e., higher turbulence intensities produced smaller bubbles. Hinze's (J. AlChe. 1, 1955, 289) theory was used to show that Reynolds stresses are responsible for the break-up of bubbles and that the magnitudes of the observed values of the turbulence intensity were consistent with the observed bubble sizes.