Energy Losses and Turbulence Characteristics through Hydraulic Structures Using Laser Doppler Velocimetry (LDV)

Abstract

This paper deals with the experimental investigation of energy losses and turbulence characteristics through hydraulic structures in a rectangular channel using Laser Doppler Velocimetry (LDV). Measurements include turbulence intensity components and mean velocity components. Experiments were conducted with different contraction ratios at different expansion angles for different bed slopes. The results show that the rate of variation of the energy loss increases till an expansion angle of about 30°. This rate of increase decreases above this value of expansion angle. The energy loss is quite high at a contraction ratio of 0.7. Also, the results clearly show that gradual expansion decreases the turbulence intensities in the wall and free surface regions compared to sudden expansion. The maximum values of turbulence intensities occur either close to the bed or at the free surface, with minimum values occurring within the core region. The turbulence intensities, however, increase sharply at the free surface due to free surface wave effect, and have the largest value in sudden expansion.