| The current work presents the results of an experimental study on the effects of submergence on the performance of a submerged hydraulic jump with baffle blocks downstream of a sluice gate. A wide range of Froude numbers, submergence factors, and block sizes, locations and arrangements were covered in the experiments. It was observed that, depending on the submergence factor, two different flow regimes could be established; i.e. the deflected surface jet (DSJ) and the reattaching wall jet (RWJ). Empirical equations were presented for the transitional submergence factor between the two regimes. Also, a theoretical equation was derived for the drag force acting on the blocks. To study the flow field, an acoustic Doppler velocimeter was used to measure the three-dimensional instantaneous velocities. The effect of the block size, location and arrangement on bulk energy dissipation was found to be insignificant. However, the block characteristics played an important role in determining the flow regime. As the size of the blocks increases, or they were moved further downstream, or a second row of blocks was added, the establishment of the DSJ flow regime was enhanced. It was observed that the DSJ flow regime is more efficient in dissipating the kinetic energy of the incoming flow. Also, the rate of reduction of the longitudinal velocity was faster in this flow regime. It was found that a larger portion of the flow depth is influenced by the blocks in the DSJ flow regime compared to the RWJ regime and significant mixing was observed between the centerplane and off-centerplane of the former. The turbulence flow field showed that the turbulence characteristics including turbulence intensities, Reynolds stress, turbulence kinetic energy and energy dissipation are influenced by the blocks in both planes of the two flow regimes, but the magnitudes were significantly larger in the off-centerplane of the DSJ regime. The considerable difference between the two planes of the DSJ flow regime creates a significant shear mixing interface, which is, in turn, responsible for enhancing the dissipation of energy and decaying of the velocity. |
