Characteristics of the Velocity Distribution in a Hydraulic Jump Stilling Basin with Five Parallel Offset Jets in a Twin-Layer Configuration

Abstract

The flow structure of vertical and horizontal planes in a stilling basin with five parallel offset jets in a twin-layer configuration for four offset ratios (S1/h=1,2,3,4) has been investigated. The velocity distribution was measured, processed, and subsequently used to characterize the flow structure. The flow pattern in the stilling basin exhibits a mixing flow pattern of jets and hydraulic jumps. As the downstream water depth increases in the stilling basin, five different flow patterns appear successively: free jets, hydraulic jumps, submerged jets and hydraulic jumps, mixed submerged jets and critical jumps, and mixed submerged jets and submerged jumps. The results indicate that the velocity distributions in the vertical and horizontal planes of the lower-layer orifices and in the potential core region of the upper-layer orifices are similar to the classical jet; in other regions, the velocity distribution is similar to the hydraulic jump. In addition, the energy dissipation ratio increases with the increasing Froude number, with a value of greater than 70% at F>8.0. The energy dissipation ratio in the stilling basin with five parallel offset jets in a twin-layer configuration is, on average, 5% larger than that of the SBJ basin and 13% larger than that of the classical jump basin.