Evaluating the Hydraulic Performance of USBR II Stilling Basin with Rough Bed

Abstract

Stilling basins are built in conjunction with dams, weirs, and gates to dissipate the high kinetic energy of incoming flow and prevent severe scouring of the downstream riverbed. Dissipation of this high energy can be achieved through forming a hydraulic jump. The hydraulic jump features, including the relative length, ratio of sequent depth, and energy dissipation, are utilized as criteria to evaluate the efficiency of the stilling basin operation. The present study involved conducting experimental and numerical tests to evaluate the performance of the USBR II stilling basin downstream of an ogee spillway using six upstream Froude numbers ranging between 6.37 and 14.97. Experiments were conducted for the Typified USBR II stilling basin. The results were used to perform mesh sensitivity for numerical simulation. The USBRII stilling basin with different rough beds was numerically simulated using FLOW-3D software. The rough beds were designed using three roughness intensities, 10%, 15%, and 22%, and three relative roughness heights: 1, 0.75. and 1. According to the numerical results, distributing staggered cubic elements in the bed of the USBR II stilling basin at 10% intensity and a relative roughness height of (1) enhanced the stilling basin performance compared to the smooth bed and other rough beds. In the case of the best roughness bed, the sequent depth ratio decreased by about 12.1%, and the energy dissipation enhanced by around 5.1% compared to the Typified basin.

Keywords

• Hydraulic jump
• Numerical simulation
• Relative energy dissipation
• Roughness
• Sequent depth ratio
• Stilling basin