Submerged wall jets on corrugated beds

Abstract

The present study was performed to investigate the effect of jet Froude number, submergence factor, and boundary roughness on the submerged wall jets. The jet Froude number ranged from 4 to 10, the submergence factor ranged from 0.375 to 3.5, and the relative roughness ranged from 0.25 to 0.50. The results showed that the rough boundary could effectively reduce the hydraulic characteristic parameters. Compared to the smooth bed, the depression in water surface elevation at the beginning of submerged wall jet and the length scales along and vertical the flow direction over the rough bed decreased. The maximum velocity u m of cross-section appeared farther away from the bed, and the decay of it along the distance was faster than that on the smooth bed. The decay of the ratio for the maximum velocity to the nozzle velocity u 1 had two stages along the distance x/L, where L was the longitudinal distance at which u m = 0.5u 1. The first decay stage was like that in a plane wall jet, and the second decay stage was more and more like a free jump with the decrease of Froude number and submergence factor. While the decay of maximum velocity has good similarity using the new length scale L*, where L* was the longitudinal distance at which u m = 0.2u 1. The shear force coefficients for submerged wall jets on corrugated beds were much smaller than those for free jumps on smooth beds, let alone for free jumps on corrugated beds.