Evaluation of hydraulic jump characteristics induced by reverse stepped weirs with obstacles

ABSTRACT

The hydraulic jump's properties are fundamental to the structural and hydraulic design of structures associated with a stepped weir. The goal of the current research is to analyze features of hydraulic jumps resulting from use of obstacles on a reverse stepped weir (RSW). The physical model was made of wood: 0.5 m height, 1 m length, 0.8 m width. The 18 tests were conducted by using a flat stepped weir (FSW) and a RSW, with and without two obstacles, two positions for obstacles, and three values of flowrates. The results revealed that the RSW with middle obstacles reduced hydraulic jump length by 69% in comparison with FSW models obstacles. For RSW, the length of the hydraulic jump was reduced by 59 and 42% when using middle and end obstacles, respectively, compared to no obstacles. The Fr (4–5.2) indicated the hydraulic jump between the oscillating and steady-jump. Two empirical relationships were proposed to compute relative length and upstream depth of the hydraulic jump and relative to the sequent depth ratio of dimensionless parameters. It concluded that using RSW with obstacles reduces the length of the hydraulic jump and thus reduces the length of the stilling basin, i.e., reduces economic costs.