Laboratory investigation of hydraulic jump in divergent-convergent conversions

Abstract

Hydraulic jump is used as a significant energy-dissipater downstream of hydraulic structures, spillways, gates, and chutes. The novelty of this study is the simultaneous use of divergent-convergent basins to investigate the hydraulic jump characteristics. All experiments were conducted in a channel with a length of 11 m, a depth of 0.7 m and a width of 0.48 m. The results obtained from the divergent-convergent basin models have been compared with those of the sudden divergent basin, gradual divergent basin, classical basin and also with previous research. The results indicate that the ratios of depth (y2/y1) and jump length (Lj/y1) in the divergent-convergent basin have decreased by 48.6% and 122.9%, respectively, compared to the classic basin. These values are equal to 33.8% and 46.2% for the sudden divergent basin, respectively, and 31.7% and 69.9%, respectively, for the gradual divergent basin. In comparison with the classical basins, the energy dissipation in the divergent-convergent basin has increased by 26.8%. Finally, by using dimensional analysis and regression method, several equations were developed to predict the ratio of conjugate depths, length and energy dissipation for the divergent-convergent basins. According to this research, it can be concluded that the divergent-convergent basins with smaller dimensions and more energy dissipation have a much better performance than the standard ones.