B-f jump characteristics in smooth sloping beds

Subject Areas : Subjects

منوچهر شکریان ¹ (دانشگاه شهید چمران اهواز)
محمود شفاعی بجستان ² (دانشگاه شهید چمران اهواز- دانشکده مهندسی علوم آب- گروه سازه های آبی)

Received: 2015-05-07 Accepted : 2019-08-26 Published : 2019-08-23

Keywords: energy dissipation, Hydraulic jump, sloping bed, B-F jump, Stiling basin,

Abstract :

Beacause of the hydraulic jump unstable behavior in adverse-slope stilling basins downstream of sloping beds, the jump toe is transmitted on sloping bed. Therefore, formation of the B-F jump is common in practice. In this research, using dimensional analysis and Incomplete Self-Similarity (ISS) theorem, a general equation was derived to computation of the sequent depth ratio of a B-F jump on smooth sloping bed. The experiments were conducted in a physical model for three different slopes of upstream channel (13.5, 21.5 and 29.5 degree) and downstream stilling basin (-0.05, -0.1 and -0.15 %). The results showed that the sequent depth ratio decreases as the slope of stilling basin increases so that for the stilling basin with the slope of 0.15 % and for the constant position of the jump (E0=0.5), the sequent depth ratio decreases about 60% compared with the slope of 0.05% . Then, the roller length was investigated and based on relative energy loss in the jump a general equation was derived to calculate the roller length of a B-F jump. The results showed that the equation of roller length is independent of upstream channel and stilling basin slopes. Finally, using all of the experimental data the required coefficients were calculated and the mean percentage errors were obtained 8.71 and 13.31 % for the sequent depth and roller lenghth equations respectively

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