Abstract
The construction of stilling basin with adverse slope change the characteristics of hydraulic jump such as sequent depth ratio, length of jump ratio, length of roller and energy dissipation ratio, consequently the dimensions of stilling basin are changed, also using baffle blocks with different configurations develop these characteristics. In this study different shapes of baffle block (models (A), (B), (C) and (D)) installed in the stilling basins at adverse slopes (- 0.03, - 0.045, - 0.06) in addition to horizontal bed, all these models are tested in the stilling basin to show their effects on the characteristics of hydraulic jump, the experiments applied for the range of Froude number (Fr1) between 3.99 and 7.48. The baffle block model (D) showed good results when compared with models (B) and (C), therefore it used with arrangement of (single and double row) and compared with baffle block model (A) at slopes (0, - 0.03, - 0.045, - 0.06) to study the effects of baffle blocks on hydraulic jump when bed slopes are changed. In general using baffle block caused a reduction in sequent depth ratio, length of jump ratio and the length of the roller, but the energy dissipation ratio increased.
Highlights
The hydraulic jump is a phenomenon that occurs when a super critical flow is changed to subcritical flow when the flow obstructed
The characteristics of hydraulic jump affected when the bed conditions of stilling basin are changed, these bed conditions represented by using adverse slope of stilling basin and availability of appurtenances as baffle block
Hydraulic jump at the adverse bed slope represent an unstable phenomenon which generates some difficulty in the controlling of it, previous studies showed that the hydraulic jump at adverse slopes greater than (- 0.025) is impossible to control, and other studies showed an impossible to keep the jump completely on the adverse slope [4], [5]
Summary
The hydraulic jump is a phenomenon that occurs when a super critical flow is changed to subcritical flow when the flow obstructed. The characteristics of hydraulic jump affected when the bed conditions of stilling basin are changed, these bed conditions represented by using adverse slope of stilling basin and availability of appurtenances as baffle block. The friction in the bed of stilling basin would be responsible for the stability of jump on an adverse slope at a minimum value of upstream Froude number (Fr1), the presence of artificial roughness, baffle blocks or sills are essential to reach to stable condition [7]. Baffle blocks one of these devices which used to stabilize the jump and dissipate energy as a result of impact action [10]. At adverse bed of stilling basin the specific energy in up stream of hydraulic jump (E1) and in the end of the hydraulic jump (E2) can compute by equations (2) and (3) respectively [3]. The losses in energy due to hydraulic jump compute by the equation:
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