Document Type : Original Article
Authors
1
Department of Water structures, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
2
Department of Water structures, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz , Iran.
3
Department of Water structures, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran .
Abstract
Objective: The main goal is to understand better the hydraulic jump mechanism in the sudden expansion channel and investigate the cross-beam system's effect as a roughness for the control and stability of the hydraulic jump.
Method: In this study, the hydraulic jump in a rectangular channel with a sudden diverging section (with a divergence ratio of B=b1/b2=0.67B=b1/b2=0.67) was simulated using a cross-beam system as roughness to control an asymmetric S-type hydraulic jump. This type of jump generates wave impacts that cause flume bed and wall erosion. The simulation was conducted three-dimensionally using the Flow-3D software. The hydraulic jump characteristics were examined by analyzing the velocity at the bed and evaluating three different configurations of the cross-beam system. Variables included the distance of the beam system from the diverging section, the angle of the beams relative to the channel bed, and the number and thickness of the beams at various percentages of the reference tailwater depth.
Results: The results of the numerical simulations, validated by experimental data, demonstrated that using a floor roughness system with cross-beams in various numbers and angles—after optimizing the configuration using velocity coefficient relationships—stabilized and eliminated asymmetric waves and reverse flow in the S-type hydraulic jump across all tested tailwater depths. The cross-beam roughness system also resulted in the highest relative energy loss for configurations 1, 2, and 3, calculated at 36.06%, 74.67%, and 78.6%, respectively, across different sections and tailwater depths. In analyzing the water surface profile for the three cross-beam configurations, configuration 1 (C1) exhibited a more uniform distribution of flow depth in the channel's cross-section, particularly in the sections 0.3 to 2 meters from the end of the structural system. For the total hydraulic head (THH) and the energy dissipation endpoint (or hydraulic jump, j∗Γj∗Γ) in configuration C1, this point was identified after the third beam (N=5). The flow extended with concentrated lines after passing over and under the beams.
Conclusions: Based on the total hydraulic head index and energy dissipation control, configuration C1 demonstrated superior capability in controlling energy dissipation within the structural system before the flow exited the cross-beam roughness system.
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