Analysis of the effect of roughness height and spacing on hydraulic jump characteristics in the stilling basin downstream of an ogee spillway

Subject Areas : Analysis, design and construction of water structures

Mohammad Hossein Ahmadi ¹ , Amir Vakili ² , Roozbeh Aghamajidi ³

1 - Department of Civil Engineering, Beyza Branch, Islamic Azad University, Beyza, Iran.
2 - Department of Civil Engineering, Beyza Branch, Islamic Azad University, Beyza, Iran.
3 - Department of Civil Engineering, Sepidan Branch, Islamic Azad University, Sepidan, Iran.

Received: 2024-10-02 Accepted : 2025-01-08 Published : 2025-02-09

Keywords: Fluent software, Hydraulic jump, Ogee spillway, Roughness, Two-phase model ,

Abstract :

In the present study, the aim is to investigate the effect of roughness and the change in their height and distance on the characteristics of the hydraulic jump in the downstream stilling basin of the ogee spillway. For this purpose, numerical simulation of the flow pattern and analysis of the geometric characteristics of the ogee spillway with the gate were performed using the Fluent software. The simulation method used in this study is the volume of fluid (VOF) method, which is used to model multiphase flows. The results showed that the use of roughness in the channel bottom has a significant effect on reducing the length and secondary depth of the hydraulic jump. In particular, with increasing roughness height, the ratio of secondary depth to primary depth decreases, which is due to the shortening of the hydraulic jump length and the closer proximity of the primary and secondary depths due to the flow encountering the roughness. On the other hand, increasing roughness height leads to greater flow deflection in the channel bottom. Based on the results, the best spacing for the roughness’s is 2 cm between them, which provides optimal performance in terms of reducing the hydraulic jump length and regulating the flow. The results clearly show that changes in the roughness parameters, especially their height and spacing, play an important role in improving the performance of the stilling basin and controlling the hydraulic jump.

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