Abstract

Pressure fluctuations are a key issue in hydraulic engineering. However, despite the large number of studies on the topic, their role in spatial hydraulic jumps is not yet fully understood. The results herein shed light on the formation of eddies and the derived pressure fluctuations in stilling basins with different expansion ratios. Laboratory tests are conducted in a horizontal rectangular flume with 0.5 m width and 10 m length. The range of approaching Froude numbers spans from 6.4 to 12.5 and the channel expansion ratios are 0.4, 0.6, 0.8, and 1. The effects of approaching flow conditions and expansion ratios are thoroughly analyzed, focusing on the dimensionless standard deviation of pressure fluctuations and extreme pressure fluctuations. The results reveal that these variables show a clear dependence on the Froude number and the distance to the hydraulic jump toe. The maximum values of extreme pressure fluctuations occur in the range 0.609<X<3.385, where X is dimensionless distance from the toe of the hydraulic jump, which makes it highly advisable to reinforce the bed of stilling basins within this range.

Highlights

  • Hydraulic jumps are a rapidly varied open-channel flow characterized by a sudden transition from supercritical to subcritical flow regime [1]

  • The results indicate that the maximum value of C 0 p in the expansion ratios of 1 and 0.4 decreases when the Froude number increases

  • Some of the most relevant hydrodynamic characteristics of spatial hydraulic jumps in stilling basins with different expansion ratios are presented

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Summary

Introduction

Hydraulic jumps are a rapidly varied open-channel flow characterized by a sudden transition from supercritical to subcritical flow regime [1]. Hydraulic jumps are classified based on the approaching flow Froude number (Fr1 ). The jump toe, where the upstream flow impinges into the downstream region, is a singular locus with discontinuities in velocity and pressure fields [3]. Energy is dissipated due to the generation of large-scale turbulence structures [4], which are associated with non-negligible hydrodynamic pressure fluctuations acting on the stilling basin floor and sidewalls. These pressure fluctuations may cause severe damage by lifting up slabs, eroding materials, and causing cavitation [5]

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