Unsteady turbulent fluctuation of abruptly expanding hydraulic jump

• Published in: Journal of hydraulic research Vol. 63; no. 2; pp. 217 - 231
• Main Authors: Zhang, Jingmei, Bai, Ruidi, Gu, Shenglong, Wang, Hang
• Format: Journal Article
• Language: English
• Published: Madrid Taylor & Francis 04.03.2025; Taylor & Francis Ltd
• Subjects: Asymmetric hydraulic jump; expanding hydraulic jump; Flow distribution; Flow pattern; Flow structures; Flow velocity; Free surfaces; free-surface fluctuation; Hydraulic jump; jump toe oscillation; Oscillations; swinging hydraulic jump; T-jump; Tailgates; Tailwater; Three dimensional flow
• ISSN: 0022-1686; 1814-2079
• DOI: 10.1080/00221686.2025.2468945

The unsteady turbulent features of hydraulic jumps in abruptly expanding channels can be substantially different from classical hydraulic jumps yet lack quantitative investigation beyond the time-averaged three-dimensional flow structure. This paper outlines first the formation conditions for various expanding hydraulic jump flow patterns and then focuses on the unsteady turbulent fluctuation characteristics of T-jumps under varying expansion ratios. The lateral flow expansion is associated with variations in free-surface fluctuation amplitudes and frequencies downstream of the expansion throat, as well as in their impact on the jump toe oscillations in the contraction channel. A stable and asymmetric T-jump displays marked flow variation across the mainstream flow, indicating highly three-dimensional flow structures that extend to the tailgates of the expansion basin. Uneven central-lateral tailgate placement causes spanwise oscillations of the mainstream flow primarily, with the oscillation frequency subject to tailwater control, approach flow velocity, and expansion ratios of the channel.