Unsteady turbulent fluctuation of abruptly expanding hydraulic jump

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.