Author(s): Wang Shuhan; Long Yumei; Si Jinhua
Linked Author(s):
Keywords: Scour hole; Apron length; Plane wall jet; Particle image velocimetry; Turbulent kinetic energy
Abstract: This paper investigated the effects of different apron lengths (L = 0, 5, 10 cm) on the evolution of a local scour hole downstream of a sluice gate with constant discharge (Q = 3.5 l/s) and tailwater depth (H = 14 cm). Owing to the stability of hydraulic structures being threatened by a scour hole caused by a plane-wall jet, it is particularly critical to obtain the potential mechanisms of scour for providing relevant advice. Because of the dramatic sediment-water interaction in the scour hole, most previous studies have only focused on the flow velocity distribution on the apron, while the variation of the flow field inside the scour hole has been neglected (Si et al., 2020). It has been shown that the process of local erosion is influenced by various apron lengths; however, the underlying mechanism has not been well examined (Dey & Sarkar, 2006). In the present experiment, the Particle Image Velocimetry (PIV) technique was used to record the flow field evolution in the local scour hole with different apron lengths, and a camera was used to capture the dynamic profiles of the scour hole during different stages. The results show that the maximum scour depth ds is inversely proportional to the length of the apron L, and the development of maximum scour depth in different lengths of the apron is temporally self-similar. Additionally, the distributions of streamlines, rollers, average kinetic energy (AKE), and turbulent kinetic energy (TKE) were analyzed for three conditions. It is hypothesized that the higher scouring of the short apron may be caused by shear scouring from initial-stage captive rolls that are not fully developed. The significance of TKE in the formation of the scour hole in various apron lengths was demonstrated by gaining the AKE and TKE data from the bottom of the scour hole, thus, the mechanism of the effect on the scour was further explained.
Year: 2024