Author(s): Xikun Wang; Jin-Hua Si; Jieyun Mao
Linked Author(s):
Keywords: Scour hole; Plane jet; Particle image velocimetry; Plunging jet; Oblique jet
Abstract: We have conducted a series of studies to investigate the flow in the scour hole induced by different types of plane jet using particle image velocimetry (PIV), including that by a plunging jet downstream of a weir without an apron (Si et al., 2018) or with an apron (Si et al., 2019), a submerged wall jet (Si et al., 2020), as well as an oblique jet at varying impinging angles (Mao et al., 2023). The scour hole generated by a plunging jet downstream of a weir without an apron is depicted in Fig. 1(a). It is clearly depicted that four types of roller (or recirculating vortex) are involved in scour development and the scour is mainly caused by the major roller, as shown in Fig. 1(b). The average kinetic energy (AKE) distributions reveal that the rollers are maintained by jet impingements on both the concave scoured bed and the water surface. The gap gradually enlarges between jet regions with high transport capability, which adversely affects scour development. The turbulence kinetic energy (TKE) dissipates along the main jet direction. As the scour hole develops, the regions of significant TKE move successively away from the bed with a reduction in scour rate. The plunging jet zone has negative Reynolds shear stress (RSS), and absolute values there are larger than in other zones in the scour hole. Meanwhile, the regions of significant positive RSS change in size and location with scour development. In addition, the cyclical jet-flipping in the scour hole induced by a wall jet is investigated in Si et al. (2021). The transitional vortical structures during jet flipping (both upward and downward) are clearly captured and analyzed. We also successfully reconstructed the global-domain distributions of pressure in the local scour hole by solving the pressure Poisson equations based on the PIV data (Si et al., 2022). More recently, we conducted experiments to analyze the development of the scour hole induced by an oblique jet on erodible sand bed (Mao et al., 2023). Attention is paid to the effects of varying impinging angle from 20° to 80° on the scour hole profiles and flow structure in the scour hole.
Year: 2023