Author(s): Siow-Yong Lim; Chen Xie
Linked Author(s): Siow-Yong Lim
Keywords: Local scour; Jet-flipping; Apron length; Wall jet; Sediment; Time duration
Abstract: Experiments were carried out to understand the jet-flipping phenomenon in the local scour process by a 2-D submerged wall jet over an apron. Based on web cam recordings of the scouring process over 7 days, it was noted that the equilibrium scour state was not reached because of the intermittent and cyclical jet flipping action from the bed (an attached bed-jet with digging action to form a deep scour hole) to the water surface (surface-jet with sediment re-filling into scour hole) and vice versa. The scour profiles were different during the digging and filling phases, and the maximum scour depth in the former can be as much as 37% more than the latter. The results showed that the duration of each filling phase increases, while the digging time remains relatively unchanged, as the scour progresses. The duration for each filling phase is much longer compared to the digging phase. The loss of sediment materials on the ridge as scouring progresses is the main reason for filling becoming increasing longer. The duration for these two phases was also found to be significantly affected by the apron length.
Year: 2011