Author(s): Chunguang Yuan; Zhang Na
Linked Author(s):
Keywords: Local scour; Pile; Combined waves and current; Silt
Abstract: When a pile is placed in a marine environment, the presence of the pile will cause the flow pattern in its neighborhood to change, resulting in the contraction of flow at sides of the pile and the formation of vortices in its upstreaming and downstreaming. The change of flow will generally lead to an increase in the bed stress and then influence the local sediment transport capacity. It is well known that local scour around the foundations of a hydraulic structure can lead to damage or even to overall failure. In most of previous studies on local scour around pile, scour in steady currents has been investigated quite extensively, and a great many works have been devoted to the flow pattern (horseshoe vortex combined with downflow and contraction of streamlines) and scour equations (e.g., Chiew, 1984; Melville, 1988; Ettema, 1980; Sheppard, 2000; Dey, 1995). For scour around pile under the action of wave alone, the scour depth is found to depend mainly on Keulegan-Carpenter number (KC) and diffraction parameter (D/L). KC number governs the size and life span of horseshoe vortex and lee-wake vortex flow (Sumer et al., 1992; Kobayashi and Oda, 1994); the ratio D/L reflects the wave diffraction process as a incident wave impinging on the pile. For the local scour around a pile under combined waves and current, Sumer (2001) indicated that the scour depth increases with increasing dimensionless parameter Ucw and KC, and attains its steady-current value for Ucw > 0.7.
Year: 2023