Instabilities of the undertow
Instabilities of the undertow
复制标题
逆流的不稳定性
DOI：
10.1017/s0022112098001694
复制
发表时间：
1998
影响因子：
3.7
通讯作者：
R. Dalrymple
中科院分区：
文献类型：
--
作者：
Li Li;R. Dalrymple
如 Matsunaga、Takehara 和 Awaya (1988, 1994) 所示，波浪在海滩破碎并缓慢流向近海时产生的稳定潜流可能会变得不稳定，并产生一系列水下近海迁移涡流，其长度尺度比入射波更短，时间尺度更长。这些漩涡围绕平行于海岸线的水平轴旋转。我们更大规模的实验室实验表明，在水深上方可能存在额外的涡流层，靠近水面的涡流与波浪引起的水粒子轨迹以相同的方向旋转，而位于大约中间深度的涡流则以相反的方向旋转。理论和数值分析表明，这些涡流是由于底流的不稳定性造成的。在离海浪区较远的地方，涡流会衰减，因为底流的速度剖面在深度上呈线性，因此对任何扰动都是中性稳定的。
The steady undertow created by waves breaking at a beach and slowly flowing offshore can become unstable and create a train of submerged offshore migrating vortices with shorter length scales and longer time scales than the incident waves, as shown by Matsunaga, Takehara & Awaya (1988, 1994). These vortices rotate about horizontal axes parallel to the shoreline. Our larger-scale laboratory experiments show that an additional layer of vortices can exist over the water depth, with vortices near the water surface rotating in the same direction as the wave-induced water particle trajectories, while those located at about mid-depth rotate in the opposite direction. A theoretical and numerical analysis shows that these vortices are due to instabilities of the undertow. Far offshore of the surf zone, the vortex trains decay because the velocity profile for the undertow becomes linear over depth, hence neutrally stable to any disturbances.