WAVE GROUP FORCING OF LOW FREQUENCY SURF ZONE MOTION
WAVE GROUP FORCING OF LOW FREQUENCY SURF ZONE MOTION
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低频海区运动的波群强迫
DOI：
10.1142/s0578563499000085
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发表时间：
1999
影响因子：
2.4
通讯作者：
R. Dalrymple
中科院分区：
文献类型：
--
作者：
M. Haller;U. Putrevu;J. Oltman;R. Dalrymple
Bowen 和 Holman (1989) 的近岸位涡平衡被扩展为包括波群引起的辐射应力的强迫。模型结果表明，这些辐射应力产生的强迫可以驱动沿岸流的振荡，其空间结构类似于沿岸流的线性剪切不稳定性。此外，当强迫的尺度 (k,σ) 类似于线性最不稳定模式时，强迫响应几乎是共振的。因此，我们认为波群可能提供产生沿岸流剪切不稳定性所必需的初始扰动，并且还充当线性不稳定性完全衰减的海滩上涡旋运动的来源。对来自 SUPERDUCK (1986) 现场实验的数据进行了分析，以确定空间相干波群的存在。分析证实，在这个开阔的海岸上有时存在与观测到的剪切波运动相当的周期和沿岸空间结构的波群。这表明具有启动沿岸流低频振荡所需空间和时间结构的波群可能存在。
The nearshore potential vorticity balance of Bowen and Holman (1989) is expanded to include the forcing from wave group induced radiation stresses. Model results suggest that the forcing from these radiation stresses can drive oscillations in the longshore current that have a spatial structure similar to linear shear instabilities of the longshore current. In addition, the forced response is nearly resonant when the forcing has scales (k,σ) similar to the linearly most unstable mode. Thus, we suggest that wave groups may provide an initial perturbation necessary for the generation of shear instabilities of longshore currents and also act as a source of vortical motions on beaches where linear instabilities are completely damped. Data from the SUPERDUCK (1986) field experiment were analyzed for the presence of spatially coherent wave groups. The analysis confirms that wave groups with periods and longshore spatial structures comparable to the observed shear wave motions were sometimes present on this open coast. This indicates that wave groups with the required spatial and temporal structure to initiate the low frequency oscillations in the longshore current can exist.