Full‐scale observations of wave‐induced vortex generation over a rippled bed
Full‐scale observations of wave‐induced vortex generation over a rippled bed
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DOI：
10.1029/2006jc003841
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发表时间：
2007-10
影响因子：
--
通讯作者：
C. S. Nichols;D. L. Foster
中科院分区：
文献类型：
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作者：
C. S. Nichols;D. L. Foster
[1]我们对波纹床面上涡流产生的理解主要是基于小规模的实验室研究。这类研究提供了相当大的洞察力，尽管对该领域的适用性仍然存在疑问。本文介绍了在可移动的沉积物床上对波浪诱导的涡旋产生事件进行全面调查的观测结果。利用可潜粒子图像测速(PIV)系统，在O.H.Hinsdale波研究实验室的现场尺度实验环境中获得了二维时变速度场的观测结果。观测是在波纹高度和波长分别约为0.01m和0.1m的不规则波纹床上进行的。近海定向流在较陡峭的河床坡面上产生的涡流被规则地喷入水柱，并与后向台阶上的振荡流动的概念模型一致。通过观测，可以检查单个涡旋结构的产生和随后的抛射。涡旋结构是用一种对流场的测量来确定的，该测量方法估计了涡旋完全旋转的时间，称为涡流强度。对这些结构的分析表明，波周期无量纲化的涡旋强度与Keulegan-Carpenter相关。这些结果为波纹河床上的流体沉积物相互作用提供了新的见解。
[1] Our understanding of vortex generation over rippled beds is largely based on small-scale laboratory studies. The insight provided by such studies has been considerable, although questions remain regarding the applicability to the field. This paper presents observations from a full-scale investigation of wave-induced vortex generation events over a movable sediment bed. Observations of the two-dimensional time varying velocity field were obtained with a submersible Particle Image Velocimetry (PIV) system in a field-scale, experimental environment at the O. H. Hinsdale Wave Research Laboratory. The observations were obtained over an irregularly rippled bed with ripple height and wavelength of roughly 0.01 m and 0.1 m, respectively. The vortices generated during offshore directed flow over the steeper bed form slope were regularly ejected into the water column and were consistent with conceptual models of the oscillatory flow over a backward facing step. The observations allowed for an examination of the generation and subsequent ejection of individual vortical structures. Vortical structures are identified with a measure of the flow field that estimates the time for a complete revolution of a vortex called swirling strength. An analysis of these structures reveals that the swirling strength nondimensionalized by the wave period is correlated to the Keulegan-Carpenter. These results offer new insight into fluid sediment interaction over rippled beds.