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An experimental study on CL2 mechanism of Langmuir circulation

Langmuir循环CL2机制的实验研究

基本信息

批准号：
15540424
负责人：
MIZUNO Shinjiro
金额：
$ 2.37万
依托单位：
Hiroshima Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540424/
关键词：
Air-sea interaction Wave-mean current interaction Organized motion Langmuir circulation CL2 Mechanism Wave-induced Reynolds shear stress Wind-driven current Langmuir循環流 CL2機構

项目摘要

Laboratory experiments have been undertaken to understand the wave-current interaction under the wind waves. The primary purpose is to answer the following question. How do swell waves interact with the wind-driven current in a wind tank? The effects of swell (monochromatic mechanical waves) on the subsurface flow were examined to test the validity of the CL2 mechanism proposed by Craik (1977) and Leibovich (1977). In order to explore the response of the wind-driven flow to mechanical-waves, we used two sets of mechanical waves : One is referred to as the wind-following swell (case FS), and the other the wind-opposing swell (case OS). For this purpose, a vertical cross-sectional plane normal to the wind was systematically and in detail measured both vertically and laterally using a two-component LDV in each of the 2 sets of swell cases of FS and OS under the action of a constant wind speed of 7-8 m/s.A strong wave-current interaction was found in a tank flow when the propagation direct … More ion of mechanical-waves (wave frequency = 1Hz, initial wave amplitude H_0 = 2.5 cm) was reversed. First, for case OS the mechanical-waves highly speeded up the primary circulation in the tank but slightly decayed a pair of 2-dimensional (vertical) Langmuir circulation (2D-LC). Second, for case AS they dramatically slowed down the primary circulation, but enhanced the 2D-LC, leading to the generation of vigorous vertical mixing.First, it is found that the response of the vertical circulation to the monochromatic swell wave is consistent with the CL2 mechanism ; that is, the 2D-LC is enhanced by the wind-following swell but attenuated by the wind-opposing swell. In particular, it tamed out that the wind-following swell caused vigorous turbulent mixing in the whole flow, leading to the slowdown of the primary circulation, which appears to be characteristic of the CL2 mechanism.Second, the swell-induced Reynolds shear stress was negative in case FS but became positive in case OS. This fact appears to be closely related to the slowdown in case FS and the speedup in case OS of the primary circulation. That is, we may conclude that the swell-induced Reynolds shear stress plays an important role in the acceleration and deceleration of the primary circulation, when it is positive and negative, respectively. Less

为了了解风浪作用下的波流相互作用，进行了实验室试验。主要目的是回答以下问题。在风槽中，涌浪如何与风驱动的水流相互作用？为了检验Craik（1977）和Leibovich（1977）提出的CL 2机制的有效性，研究了涌浪（单色机械波）对地下流的影响。为了探索风驱动流对机械波的响应，我们使用了两组机械波：一组被称为顺风涌浪（情况FS），另一组被称为逆风涌浪（情况OS）。为此，在7-8 m/s的恒定风速作用下，利用双分量LDV对FS和OS两组涌浪情况下的垂直于风的横截面进行了系统而详细的纵向和横向测量 ...更多信息机械波（波频率= 1Hz，初始波振幅H_0 = 2.5cm）的离子被反转。首先，对于情况OS的机械波大大加快了主循环在坦克，但略有衰减的二维（垂直）朗缪尔环流（2D-LC）对。其次，对于AS情况下，他们显着减慢了初级环流，但增强了2D-LC，导致产生剧烈的垂直mixing.First，它被发现，垂直环流的单色膨胀波的响应是一致的CL 2机制，即，2D-LC是由风的后续膨胀增强，但风反对膨胀衰减。特别是，它驯服了，风后膨胀造成剧烈的湍流混合在整个流动，导致主环流的放缓，这似乎是CL 2机制的特征。海浪-诱导雷诺剪应力在FS情况下为负，而在OS情况下变为正。这一事实似乎与主气流在FS情况下的减速和OS情况下的加速密切相关流通也就是说，我们可以得出这样的结论：当涌浪引起的雷诺剪应力分别为正和负时，它在主环流的加速和减速中起着重要的作用。少