Analysis of turbulence and tilt by in-situ measurements inside the codend of a shrimp beam trawl
Analysis of turbulence and tilt by in-situ measurements inside the codend of a shrimp beam trawl
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DOI：
10.1016/j.oceaneng.2012.06.014
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发表时间：
2012-10-15
影响因子：
5
通讯作者：
Kim, Yong-Hae
中科院分区：
文献类型：
--
作者：
Kim, Yong-Hae
用Nortek矢量和拖绳张力测量了对虾光束拖网在5次捕捞作业中的尾流和尾部倾角，分析了拖带速度下尾部倾角对尾部湍流强度的影响。尾端后上部的湍流强度在5%~40%之间，并随尾端内平均流速(0.1~0.9m S(-1))的增大而显著降低。同时，利用快速傅立叶变换和Morlet小波方法，确定了拖曳方向或垂直方向的湍流周期较短的时间段在S 2~8之间。在+/-6度范围内，其螺距和横摇也各有不同，其较短的周期主要表现为3个S左右。然而，腔体内的湍流速度与倾角变化和拖绳张力无关，后者随着拖曳速度的增加而显著增加。结果表明，鱼体内的湍动强度和周期性会影响鱼体的运动和主动刺激装置的应用。(C)2012爱思唯尔有限公司。保留所有权利。
The turbulence flow inside the codend and tilt of the codend in a shrimp beam trawl was measured with a Nortek Vector and the towline tension during five fishing operations; data collected for turbulence intensity with codend tilt was analysed under towing speeds. The turbulence intensity at a point in the posterior upper part of the codend ranged from 5 to 40% and decreased significantly by mean flow velocity (0.1-0.9 m s(-1)) inside the codend. Simultaneously, the shorter periods of the turbulence flow in the towing or perpendicular direction were located between 2 and 8 s by the FFT method and the Morlet wavelet method. Pitch and roll of the codend also varied each other within S.D < +/- 6 degrees and their shorter period was shown mostly as 3 s around. However, turbulence flow velocities inside the codend were not related to tilt changes or towline tension, which increased significantly with towing speed. As a result, turbulence intensity and periodicity in the codend could affect the manoeuvring of fish swimming and the application of active stimulating devices. (c) 2012 Elsevier Ltd. All rights reserved.