波流作用下网格锚泊的单个重力式网箱缆绳张力

摘要

以中国沿海常用的周长40 m×10 m的HDPE重力式网箱作为研究对象,采用渔具模型试验狄克生准则,选用大比例尺(λ=1/10)和小比例尺(λ′＝ 1/2)设计制作模型网箱.网箱锚泊系统采用的网格形式与实际使用的一致.模型试验于日本东京大学生产技术研究所海洋环境工程实验室风浪流水槽[50 m(L)×10 m(W)×5 m(D)]进行.实验时前端缆绳水平方向与波流夹角为0°,波浪周期1～2.2 s,波高10～30 cm,对流速0 cm、10 cm和15 cm作用下主缆绳、系框绳以及浮框绳的张力特性进行了研究.结果表明:(1)在纯流作用下,前端缆绳张力最大;(2)在纯波作用下,后侧缆绳张力最大,最大张力(Tmax)与波高(H)的关系为:Tmax=C1H+C2(C1、C2为常数);(3)在波流联合作用下,前端缆绳张力最大,缆绳最大张力(Tmax)与波高(H)的关系为:Tmax=C3eC4H(C3、C4为常数);(4)在波流作用时,左右前端缆绳一般会产生差异,最大差值约30%.%The characters of tension in the mooring lines of a single HDPE gravity cylindrical cage were studied by experimental tests.The proto type of cage had a perimeter of 40 m and a height of 10 m.Based on the Dixon rule of gear tests, two scales were chosen for the experimental model, i.e.λ= 1/10 and λ= 1/2.The experiments were carried out in Ocean Engineering Basin of Institute of Industrial Science of the University of Tokyo.The grid mooring system used in the experiments was geometrically similar to the proto type.The horizontal projections of the front mooring lines were in the same direction of current or incident waves.Uniform current was produced in the whole basin at a velocity of 0 cm/s, 10 cm/s and 15 cm/s.Regular waves with a period of the range from 1 s to 2.2 s and a height varying from 10 cm to 30 cm were generated.Tension in the mooring lines wwa measured.The following conclusions were made from the analysis of measured data: (1) Under the actions of current only, the tension in the front mooring lines was greater than that in rear mooring lines.(2) Under the actions of waves only, the tension in the rear mooring lines was greater than that in the front mooring lines.An empirical formula for the maximum tension (Tmax) in the rear mooring lines was deduced.It turned out that the maximum tension was linearly related to the wave height (H), i.e.Tmax=C1H+C2 (C1 and C2 are constants).(3) Under the combining effects of waves and current, the tension of the front anchor line was again greater than that in the rear one.Another empirical formula was deduced.It showed that the maximum tension in the front mooring lines was exponentially increased with the wave height, i.e.Tmax = C3eC4H (C3 and C4 are constants).