Effects of mooring pattern on dynamic characteristics of a deep-water aquaculture cage
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摘要: 针对一种三角形高密度聚乙烯深水养殖网箱，该研究基于有限元法建立了波浪流作用下网箱动力响应计算模型，并通过开展模型比尺1∶15的水池试验，分析比较了网箱在纯波、波流组合条件下动力响应的计算结果与试验数据，两者相对误差均在10%以内。在此基础上，考虑原型网箱海况数据，设计波流要素值取为：波高 (H) 4~6 m、周期 (T) 9 s、流速 (v) 0.5~1.5 m·s−1，分析了单点系泊和多点系泊方式浮架变形以及网箱系泊力的情况，并进一步分析了系泊方式对网箱运动特性的影响。结果表明，波流作用下，多点系泊布置时的系泊力峰值大于单点系泊情况，且随着流速和波高的增加，两者相差幅度增大；在大浪强流条件(H=6 m，T=9 s，v=1.5 m·s−1)时，多点系泊能够一定程度上降低浮架的变形；两种系泊方式对浮架的升沉影响极小，但多点系泊时浮架在x轴上的位移大于单点系泊时浮架的位移，两者峰值相差25.64%；单个周期内网衣平面轮廓图显示网衣的变形程度几乎一致。Abstract: We established a numerical model for calculating the dynamic characteristics of a triangular high-density polyethylene (HDPE) deep-water aquaculture cage in waves and current based on the finite element method. To verify the accuracy of the numerical model, we carried out a series of physical model tests on the single-point mooring (SPM) cage under the conditions of pure wave and combined wave-current, in which the model scale was set at 1: 15. The relative error between the numerical and experimental results was within 10%. Afterwards, considering the sea state of the prototype cage, the calculated parameters for waves and currents were as follows: wave heights 4–6 m, period 9 s, current velocity 0.5–1.5 m·s−1. We analyzed the deformation of the floating collar and the mooring force of the cage with single-point mooring (SPM) and multiple-point mooring (MPM). Besides, we discussed the effect of the mooring pattern on the motion characteristics of the cage. The results show that under the conditions of wave and current, the peak value of MPM force was higher than SPM force, and the difference became greater with the increase of velocity and wave height. Under the condition of severe waves and strong currents, the MPM system can reduce the deformation of the floating collar. However, the mooring pattern had little influence on the heave of the cage collar. For the MPM system, the x-axis displacement of the collar was greater than that of the SPM system, in which the difference was 25.64%. During a wave period, the xz plane profiles of the net deformation under sea conditions were almost the same for the two different mooring systems.
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图 5 纯波条件下网箱动力响应计算结果与试验值比较
Figure 5. Comparison of dynamic responses between calculated and experimental results of net cage under pure waves
图 6 波流条件下网箱锚绳力比较
Figure 6. Comparison of mooring force for net cage under waves and current
图 7 不同系泊方式的网箱布置图
上部水平线为海平面,下部水平线为海底
Figure 7. Layout of cage with different mooring systems
The upper level is sea level and the lower level is the seabed.
图 8 各工况下不同系泊方式的锚绳力峰值
Figure 8. Peak value of mooring force under different sea conditions
图 9 锚绳力历时曲线 (H=6cm, v=1.0 m·s−1)
Figure 9. Time history of mooring force under wave height of 6 m and current velocity of 1.0 m·s−1
图 11 D处达到应力峰值时浮架的变形情况
Figure 11. Deformation of floating frame when stress peak reached at D
图 15 一个波周期内网衣的xz面轮廓图 (v=1.5 m·s−1，H=6 m，T=9 s)
Figure 15. xz surface contour of net during a wave period (v=1.5 m·s−1, H=6 m, T=9 s)
表 1 网箱主要参数
Table 1. Parameters of net cage
组件
Component参数
Parameter模型值
Model value原型值
Prototype value浮管
Floating pipe浮管直径
Pipe diameter/mm26.67 400 壁厚
Wall thickness/mm1.57 23.5 形状
Shape三角形 三角形 长度
Length/m1.33 20 网衣
Net网目
Mesh size/mm45 45 目脚直径
Twine diameter/mm2 2 网衣高度
Height/m0.4 6 材料
MaterialPE PE 锚绳
Mooring line长度
Length/m4 60 直径
Diameter/mm2.67 40 材料
MaterialPE PE 浮筒
Buoy高度
Height/m0.13 2 直径
Diameter/m0.1 1.5 沉子
Sinker质量
Mass/g20×5.93 20×20000 材料
Material混凝土 混凝土 
下载: 导出CSV
表 2 浮架各点处变形
Table 2. Deformation at different points of floating collar
浮架点编号
Point No.应力 Stress/MPa 单点系泊
SPM多点系泊
MPMA 11.07 11.77 B 3.44 2.93 C 14.99 13.88 D 19.50 18.01 E 2.34 2.68 F 2.11 3.03 G 3.16 2.25 H 7.37 3.71
下载: 导出CSV
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