波浪作用下筏式养殖结构的动力分析

Dynamic Analysis of the Long-line Culture Facility Under Waves

关键词:  筏式养殖  有限元  波浪  数值模拟

Key words:  Lone-line culture  Finite element method  Wave  Numerical simulation

摘要:

针对筏式养殖设施结构的特点，基于有限元商业软件ANSYS对其进行数学建模，通过数值计算，对不同位置浮标与吊笼的位移和最大锚绳力进行分析。数值模拟研究表明，筏式养殖设施整体结构在波浪作用下呈现周期性的运动趋势，但并未发生浮标或吊笼相互缠绕的现象，说明此筏式结构在波浪作用下能够安全使用。不同位置的浮标与吊笼，由于受到锚绳与筏绳相互牵引的作用，其位移随时间变化的趋势有所不同。两侧锚绳受力变化周期与波浪周期基本一致，迎浪侧锚绳受力明显大于背浪侧，锚绳力最大值约为1000 N。研究结果表明，通过对比不同的波浪工况条件，发现各个浮标和吊笼在水平与垂直方向的位移幅度均随着波高的增加而增大，且垂直方向位移幅度大于水平方向。

Abstract:

The long-line culture has been playing a more and more important role in fish industry in both China and the whole world due to the increase in seafood market demands. The long-line culture facility should sustain a high-energy environment with a full range of loading conditions because high speed ocean currents and strong sea storms are frequent events in the open ocean area. Therefore studies on hydrodynamic characteristics of the facility in the waves are necessary. ANSYS is a commercial program for finite element modeling and simulation. Here we used this program to establish a mathematical model for the long-line culture facility, and analyzed the displacements of the buoy and hanging cage and the maximum mooring line forces at different positions. The simulation results showed that the buoys and hanging cages at different positions displayed different patterns of displacements because of the pulling forces of the float ropes and the mooring line. The three buoys had positive horizontal displacements with the maximum value less than 0.6 m. The periodic changes of the mooring line force were consistent with the period of the waves. The mooring line force on the front side was larger than that on the back side, with the maximum value of ~1000 N. We also compared the displacement amplitudes of the buoys and hanging cages under different wave conditions. We found that the displacement amplitudes of the buoys and hanging cages increased along with the wave height in both horizontal and vertical directions; the amplitudes in the vertical direction were larger than that in the horizontal direction. These results suggested that the long-line culture facility in the waves had periodic motion; the buoys and hanging cages did not intertwine with each other, hence the long-line culture facility could be operated safely in the waves.