Abstract: Net is an important part of cage. In order to solve the problem of numerical research on the movement deformation and stress of net, this paper proposes a mesh group improved method based on Morison equation and lumped mass method. The improved method keeps the volume and quality of the net unchanged before and after the mesh group, and the hydrodynamic force of the improved net is the same as that before the mesh group by adjusting the hydrodynamic coefficient. Through the numerical simulation of the circular net, and compared with the relevant research, the volume loss rate and horizontal drag force of the circular net are analyzed. The results show that: in the flow field of uniform velocity, the horizontal drag force of circular net increases with the increase of velocity, and then reaches the steady state, and the value is basically unchanged; increasing the bottom counterweight of net can effectively reduce the deformation of net, but with the increase of counterweight, the deformation inhibition effect is gradually decreasing. The improved mesh group method is accurate and effective, and has significant simplification effect and a good reference value for improving the hydrodynamic simulation efficiency and calculation accuracy of cage.

Key words: mesh group, circular net, numerical model, water flow, volume loss rate

摘要： 网衣是网箱的重要组成部分。为解决对网衣的运动变形以及受力进行数值研究的问题，基于Morison方程和集中质量法，提出了网目群化改进方法。改进方法保持了网目群化前后网衣的体积和质量不变，并通过调整水动力系数达到改进后的网衣所受水动力与未群化前相同。通过对圆形网衣进行数值模拟，并与相关研究进行对比，分析了圆形网衣的容积损失率和水平拖曳力。结果显示：圆形网衣在均匀流速的流场中，其水平拖曳力随着流速的增大，增加的速率也随之增大，随后达到稳态，数值基本不变；增加网衣底部配重可以有效减小网衣的变形，但是随着配重的增加，其变形抑制效果在逐渐降低。改进的网目群化方法准确有效、简化效果显著，对于提高网箱水动力学模拟效率和计算精度都具有十分较好的参考价值。

关键词: 网目群化, 圆形网衣, 数值模型, 纯水流, 容积损失率