金枪鱼延绳钓捕捞作业状态的数值模拟

一种基于有限元原理的非线性混合法被用于预测捕捞作业中的金枪鱼延绳钓的形状与张力，为渔具设计提供理论方法，并以期在设计阶段能替代传统的水槽模型试验，为实际渔业生产作业调整提供有益的技术参数。构成延绳钓渔具的绳索可以被一系列绝对柔软的被称为绳索要素的单元所模拟，因此，整个延绳钓渔具可以被看作为一系列绳索要素在其两端点通过无摩擦铰接连接而成的集合体。根据最小位能原理，可以导出描述系统平衡状态的非线性基本平衡方程式。利用Newton-Raphson方法，通过一系列的负荷-形状迭代法求解基本平衡方程式，可以获得海流作用下延绳钓渔具作业时的形状和张力分布的数值解。简化模型的回流水槽试验验证表明，本方法具有较好的计算精度和解的收束性与稳定性。

A numerical model for predicting the fishing operation status of tuna longlines

In this paper, ropes are modeled as an infinitely flexible, straight rope element, and then the whole longline is able to be regarded as an assembling of the rope elements connecting each other at their ends by a frictionless hinge. A group of nonlinear basic simultaneous equations describing the equilibrium state of longlines are deduced, based on a finite element formulation. Newton-Raphson method is employed to get the numerical solution due to the non-linearity. Further, the loading and shape iterative procedure are used to model the coupling relationship between the longline shape and hydrodynamic forces. The results suggested that this method has excellent global convergence and good accuracy for predicting the tension and shape of tuna longlines during fishing operation.