拖船回转机动状态下的拖缆暂态分析

拖船直拖到稳态定长回转过程中的拖缆暂态已有研究。对于大半径的拖船回转，Chapman大半径定长回转解法1]，假定拖体轨迹与拖体深度是单调指数关系。对于小半径的拖船回转，拖体的轨迹开始随着拖体深度的波动是一种螺旋线形状，最终趋于Chapman稳态回转值。本文通过定义了一个拖体深度与深度是单调与波动关系，提出了另一种确定Chapman理论大半径与小半径过渡值的方法。在考虑流的影响下的稳态定长回转时，没有求解稳态回转的方法。然而，拖体振幅是拖船回转半径和拖船速度的函数。依据稳态船体回转机动暂态分析来讨论单独360?和单独180?U型回转的动态特性，并得出一些有用的结论。对于某些回转半径而言，拖体所达到的深度比稳态回转所达到的深度大得多。对于180?回转半径小于拖缆长度的回转，拖体深度达不到稳态回转的深度。

Transient Behavior of Towed Cable during Ship Turning Manoeuvre

There have been some researches on the dynamics behavior of a towed cable system. Normally, the towed ship changed trajectory k form a straight tow to one involving steady circular turning at constant radii. For large-radius ship turns, we assumed the vehicle trajectory and depth to be monotonically and exponentially, the large-radius steady state turning solution refer 1]. For small-radius ship turns, firstly, the vehicle trajectory followed a corkscrew pattern with the vehicle depth oscillating about; finally decaying to the steady-state turning solution of Chapman (1984). We defined the change between monotonic and oscillatory behavior in the time history of the vehicle depth and offered a new method to measure the transition radius between large-radius and small-radius behavior. However, there was no longer steady state turning solution for steady circulation when took the current into consideration. The vehicle depth oscillated amplitude was a function of turning radius and tow speed. We discussed a single 360? turn and a 180? U-turn according to the transients of the steady turning maneuver and got some useful and practical conclusions. For some ship-turning radii, the vehicle maximum depth that was greater than the steady state turning depth. For a 180? turn and radius less than the tow cable scope, the vehicle never reached the steady state turning depth at all.