双桨双舵内倾船型的横甩失稳运动预报研究

Prediction method of the broaching of a tumblehome ship with twin propeller and double rudders

目前国际海事组织(IMO)已经发布了第二代完整稳性衡准骑浪/横甩直接稳性评估方法的最终指南,如何准确高效地数值预报骑浪/横甩运动是目前骑浪/横甩直接稳性评估方法中亟待解决的关键问题。本文构建一个纵荡-横荡-垂荡-横摇-纵摇-首摇六自由度运动耦合的数学模型,该数学模型首先在纵荡-横荡-横摇-首摇四自由度操纵性数学模型基础上考虑垂荡和纵摇运动的影响,采用基于加强积分的切片法求解垂荡和纵摇运动的幅值和相位,可以有效解决尾浪中高航速船舶直接耐波性时域计算容易发散的问题;其次,船舶在波浪中的Froude-Krylov力和绕射力是通过对船体平均湿表面进行压力积分获得的。同时,在数学模型中还考虑非线性水动力导数、静水横倾产生的水动力和非线性横摇阻尼等因素。在螺旋桨推力和舵力模型中考虑由于波浪粒子速度和船舶速度共存产生的水动升力的影响,舵力模型中还加入了垂荡、纵摇运动对波浪中双舵实时出入水导致的舵力动态变化。最后,以双桨双舵的ONR内倾船型为研究对象,开展尾斜浪中骑浪/横甩数值预报,分析船-波的初始相对位置对船舶骑浪/横甩运动的影响。计算结果表明,文中建立的六自由度骑浪/横甩数学模型具有足够的计算精度,可以用于骑浪/横甩的直接稳性评估。

At present,the International Maritime Organization(IMO)has issued the final guidelines of the direct stability assessment of surf-riding/broaching for the second generation intact stability criteria,and how to accurately and efficiently predict the surf-riding/broaching is a key problem to be solved for the direct stability assessment of surf-riding/broaching.So a surge-sway-heave-roll-pitch-yaw coupled mathematical model(6-DOF)is established in this paper.Firstly,the heave and pitch motions are considered in the surge-sway-roll-yaw maneuvering mathematical model,and the amplitudes and phases of heave and pitch motions are calculated by a strip method using an enhanced integrating method,which can solve the problem of diver-gence resulting from direct seakeeping calculation in time-domain for high speed vessel in stern-quartering waves.Secondly,the Froude-Krylov forces and diffraction forces are calculated by integrating the wave pressure up to the mean wave surface.At the same time,nonlinear hydrodynamic derivations,heel-induced hy-drodynamic forces and nonlinear roll damping are considered in the mathematical model.The hydrodynamic lift forces due to the coexistence of wave particle velocity and ship forward velocity are taken into account in the propeller thrust and rudder force model.And the real-time emersion of double rudders in waves is consid-ered in the rudder force model.Finally,a tumblehome ship with twin propellers and double rudders is uti-lized to study surf-riding/broaching in stern-quartering waves,and the effect of initial relative position of the ship to waves on predicting surf-riding/broaching motion is investigated.The computation results show that the established 6-DOF mathematical model has enough accuracy to be used for the direct stability assess-ment of the surf-riding/broaching failure mode.