多激励工况下重吊型半潜船振动特性

Vibration Characteristics of Heavy Lift Semi-Subvessel under Multiple Excitation Conditions

动态定位是海洋工程船舶的一种特别的定位方式。在动态定位工况下,船舶主推进器、可伸缩推进器和侧推进器同时运转,激励源增多,在周围水流的作用下,将较大的振动能量传递给船体,引起推进舱及上层建筑甲板产生较大的振动,严重影响船舶的舒适性。目标船为重型起吊船,在主甲板右舷处设置有5 000 t的起吊装置,在艉部配备4台主推进器,艏部配备2台侧推进器及2台可伸缩推进器。定位工况下,需同时开启这3种设备,船舶处于多激励状态,易引发上层建筑较大的振动。文章采用有限元方法,建立目标船的三维数值模型,分析了其振动的固有频率及模态,计算了多激励工况下整船的振动响应。结果显示:目标船自由振动的前6阶固有频率较低,均已避开各激励源的风险频率范围;多激励工况下,以可伸缩推进器和艏侧推器的激励为主,各层甲板速度响应的最大值出现在11 Hz附近,响应曲线出现多个峰值,振动耦合性增强,对加权值的影响增大,但最终均能满足舒适性相关的标准限值。

Dynamic positioning is a special positioning method for Marine engineering ships.Under the DP condition,the main propulsion,retractable thrusters and bow thruster of the ship run at the same time which make the excitation sources increase.Under the action of the surrounding water,the larger vibration energy is transferred to the ship,causing the larger vibration of the propellant tank and the superstructure deck,which seriously affects the comfort of the ship.The target ship is a heavy lifting vessel with 5000 t lifting gear on the starboard side of the main deck.In addition,four main thrusters are provided on the stern,two side thrusters and two retractable propellers are provided on the bow.Under the DP condition,all three devices need to be turned on simultaneously,the ship is in a state of multiple excitation which easy to cause the vibration of the superstructure,therefore,this paper use the finite element method to establish 3D numerical model of the target ship.Then the natural frequencies and modes of its vibration are analyzed,and the vibration responses of the whole ship under multiple excitation conditions were calculated.The results show that the first six natural frequencies of the free vibration of the target ship are low,which have avoided the risk frequency range of each excitation source.Under multiple excitation conditions,the maximum velocity response value of each deck appears around 11 Hz,and multiple peaks appear in the response curve,which resulted in enhanced vibration coupling and increased influence on the weighted values.However,all of them finally met the comfort related standard limits.