摘要
本文研究了深海垂直杆件在波流联合作用下的波激-涡激-参激耦合振动特性。基于Hamilton原理,建立了垂直杆件的三维振动模型,考虑Morison力、涡激力和顶端变张力,对结构的波激-涡激振动和波激-参激-涡激联合振动进行数值模拟,求得杆件各点位移时历曲线,并针对时历曲线进行快速傅里叶变换得到能量频谱,从能量角度分析杆件振动特性。在此基础上,研究了振动幅值随流速、参激频率和参激幅值的变化规律。研究表明:在波流联合作用下,杆件振动出现非线性,轴向振动存在1/2和1/4亚频振动成分,拖曳力方向振动存在二倍波激频率成分;当涡泄频率接近杆件横向振动固有频率时,轴向振动和涡激振动振幅增加;存在参数激励时,杆件三个方向的振幅增大,振动对流速更加敏感;参激频率接近杆件固有频率时,轴向振幅和涡激振幅均增加,而当参激强度增加时,三个方向的振幅均增加,平衡位移不受影响。
This paper focuses on the coupled dynamic characteristics of a vertical flexible beam under waveinduced,vortex-induced and parametric excitations.The Hamilton variational principle is used to obtain the governing equations of motion and the boundary conditions,and the hydrodynamic effects are taken into account through Morison equation and vortex-induced forces to simulate the vortex-induced vibration with and without parametrical excitations.The nonlinear and coupled equations of motion are solved using the finite difference approach and Runge-Kutta method,the numerical results of three dimensional motion time history responses and corresponding power spectral densities are plotted and discussed.Special attention is paid to the effect of the parametric excitation frequencies and the amplitude of the top tension.The results show that under joint action of waves and currents,1/2 and 1/4 fractional harmonic axial vibrations and 2 super harmonic flow direction vibrations appear.When the vortex frequency is close to lateral natural frequency,the amplitudes of axial vibrations and vortex vibrations increase.Under parametric excitations,three dimensional responses increase and are more sensitive to flow speed.When the parametric excitation frequency is close to the natural frequency,the amplitudes of axial vibrations and vortex vibrations increase.When parametric excitation increases,three dimensional responses increase while equilibrium position keeps unchanged.
作者
刘浩宇
唐友刚
李焱
曲晓奇
LIU Hao-yu;TANG You-gang;LI Yan;QU Xiao-qi(School of Civil Engineering,Tianjin University,Tianjin 300072,China;State Key Laboratory of Hydraulic Engineering Simulation and Safety,Tianjin University,Tianjin 300072,China)
出处
《船舶力学》
EI
CSCD
北大核心
2021年第1期101-110,共10页
Journal of Ship Mechanics
基金
国家自然科学基金资助项目(51239008,51279130)。
关键词
深海垂直杆件
涡激激励
参数激励
动力分析
三维响应
vertical flexible beam
vortex-induced excitations
parametric excitations
coupled dynamic analysis
three dimensional response
