考虑艏摇的半潜式平台涡激运动试验研究

Tests for VIM of a semi-submersible platform considering yaw motion

为研究半潜式平台的涡激运动特征,进行了水槽模型试验研究。测试了流向角为0°、15°、30°及45°时,在不同来流速度下半潜式平台的横荡、纵荡及艏摇运动响应;并以艏摇运动为重点,从响应幅值、运动频率等角度出发,探讨其涡激运动的关键特征。结果表明:在不同来流方向情况下,半潜式平台均未发生明显的频率锁定现象。当流向角为0°和15°时,平台三自由度响应随约化速度的增加近似呈线性增大的趋势;当流向角为30°和45°时,在约化速度4~10附近平台响应出现了明显的共振现象,并在此现象结束后响应大幅减小,之后,随着约化速度的增加再次大幅增大。除个别工况外,艏摇与横荡均高度耦合,其响应频率主峰值基本保持1∶1关系;艏摇固有周期对平台三自由度运动频率及幅值影响均不明显。流向角为45°时,平台的艏摇运动最为剧烈,在各个约化速度下响应幅值均数倍于其他流向角。另外,在0°流向角时观察到了“驰振”现象;15°流向角的多个约化速度下观察到了“自激”现象。

Here,in order to study vortex-induced motion(VIM)features of a semi-submersible platform,its flume model tests were conducted.The motion response amplitudes and frequencies of its sway,surge and yaw motions were measured under different incoming flow velocities and flow angles of 0°,15°,30°and 45°to explore key characteristics of its VIM.The results showed that there is no obvious frequency locking phenomenon in different incoming flow directions;the platform’s 3-DOF response almost linearly increases with increase in reduced velocity when the flow angle is 0°and 15°;the platform’s response has resonance phenomenon when the flow angle is 30°and 45°and the reduced velocity(Ur)is close to 4~10,and the response significantly decreases after the resonance phenomenon is over,then it sharply increases again with increase in reduced speed;except under few working conditions,the platform’s sway and yaw motions are highly coupled and their response frequencies’main peaks remain the relation of 1∶1;the natural period of yaw has almost no effect on the platform’s 3-DOF motion frequency and amplitude;when the flow angle is 45°,the platform’s yawing motion is the most strenuous,its response amplitude is several times of those for other flow angles at any reduced speed;in addition,galloping phenomenon is observed when the flow angle is 0°;self-excitation phenomenon is observed when the flow angle is 15°at multiple reduced speeds.