半潜式平台非线性回复力矩对低频纵摇的影响

Nonlinear restoring moment of semi-submersible and its effect on low frequency pitch motion

为了系统分析非线性因素对半潜式平台低频纵摇运动的影响,通过理论推导和数值分析获取平台由于浮心与重心变化、立柱水线面改变及横撑出水所引起的回复力矩.将已建立计算方法应用于ExWave模型试验平台,采用考虑和忽略横撑出水两种仿真模型,通过时域模拟来分析和对比横撑出水对纵摇运动的影响.计算结果表明:横撑出水会导致纵摇运动正向极值增加而负向极值减小,说明该物理现象对纵摇运动既有抑制作用又有激励作用,因此在恶劣海况条件下考虑横撑出水是非常必要的.

In order to evaluate the nonlinear effects on the low frequency pitch motion of the semi-submersible,through theoretical derivation and numerical analysis,the recovery torque of the platform caused by changes in buoyancy center and center of gravity,changes in column waterline surface,and lateral support water outflow was obtained.The established calculation method was applied to the ExWave model test platfor,using two simulation models:considering and ignoring the lateral brace water outlet.The impact of lateral brace water outlet on pitch motion was analyze and compare through time-domain simulation.The results show that the brace emergence would result in higher extreme pitch on the positive side and lower value on the negative side.It is indicated that this phenomenon would play both inhibiting and stimulating roles on the pitch motion,and therefore it is essential to take it into account under severe environmental conditions.