Wave-induced Force Dynamics Analysis of Tension Leg Platform

Abstract

This work analyses the dynamic response of Tension Leg Platform, TLP under sea wave induced forces with the aid of fluid dynamics modified Morison equation, single degree of freedom mass spring damper theory, and the Runge-Kutta ode45. Specifically, we employ the modified Morison equation to calculate the sea wave forces acting on a cylinder hull of the TLP. Two types of sea wave characteristics are analysed including sea waves in the South China Sea to compute the waves loading on the hull. Evaluated results are incorporated into the equation of motion of the platform, modeled as a single degree of freedom mass-spring-damper system to obtain the platform displacement at x-axis direction. The results showed that the dynamic response of the platform under the influence of sea wave A exhibits a displacement of 0.02 m in the direction of wave propagation parallel to the x-axis of the platform. Meanwhile, sea wave B manifests a magnitude at least twenty times larger compared to sea wave A, resulting in 0.5 m displacement in the same axis direction. We further examine the consequence of velocity profile of sea waves on displacement and time taken for a complete vibrational cycle. A parameter-fed CFD simulation with Star-CCM+ shows clear dynamic response of the TLP when acted upon by sea wave A. Obtained results indicate the importance of materials selection for construction of the hull tendons based on the motion of the hull and gives a fair estimate for cyclic loading on the tendons throughout the life cycle of the platform.