Numerical Simulation of Wave Loading on FPSO in Various Wave Conditions

摘要

In the design of Floating Production Storage and Offloading facilities (FPSO), it is important to predictrnthe seakeeping parameters like FPSO motions. This paper focusses on the prediction of FPSO motions andrnwave impact loads in various irregular sea waves and proposes a Computational Fluid Dynamics (CFD)rnmodel. Accurate prediction of FPSO motions and wave impact loads requires the accurate prediction ofrnwave kinematics. Waves generated by winds blowing over the water surface in real oceans are shortcrested,rnso the dynamic responses of the moving structure will be very different in long crested andrnshort-crested waves. In this paper, we have verified the pure propagation of oblique short-crested randomrnwaves in numerical wave tank with the analytical results, which serves as the basis of more complexrnanalysis including ship hull interaction with waves.rnThe proposed CFD model uses Multiphase Volume of Fluid Model (VOF) along with Six Degrees ofrnFreedom Model (6DOF) to predict the hydrodynamic forces and the ship responses. Long crested andrnshort-crested random waves are simulated in a numerical wave tank, where boundary conditions for freernsurface profiles and velocities are imposed at the velocity inlet boundary using Jonswap frequencyrnspectrum and cosine-2s directional spreading function.rnWave slamming loads and the structural responses depend on many factors, like sea state, FPSO speed,rndraft, wave heading angle, local structure etc. In this paper, we have analyzed the wave slamming on arnmoving FPSO for different sea states (unidirectional, multi directional with 45 deg and 90deg angularrnspread) and studied the resulting hydrodynamic forces and related structural interactions. Ship motionsrn(heave, pitch and roll), vertical accelerations, pitch velocities, roll velocities and the wave impactrnpressures are compared among different sea states.