Simulation Of Numerical Wave And Its Application Research On Dynamic Characteristics Of Offshore Platform

Accurately calculating wave load for deepwater jack-up drilling platform has been aproblem in the field of marine engineering for a long time. Improving the calculationprecision of wave load has important and practical significance for ensuring the offshoreplatform security and economy. Taking a certain type of jack-up drilling platform as theresearch object in this paper, the wave load for truss-type leg and platform hull is separatelycalculated by using the CFD software Fluent to generate three-dimensional numerical waveand applying the method of fluid-solid interaction. The main research work in this paperincludes:(1) The basic theories used in this thesis are elaborated, including wave theory andfluid-solid interaction theory. In the wave theory part, the basic equations of linear wave andStokes wave are mainly given, and in the fluid-solid interaction theory part, the finiteelement method is used to deduce the fluid-solid interaction system motion equations.(2) Imitating the physical wavemaker principle, the wave equation of linear wave isdeduced based on the periodic moving piston method. Using the UDF macro of Fluentrealizes the piston sinusoidal motion, porous medium aborbing wave and third-order Stokeswave simulation. The unsteady turbulent flow field is acquired by using pressure-basedsolver, VOF algorithm and pressure-velocity coupling PISO algorithm. Three-dimensionalnumerical wave whose wave height is12m is realized, including linear wave and third-orderStokes wave. After the comparison of numerical and theoretical wave, it is proved that usingthe CFD method to simulate numerical wave is appropriate.(3) Three-dimensional finite element model of jack-up drilling platform is established,and using bonded contact between the truss-type leg and platform hull simulates pinion andrack contact form of elevating device. Then modal analysis of jack-up drilling platformunder gravity load is done, the results show that natural frequency of jack-up drillingplatform is different from the wave frequency, avoiding casuing resonance.(4) Wave load calculation method based on advanced CFD technique is proposed, andthe wave loads for truss-type leg which is small scale structure and platform hull which islarge scale structure are separately calculated. At the same time, the flow field characteristicaround truss-type leg and platform hull is separately analysised as well as the structure’sstress distribution. The results show that it is important to pay attention to bending moment for truss-type leg and turning torque for platform hull when designing a jack-up drillingplatform.