The Study Of The Vortex Motion Response For Deep Draft Semi-submersible

With the increasing demand of oil and gas,the exploration technology of oil and gas resources is developing,and the Semi-submersible platform has been widely used in deep sea.Because the development of the offshore oil and gas exploration area extend to the deep water continuing home and abroad,bad weather occurred frequently,the engineering application of Semi-submersible platform is also facing serious challenges undersea.It is a very important problem for the international marine engineering to predict and improve the hydrodynamic performance of the platform,to improve the survivability and operational efficiency.Increasing draft is one of the effective ways to improve the vertical motion performance of Semi-submersible platform.However,when the design draft of Semi-submersible platform increases,that named a so-called deep draft Semi-submersible platform.The fluctuating pressure caused by vortex shedding has increased,The effective excitation of vortex motion increased also,so the vortex motion has become more obviously.Because of it,the study of vortex induced motion of deep draft Semi-submersible platform,Focus on the origin,evolution and response characteristics of vortex induced motion,and the fatigue damage of anchor chain and marine riser,it is of great significance for the design and construction of deep draft Semi-submersible platform.In this paper,based on the understanding of the computational fluid dynamics and the theory of the vortex flow around a single column and the Semi-submersible platform.Using computational fluid dynamics software(FINE/Marine)to carry out two dimension and three-dimensional simulation,there are two platform models(fixed mode,mooring mode)simulated,and gives the research fluid force coefficient,vortex shedding frequency,motion response analysis and so on.The conclusions of the research are as follows:Through the calculation of different Reynolds number of single cylinder flow simulation,get some regular pattern of the vortex shedding patterns,lift and drag coefficient and vortex shedding frequency with different velocity.Some conclusions about the dynamic characteristics of cylindrical have been obtained.Through the establishment and numerical simulation of three dimensional model of deep draft Semi-submersible platform,we have changes about coefficient of drag and lift,vortex shedding frequency,the distribution of lateral pressure coefficient along the circumferential direction,transverse and longitudinal motion amplitude,and the amplitude of self-locking.