Research On The Influence Of Side Shape Of An Innovative Sandglass-type Floating Structure

With the offshore oil and gas exploitation to the deep sea which is under even worse environment,FPSO has become the first choice for deep-sea oil and gas exploitation.for its low initial investment,high storage capacity,fast production,reusability,short construction period,wide application of depth,mobile flexibility,and other performance advantagesThe main work of this paper is to analyze and sum up the performance limitations of the exisiting ship-type and cylinder-type floating structures.Then,based on the Innovative sandglass-type FPSO with linear side which considers improving hydrodynamic performance as decisive element in the conceptual design of floating structure,we study the innovative sandglass-type FPSOs with curve sides which attempts to keep existing performance advantages of the linear-type FPSO.Furthermore,it aims to further improve the hydrodynamic performance of linear-type FPSO,ensuring structures' sufficient stability.So that we could find a complete set of engineering equipment for the development of deep-sea oil and gas.The main contents of this paper include the following aspects:Firstly,we strive to fix the shape parameters of underwater floating body of linear-type model: waterline radius,draught,bottom radius,only to change the shapes of the curve side to analyze qualitatively the effect of concave and convex shape upon the hydrodynamic performance.We drawed the conclunsion that 3 main floating body models: spline-type model,parabolic-type model,oval-type model under above limitations cannot meet the requirement of the same displacement and the minimum frequency of the heave motion RAO as the linear-type model.Based on the design principle of "the same displacement and minimum frequency of the heave motion RAO as the linear-type model",we determine to change the underwater shape parameters to obtain different kinds of curve-type models.Then,the hydrodynaminc analysis software AQWA is used to further analyze the heave motion performance and stability of these models.According to the analysis,we put forward a more complete design princle of "enough stability,the same displacement and minimum frequency of the heave motion RAO as the linear-type model and better second peak of heave motion RAO".And we find the concave oval-type model of the design criteria,by comparing it with the linear-type model in typical working conditions,better heave and pitch motion performance of the concave oval-type model has been verified.Finally,versus the specified new concept of sandglass-shape floating structures with concave oval types,we use AQWA to analyze the influence of underwater shape parameters on the second peak of the heave motion RAO.Base on the results,we find concave oval-type model which meets the design principle of "enough stability,the same minimum frequency of heave RAO and displacement as the linear-type model and the optimal second peak of heave motion RAO".Also,we have verified its better heave and pitch motion performance in typical conditions versus the linear-type model.