Dynamic Analysis Method Of Subsea Manifold Under Impact Of Falling Objects Based On Hybrid Surrogate Model

Subsea manifold is the key equipment and important node of subsea production system.Falling objects at sea are one of the main factors leading to the failure of subsea manifold.The dynamic analysis of subsea manifold under the impact of falling objects can provide the basis for the optimization design of subsea manifold structure,and also provide data support for the reliability analysis of subsea production system.The collision process between falling objects and subsea manifold is a highly nonlinear and complex dynamic problem.Based on the full-scale finite element model,the dynamic analysis of subsea manifold under the impact of falling objects has the problems of long time-consuming finite element simulation and high computational cost.In order to solve this problem,this paper introduces the surrogate model method instead of the finite element method to analyze the dynamics of subsea manifolds.Considering the limitations of single surrogate model in the face of complex problems,the hybrid surrogate model modeling method of dynamic response of subsea manifolds under the impact of falling objects is studied.Based on the hybrid surrogate model method,the dynamic response analysis of subsea manifolds under the impact of falling objects is carried out.The main work of this paper is as follows :Firstly,aiming at the problem that the accuracy of dynamic analysis results is damaged in the non-full-size model,a full-size finite element model of subsea manifold is established.Considering the influence of ocean current impact load on the pipe system under normal working conditions,in order to comprehensively analyze the impact of ocean current load on the pipe system,the ocean current impact load is applied in the X and Y directions of the pipe system respectively,and the finite element static analysis of the pipe system under ocean current impact is simulated.The results show that the pipe system model meets the design requirements and provides the pipe system model for the subsequent finite element analysis of subsea manifold dynamics.Secondly,in order to analyze the impact of falling objects on subsea manifolds,considering the differences in the types of falling objects,the finite element models of collision between Hall anchor,circular tube,sphere and subsea manifolds are established respectively,and the finite element collision process between four types of falling objects and subsea manifolds is simulated.The results show that the greater the weight of the falling object,the greater the impact on the manifold;the smaller the collision contact area between the falling object and the manifold,the greater the deformation of the manifold;the thicker the top protective plate of the manifold is,the greater the energy absorbed by the falling object is,and the thickness of the plate is the best choice when it is 5-7mm.However,there is a problem that the full-size subsea manifold model is too large and the finite element simulation time is too long.Finally,aiming at the problem that full-scale modeling leads to long time-consuming and high computational cost of finite element simulation,SVR(Support Vector Regression),KG(Kriging)and RBF(Radial Basis Function)surrogate models are introduced to improve computational efficiency.The results show that the KG model has the highest accuracy,followed by the RBF model,and the SVR model has the lowest accuracy.Furthermore,considering the limitation of data fitting of single surrogate model,the prediction accuracy is not accurate enough.A hybrid surrogate model of dynamic response of subsea manifold under impact of falling objects is established by using Cramer average weighting method.The hybrid surrogate model is used to predict the dynamic response index,and the prediction accuracy and modeling cost are compared with KG prediction results,RBF prediction results and real values respectively.The results show that the average calculation accuracy of the hybrid surrogate model is 10.12 % higher than that of the single surrogate model,and the calculation efficiency is 81.24 % higher than that of the finite element method alone.After that,based on the hybrid surrogate model,the dynamic response analysis of the subsea manifold under different plate thicknesses is carried out.The results show that when the protective plate is 8mm,there is no significant change in the impact deformation caused by falling objects on the subsea manifold,the reduction of the acceleration value of the pipe system interface and the energy absorption value of the protective plate.Therefore,the optimal thickness of the top protective plate of the subsea manifold is 8 mm.