Research On Response Regularities Of The Collision Of Deep Sea Risers

With the continuous development of the social economy,the demand for energy is still rising year by year at home and abroad.Facing the severe status of insufficient reserves and difficult exploitation of land energy resources,the ocean with abundant energy resources is bound to become the principal pathway for energy development and utilization in the future.With the development of resources exploitation progressively advances to the deep sea,the design and optimization of the deep sea platform and its ancillary equipment has become one of the hot topics of research in the field of ocean engineering.Marine risers are an important component of the drilling platform in deep water.The collision may occur between the adjacent risers under the combined effect of external load and fluid-solid interaction,the service life of risers will be affected and the secondary disasters will be occurred.The purpose of this paper is to reveal the inherent laws of the dynamic collision response of the deep sea risers under complex working conditions,it is expected to provide reference and basis for the design and improvement of the deep-sea riser system from now on.In this paper,the basic theory and research methods of the riser collision analysis were summarized,and the internal mechanism and inducing factors of the collision between the risers were studied.The Fluent software was used to simulate the static flow process around the tandem double risers,and the effects of riser spacing,Reynolds number and riser diameter ratio on the riser motion and flow characteristics were analyzed.Thus the action mechanism of shadowing effect of the wake flow field of upstream riser and VIV on the collisions between risers was obtained.The ABAQUS software was used to simulate the local collision course between risers.The sensitivity factors that may have an impact on the collision characteristics of risers were summarized,after that the impact response characteristics of the deep sea risers under the different parameters were compared and analyzed in the ideal environment and the external water environment,respectively.In addition,considering the actual force of the risers,the Co-execution coupling analysis method in ABAQUS/CAE was used to study the fluid-solid coupling interaction between the riser and its internal fluid,it will contribute to the further perfection of the riser collision theory.At the end of the paper,based on numerical simulation and quadratic regression analysis,a response surface analysis method of riser collision was proposed,which included four factors and three levels.For the nonlinear collision procedure of risers,the BOX-Behnken design method of Design-Expert software was used for response surface analysis between experimental factors and indexes.Through the work above,the response surface models were obtained.Ultimately,the response surface analysis method and the resulting models were validated by its comparison with the results of the finite element calculation.