Numerical Investigation Of Vortex-induced Motion Of Buoyancy CAN

Buoyancy can(BC)is a common structure in ocean engineering.Under inflow conditions,the wake field of BC will produce periodic vortex shedding,which will cause vortex-induced motion(VIM)of BC.The displacement of BC affects the tension and movement of the riser,which will lead to fatigue damage of the riser.At present,the research on VIM in industry and academia is mostly concentrated on the platform,and the research on the VIM of BC is just startup.Therefore,this paper carries out researches on the numerical simulation of VIM of BC,and offers a reference for the model test and numerical simulation of BC in the future.The solver applied in this work is the naoe-FOAM-SJTU solver developed by our research team based on the open source toolkit OpenFOAM.The shear stress transport(SST)delayed detached-eddy simulation(DDES)method is utilized to deal with the flow separation.Conventional dynamic mesh is not able to perform large amplitude rotation due to the excessive mesh distortion.In this work,overset grid method is used to avoid this problem.The main research content of this paper includes the following three aspects:First of all,in order to explore the influence of the free-end on the VIM,the numerical simulation of the single free-end cylinder is carried out.The reliability of the numerical method used in this work is verified by comparing the numerical simulation results with model test results.Then,by analyzing the two-dimensional vorticity field distribution at different sections of the single free-end cylinder under static state and VIM state,it is found that the free-end structure not only affects the vortex shedding of cylinder,but also affects the distribution of the shear layer in the wake field.Secondly,the initial computational model of BC released the degrees of freedom(DOF)in inline,crossflow,heave,and yaw to analyze the characteristics of yaw motion.The influence of the yaw motion on the VIM is analyzed by comparing the VIM responses of the release and fixed yaw DOF BCs.Furthermore,the mechanism of vortex-induced rotation(VIR)is analyzed by the results of the shear stress distribution and forced-motion numerical experiments of BC.Finally,a numerical simulation pertaining to VIM of BC with six DOF is performed.By comparing the results of the inline and crossflow displacement of the model test and the numerical simulation,the sources of error in the numerical experiments are analyzed.Then,according to the displacement data and distribution of vorticity around BC at different reduced velocities,the roll and pitch characteristics of BC and the vortexshedding mode in the wake field are explored.The research of this paper not only can be applied to explore methods to reduce the amplitude of VIM of BC,but also offers a reference for the subsequent investigation of the numerical simulation of VIM and the mechanism of VIR.Therefore,the work of this paper possesses both engineering and academic significance.