Influence Of The Breakwater Layout On The Hydrodynamic Performance Of Floating Structures

With the construction of islands and reefs in the south China sea,the safety of marine structures has been attracted more and more attentions.It is extremely dangerous to expose marine structures such as nuclear power platforms and semi-submersible platforms to the severe sea environment.Therefore,it is necessary to protect the offshore platforms in operation.The existence of the breakwater can greatly improve the hydrodynamic performance of the platform's motion response,air gap,etc.,thereby improving the safety of the marine structure.In order to study the hydrodynamic properties of marine structures in the protection of breakwater,based on ANSYS 18.0 fluid analysis module,this paper studies the hydrodynamics of marine structures with different breakwater arrangements.The main work of this paper is as follows:(1)This paper first summarizes a large number of domestic and foreign literatures within the present research field.The research status of numerical tools is mainly analyzed,and the wave-making and wave-eliminating methods involved in numerical wave tank are investigated.On this basis,the present situation of the research of the hydrodynamic problems in the interaction of wave and structure,such as the wave run-up,the forces and the air gap response of the offshore platform are investigated and studied.At last,the arrangement strategy of breakwater and the cases of port construction are summarized.(2)Based on theories of hydrodynamics,numerical simulation methods involved in this paper are intreduced.The basic governing equations of fluid motion,the advantages and disadvantages of different turbulence models,numerical discrete methods,boundary conditions,free surface treatment involved in two-phase flow problems,dynamic mesh technology involved in body motion are introduced in details.(3)Based on ANSYSY FLUENT 18.0,a numerical wave tank with wave-making and wave-eliminating module was established.With the User-Defined Functions program in solver,velocity inlet boundary and piston like wave-maker have been implemented.The second-order Stokes wave has been simulated by the piston like wave-maker.Wave elimination is employed by modifying source term of the momentum equation in the wave elimination region.Finally,the wave attenuation of the numerical tank with wave-making and wave-eliminating modules was studied,and the verification of the numerical tank has been presented by the standard calculation proposed by the ITTC.(4)Based on the existing research experience,the hydrodynamic problems such as wave run-up,motion and air gap of the offshore platform with six column were studied.Firstly,the time history of wave run-up is used to describe the influence of wave interaction between the columns and then the phenomenon of wave amplitude enlarged by the existence of submerged colum is discussed;Then,the wave run-up of front and rear columns caused by the change of incident wave parameters is described,and the hydrodynamic phenomena in the wave run-up are described in detail.At last,the minimum air gap of the platform is studied.(5)Based on the above conclusions and using same model,the motion response and wave run-up of the semi-submersible platform with two kind of breakwater layout are studied.The influence of the distance between breakwater and platform on the hydrodynamic performance of the platform is analyzed.Then the motion of the platform and the relative wave height on the column are studied with different wave periods.Finally,the hydrodynamic effects on platform of symmetrical and asymmetrical arrangement of breakwater are compared.