Study On Hydrodynamic Oscillation In A Narrow Gap Between Side-by-side Floating Structures

In the offshore oil and gas exploitation and transportation,the problems of multi floating structures are usually encountered.In some conditions,between the floating structure will seriously affect the strong coupling between offshore operation safety and stability of the situation.The viscous flow theory and computational fluid dynamics(CFD)based on the theory of free surface was captured by VOF method,CFD commercial software Flow3 D based on the two floating structure of narrow gap between flow problems are analyzed,in order to study the narrow wave oscillation phenomena in the.The main achievements are as follows:(1)This paper introduces the common multi floating body system,and summarizes the research status of multi floating body hydrodynamic interference both at home and abroad.(2)The interaction analysis model of the adjacent floating structure is established,and the numerical simulation of the flow field in a narrow gap is carried out by means of two-dimensional and three-dimensional numerical wave tank.The calculated results are consistent with the experimental results in the relevant literatures,which verifies the accuracy and reliability of the method and numerical calculation.(3)Firstly,the mesh convergence of the model is analyzed,and the optimal meshing scheme is selected.The flow field between two fixed structures is analyzed.Through the analysis of two aspects of wave elevation and the fluid movement in the narrow gap found:when the narrow spacing is the same,the fluid movement in the narrow gap is different in different wave period,when the incident wave reaches resonance cycle,narrow flow field will appear significant wave rise phenomenon;with narrow spacing increases,resonance periodic also increases.When the wavelength is too large,narrow to the shadowing effect in the narrow gap between the inner and outer flow field,does not appear obvious wave elevation.When the wavelength is further reduced,less than 1 times of the captain,the waves can enter the narrow internal and surface elevation at narrow spacing is small,narrow gap between the strong agitation of fluid.There may be one or more peak points in a narrow gap,which are related to the aspect ratio L / B and the wavelength ratio ? / L.(4)The full coupling problem of wave / multi floating motion / narrow gap oscillation is analyzed numerically.The differences found by comparing the single floatingbody and a plurality of floating bodies in motion and force on the narrow gap between: due to the influence of fluid movement,free floating structure motion and force change greatly,that narrow fluid movement is not negligible influence on the structure.(5)By changing the direction of the incident wave,the oblique wave and transverse wave,the numerical simulation of two floating structure of narrow gap between the flow field,flow field analysis of wave and wave oblique wave rise,narrow internal fluid motion.Combined with the results of the wave calculation,comparative analysis of the three wave downward floating body movement and stress situation,draw oblique wave compared to other conditions more dangerous conclusions.