Investigation Of Dipole-source Distribution In Motion And Wave Load Calculation

Motion and wave loads of floating body is quite vital in wave-body interaction problem.Boundary element method is popularly applied in solving velocity potential, among which source distribution model is favored as its easy solution of source strength. However, source distribution model do not have actual physical meaning and earns a poor accuracy of tangential derivatives of velocity potential. This thesis used the dipole-source distribution model which was derived from Green identity integral. Based on free-surface Green function of infinite water depth, this original boundary element integral was solved by constant element and high-order element in thesis, respectively ?First of all, Chebyshev series was applied in numerical approximation of free-surface Green function and its higher order derivatives(second order derivatives at least) in infinite water depth as its high convergence. Numerical results showed a high accuracy of algorithm of the Green function and its high order derivatives.Then, constant element was adopted in this dipole-source distribution boundary element integral by using the Green function. The non-dimensional hydrodynamic coefficients on submerged sphere and hemisphere were calculated and investigated to verify the Rankine part integral and the wave oscillate part integral, respectively. Besides, a cylinder was adopted for estimating the higher order derivatives of velocity potential as its velocity potential has a analytical expression.After that, higher order element was utilized in solving dipole-source distribution boundary element integral by using the free-surface Green function. Several similar geometry objects in research of constant element boundary integral were calculated. Numerical result showed a great convergence and accuracy in program produced by author.Motions of two Wigley ships were calculated and had a good accordance compared with experimental values. The mean drift force program was verified by a submerged sphere.Finally, a floating structure FPSO was evaluated by constant element and high-order element mentioned above respectively, whose hydrodynamic coefficients, motions and drift forces were investigated.