Wave Loads On Arbitrary 3D Objects In The Flume

Based on the potential flow theory and making use of an open-sea Green's function with infinite images about side walls of flume, this paper presents theory study and numerical simulation about wave loads on arbitrary 3D objects in the flume in linearity frequency-domain.Taking 3D Laplace equation as governing equation and applying to the second-order Green identity, an integration equation is founded in linear frequency-domain. To solve this integral equation, meshes have to be divided on the free surface, side-walls of flume and sea bed. Therefore, enormous computation cost and computer storage are needed in solving integral equation. In order to overcome the discussed difficulty, we firstly study two numerical methods of flume Green's function satisfying the free-surface boundary conditions. One is the rapid convergent numerical method which satisfies the free-surface boundary conditions and side-wall condition put forward by Linton and the other is an open-sea Green's function with infinite images about side walls of flume presented by John, simplified as image flume Green's function. Numerical experiments have been carried out and the results indicate that Linton's rapidly convergent numerical method is just limited to a small scope. Therefore, it is suggested that the image flume Green's function is used to solve the wave action upon structures in the flume with constant depth and width. So we can mesh only in the body then reduce the amount of lineal functions.In the case of the above equations only integrated on body, a simple Green's function, which corresponds to an infinite sum of images of sources and their reflections about horizontal seabed, is used to found an integral equation inside the body. Then a boundary integral equation without solid angle coefficient can be deduced by connecting integral equations inner and outer the calculation domain. The velocity potential on the body can be obtained by solving the boundary integral equation descritised by HOBEM. Through the movement equation of rigid body, the response amplitude can be obtained. In all a new high-order boundary element method is found, which can calculate wave forces on arbitrary shape three-dimensional objects in flume in linear frequency-domain.The wave loads on some familiar three-dimensional objects in flume are computed in this paper, and the corresponding results on vertical cylinder are compared with analytical solutions provided by Yeung and Sphaier. The good agreements show that the present scheme and the image Green's function used in this paper are exact and efficient. The...