Abstract In present paper, both potential-flow and viscous-flow solvers have been used in the numerical analysis of wave-structure interactions. In the first case, surface elevations around a fixed truncated circular column have been investigated and numerical results have been compared with experimental data. Nonlinear wave forces acting on the same column have also been estimated. In the second case, the roll motion of a rectangular floating structure in regular wave has been simulated.

ABSTRACT: A time-domain higher-order boundary element method (HOBEM) is used to simulate the linear and fully nonlinear waves in a threedimensional numerical wave tank (NWT). In order to eliminate reflective waves at the incident boundary and output boundaries, damping layer combined with a nonreflective wave generator, which is composed a series of vertically aligned point source in the computational domain, is applied. The governing equation is solved at each time step by using Rankine sources distributed on all the boundaries. Based on the image theory, a new Green function is applied in the whole fluid domain so that the two lateral surfaces and bottom are excluded. Numerous numerical experiments, on linear and fully nonlinear wave propagation in a wave tank with and without fully reflective wall, demonstrate that the present approach is effective in generating an arbitrary wave profile without reflection not only at the open boundaries but also at the wave generator. It is furthermore shown that scattered waves can pass through the area of generation without significant reflection and the process of generation is not affected by the scatted waves. INTRODUCTION With the increasing use of numerical techniques and computers during the past two decades, it is possible that the numerical wave tanks are used to investigate wave interaction with structures and the considerable efforts have been devoted to developing increasingly accurate and efficient numerical wave tank to investigate various fully nonlinear water wave problems at sea. Such numerical results have been shown to model the wave propagation and overturning in deep water (Dommermuch et al ., 1988), wave shoaling up to breaking over slopes (Grilli et al ., 1994), wave loads on objects (Zhang et al., 1996; Boo and Kim, 1997; Kashiwagi, 1996) and floating body motions (Isaacson,1982; Kashiwagi, 1998) etc.

ABSTRACT: This paper deals with the manners for generation of nonlinear shallow water waves In the laboratory. The displacements of the wavemaker plate for producing onoidal and solitary waves are derived based on the kinematic boundary condition. The experimental results show that well formed onoidal and solitary waves can he reproduced by means of these displacements. Finally, the applicability of the wave theories is discussed from the view point of the wave profile and horizontal water partical velocities. INTRODUCTION It Is very Important to generate nonlinear shallow water waves In the laboratory and to measure water particle velocities Induced by waves for the Investigations of various phenomena on coastal engineering such as wave forces, littoral drifts and so on. It has been known experimentally (Goda.1967) that It is extremely difficult to generate shallow water waves of finite amplitude In a manner that a wavemaker oscillates sinusoidally. The authors of the present paper noted that as a ratio of wave height to water depth is greater than 0.45.the long wave produced by the sinusoidally moving wavemaker could simply propogate In a short distance and break quickly. The breaking may be due to the reason that the velocity of the wavemaker plate in simple harmonic motion is not consistent With the water particle velocity of the long wave near the wavemaker plate. Therefore a correct displacement of the wavemaker plate IS necessary to generate shallow water waves In the wave tank. Secondly the experimental procedure is described and the experimental results are compared with the available wave theories such as Stokes wave theories, onoidal wave theories, the stream function theory, and solitary wave theories. THEORETICAL CONSIDERATION Consider the wave generation process In a shallow water tank. The wave Is generated by a wavemaker and propogates along the tank.