Nonlinear Diffraction Effects Around a Surface-Piercing Structure

In the present paper the interaction of a wave system with a fixed body is studied. The wave diffraction in finite-depth water around a vertical cylinder and a simple shaped shoal is computed; the results are discussed in comparison with analytical solutions and experimental data. The linearized and the fully nonlinear mathematical models are studied in the frame of irrotational incompressible flow hypothesis. The numerical solution is gained by means of an integral formulation. The body surface is discretized by a classical zeroth order panel method, whereas a desingularized scheme is implemented on the free boundary. A time marching Runge-Kutta algorithm is used for the computation of the wave pattern and the velocity potential at each time step. The simulation of wave diffraction around fixed obstacles confirms and extends the theoretical results of the second order analysis (Kriebel 1990, 1992): The linear model yields a very good estimation of the force amplitude acting on the body, while the wave profiles are poorly evaluated when compared with the fully nonlinear simulation and the experimental data.