The magnitude of impact force of highly nonlinear waves is very important in designing ocean structures. Using a numerical program based on N.S. equations, the impact forces of steep waves generated by a numerical wave maker can be studied. To validate numerical code, single frequency waves are generated and compared with analytic solution. The arbitrary steep waves are generated by the superposition of each wave and the results are compared with the experiment that shows an acceptable agreement. Wave loads acting on vertical cylinders are very complex and they can be simulated with multi-block grid method that can generate very complex geometries. Also the smooth wave profiles and the pressure contours across blocks can be obtained with multi-block grid system.
Studies on the impact forces of the freak waves to ocean structures have been presented. Natvig(1994) has pointed out that the ringing of structures can be occurred by nonlinear and un-symmetric freak waves. Hongli Pang et al.(2004) have simulated non-linear wave loads on small diameter vertical cylinder in freak waves by boundary element method where freak waves were generated in a two dimensional numerical wave tank. The results showed that wave loads were highly nonlinear and impulsive. And the high frequency components were included in wave loads inducing the ringing of structures.
In this study, a numerical program based on N.S. equations is developed to investigate impact forces of highly nonlinear waves to vertical cylinders. Waves can be generated by a numerical wave maker. The multiblock grid method is applied to simulate the complex geometries around vertical cylinders in numerical wave basin.
To validate the numerical code, single frequency waves are generated and compared with analytic solution. The arbitrary nonlinear waves can be generated by superposition of single frequency wave.
