Wave interaction with a tethered buoy: SPH simulation and experimental validation

Understanding the interaction between surface waves and floating, moored structures is an important problem for the design of offshore structures. Experimental analysis has traditionally been used to study these problems, but using computational modelling could potentially reduce the number of experimental iterations required. In this paper we investigate the use of Smoothed Particle Hydrodynamics as a method for modelling these problems and thus reducing the number of experiments required. Validation data is obtained from generic experiments that contain the important features of wave-structure interaction. A moored spherical buoy oscillating both through and across a free surface, as well as interacting with an incident sinusoidal wave train are discussed and companion SPH simulations are run. We show here that SPH is capable of achieving accurate predictions of the buoy's motion when interacting with the free surface with appropriate particle resolutions. An initial transient motion was observed in the experiments as a long period oscillation of the buoy at its surge natural frequency. This transient motion was also predicted by SPH, but at reduced amplitude. Overall SPH was determined to be a good choice for modelling surface and structure interactions and we provide guidelines on appropriate particle resolution for such interactions.