Validation of a Partially Nonlinear Time Domain Model using instantaneous Froude-Krylov and Hydrostatic Forces

The aim of this study is to validate and assess the capability of an advanced hydrodynamic time-domain model through the comparison of numerical and experimental results of a small-scale bottom-fixed pitch buoy wave energy converter. The series of tests have been conducted in the hydraulic laboratory of Aalborg University. The device is a prototype of a singleWavestar float, scaled at 1:20, considering one degree of freedom only. The tests included a various range of incoming waves, from small regular waves to storm conditions irregular waves.The numerical simulations have been performed at the WavEC using an in-house time-domain model. The code, based on the linear potential theory, solves the system of motion equations using state-space representations of the radiation terms and includes nonlinear hydrostatic forces and nonlinear Froude-Krylov excitation terms, which require the instantaneous detection of the floating body wetted surface. The idea behind this approach is first to increase the model accuracy (compared to the fully linear model method), but also to keep the computational time relatively low.Results show a good agreement between experimental and numerical data, which enhance significantly the confidence in using such sort of models to simulate the behavior of wave energy converters