Response Characteristics of a Discus Shaped Data Buoy in Nonlinear Waves

Abstract

The response characteristics of a discus data buoy under the action of nonlinear waves are investigated through an experimental set-up in a wave tank. The details of the model, instrumentation, testing conditions and the analysis of the results are presented and discussed in this paper. The nonlinear waves were generated in the wave tank such that their characteristics fall under the Cnoidal and Stokes wave theory regions. The measured wave elevation and responses of the buoy model were analyzed qualitatively through phase-portrait and, quantitatively through spectral and harmonic analysis. In addition, the effects of the nonlinear wave height, wave period and Ursell parameter, Ur , on the response characteristics of the buoy model are addressed. Using a linear Transfer Function (TF) obtained from linear waves, an attempt to estimate the nonlinear-wave spectral density from the buoy model dynamics is made and the uncertainties in such predictions are detailed.