Physical model studies on discus buoy in regular, random and double peak spectral waves

An experimental investigation was carried out to study the motion characteristics of a data buoy under regular as well as uni-modal and bimodal sea states. For the present study, the 2.2 m diameter discus shaped data buoy of India's National Data Buoy Programme (NDBP) was scale modeled and, its heave and pitch motions were measured by two methods using potentiometers and motion capturing non contact infra-red cameras. The response amplitude operators obtained through the present experiment are proved to be predicting the different ranges of sea states well. The details of the model, instrumentation, testing conditions and the response amplitude operators for heave and pitch as a function of excitation frequency are presented and discussed in this paper.