Session: New & Innovative Floating Designs I

Paper Number: 97410

97410 - Numerical Investigation of the Wave Following Hypothesis for a Shallow Draft Floating Wind Turbine 

The global offshore wind resource is vast, but much of it requires floating wind turbines of lower cost to harvest economically. A design with shallow draft and large waterline area relative to its weight has advantages such as low system weight, deployability from shallow ports, low wave loading, and easy towability. However, such turbines will also have significant wave-induced motions and corresponding inertial loading of the rotor nacelle assembly. A simple idealization for the behavior of such a system is that each float perfectly follows its local water level elevation and surge, except as dictated by rigid-body consistency. While this idealization can provide convenient estimates of motions and inertial loading that are useful for design, the validity of the underlying assumptions has not yet been scrutinized. To better understand these assumptions, this paper uses ANSYS AQWA to numerically investigate the two-dimensional behavior of a two-float shallow-draft wind turbine subjected to regular and irregular waves, mooring force-displacement relations, and float shape. Results are presented in terms of Response Amplitude Operators (RAOs) and nonlinear time histories of surge, heave and pitch – of individual floats as well as the entire system. The results show that when the float shape and mooring system are designed to encourage wave-following, the float-system midpoint approximately follows the mean surge and heave of the floats, while system pitch is affected by hydrostatic compliance in reacting moments arising from surge and surface slope.

Presenting Author: Raditya Danu Riyanto Northeastern University