Development of a free vortex wake method code for offshore floating wind turbines

Offshore floating wind turbines (OFWTs) present unique aerodynamic analysis challenges. Motion–derived velocity perturbations in the wake necessitate higher–fidelity aerodynamic analysis methods than the ubiquitous momentum balance techniques currently in use. A more physically–sound approach is to model the wake generated by a wind turbine rotor as a freely convecting lattice, using the resultant inflow to estimate rotor loads, as it done with a free vortex wake method (FVM). The FVM code Wake Induced Dynamics Simulator (WInDS) was developed at the University of Massachusetts at Amherst to predict the aerodynamic loading and wake evolution of an OFWT to a higher degree of accuracy than is possible via momentum balance methods. A series of validation cases were conducted to provide some basis for applying WInDS to floating wind turbine cases, for which no aerodynamic experimental data is currently available. The results from these tests show that WInDS is able to accurately predict the aerodynamically–derived loads and wake structures generated by various fixed and rotary–wing cases, and may therefore be applied to more complex cases, like OFWTs, with a degree of confidence.