Unsteady vortex lattice method coupled with a linear aeroelastic model for horizontal axis wind turbine

Many aerodynamic phenomena on wind turbines are extremely complicated, such as the ground boundary layer effects, directional and spatial variations in wind shear, unsteady yaw effects, and unsteady aerodynamics due to the platform motion of offshore floating wind turbines. Thus, it is unclear whether prediction of the aerodynamic load of a turbine using conventional blade element momentum theory is accurate. On the other hand, this method does not consider unsteady wake effect behind the rotor, the unsteady vortex lattice method can treat non-uniform flow effects derived from the trailing wake from the turbine. Moreover, the aeroelasticity of wind turbines is significant because of the recent scaling up of the turbine size. This induces unsteady aerodynamic phenomena because of fluctuations in the geometrical relative velocity and induced velocity. In the present work, we developed a fully coupled simulation code and analyzed the unsteady aerodynamics of wind turbines by substituting aerodynamic model from FAST's AeroDyn to the vortex lattice method. The developed code was validated with unsteady aerodynamic experimental Phase VI data from the National Renewable Energy Laboratory. Finally, the results show that the developed coupled code yields accurate values and good performance in the unsteady yaw case.