Numerical Investigation of Dynamic Inflow Effect on Unsteady Aerodynamic Loading and Broadband Noise of Horizontal Axis Wind Turbines

Abstract

Horizontal axis wind turbines (HAWTs) are subjected to complex environmental effects such as atmospheric turbulence, wind shear and inertial translational and rotational motion of support platform. Thus, it is debatable whether the aerodynamic load predictions of an HAWT using the conventional blade element momentum (BEM) theory, which does not consider the dynamic wake effects, are accurate. Although a generalized dynamic wake (GDW) method has been developed to consider the dynamic inflow effect, it is only stable for lightly loaded at high wind speeds. In contrast to the BEM and GDW, the unsteady vortex lattice method (UVLM) can inherently represent the non-uniform flow effects of the trailing wake from the turbine blades. In this work, a fully coupled dynamics model has been developed and extensively validated against results of wind tunnel test and a field experiment. Then, the wake influence of offshore floating wind turbines (OFWTs) at low wind-speed conditions was investigated by comparing three wake models: the BEM, GDW, and UVLM. The OC3-Hywind model was chosen for OFWT simulation. Result shows that the blade flapwise bending moment, rotor torque, and tower side-to-side bending moment were underestimated without considering dynamic inflow at low wind speeds. Also, aeroacoustic noise prediction of HAWTs was performed using semi-empirical formula. It was investigated in a low-wind speed condition to figure out the effect of dynamic inflow on flow-induced noise generation. Result shows that turbulent ingestion and trailing edge bluntness noise was not changed significantly. However, trailing edge noise increases in level due to lower prediction of induced velocity when considering the dynamic inflow.