Aerodynamic performance and robustness of a nature-inspired concept for a microscale wind turbine

Abstract

We present direct numerical simulations of a novel concept for a microscale wind turbine, inspired in the mechanics of the autorotation of winged seeds. In this nature-inspired concept, the turbine blades have two degrees of freedom: the pitch and the elevation (or coning) angles. These allow the blade to vary its attitude with respect to the incoming velocity seen by the blade (i.e., the tip-speed ratio, λ). In order to validate this new concept, we perform numerical simulations of the coupled fluid–solid problem, solving together the Navier–Stokes equations for the fluid and the Newton equations for the rigid body (i.e., the blade). We characterize a preliminary nature-inspired single-blade rotor over a range of operational conditions (including both uniform and turbulent inflows), demonstrating the ability of the novel rotor to extract power at a very low Reynolds number (i.e., Re=240 based on the blade’s chord and the freestream velocity), significantly changing its attitude in response to different braking torques and tip-speed ratios. The rotor achieves a peak power coefficient of CP,max=0.026 at λ≈2.0. This peak value is unchanged between uniform and turbulence-perturbed inflows, demonstrating the robustness of the nature-inspired design. However, performance remains lower than that of fixed-blade configurations, showing that while the concept is feasible and stable, optimization of blade planform and mass distribution is essential to improve efficiency.