Study of a small scale rotor in propulsive and energy harvesting conditions

Abstract

The present manuscript investigates the aerodynamic performance of a small-scale rotor for drone applications using the Detached-Eddy Simulation method. Particular attention is devoted to the hovering and advancing flight regimes, where the flow is dominated by strong vortex structures, wake unsteadiness, and elevated turbulence intensity. The simulation results were validated against experimental data through a dual approach: thrust coefficients were measured in hovering conditions in air, while wake flow fields were characterized using particle image velocimetry in water, leveraging fluid dynamic similarity. Comparisons included instantaneous velocity, vorticity, Q-criterion, and the double divergence of the Lighthill tensor in the wake. This combined validation strategy provided a robust assessment of the numerical predictions. The analysis was subsequently extended to various operating conditions, including hovering and forward flight, in order to examine velocity fields and apply vortex identification criteria for a detailed characterization of the formation and evolution of key turbulent structures in the wake. An interesting result emerges in the advancing condition, where the results reveal the possibility of energy harvesting from the wake. This effect, observed as a local extraction of energy, is particularly relevant in the context of drones, where onboard energy recovery can contribute to improved endurance and operational efficiency.

Keywords: CFD, energy harvesting, small scale rotor, overset, drone, hpc