Numerical analysis of pitching-rotor aerodynamics

Abstract

The influence of periodic blade pitching on rotor aerodynamics is numerically investigated at a Reynolds number typical of micro-air vehicles. Blade pitching motion is parameterized using three variables, giving rise to a large parameter space that is explored through 74 test cases. Results show that a relevant tuning of pitching variables can lead to an increase in rotational efficiency and thrust, which is found to be primarily related to the occurrence of reversed von Karman street, leading edge vortex (LEV) formation and dynamic stall phenomenon. In addition, for cases where reversed von Karman street occurs, the flow is found to be quasi-two-dimensional, suggesting that quasi-twodimensional approaches can provide relevant approximations of the global aerodynamics. Overall, the analysis demonstrates that blade pitching can be beneficial to the aerodynamic performance of micro-air vehicles and helps draw guidelines for further improvements of flapping-rotor concepts.

Prediction of Noise from Low Reynolds Number Rotors with Different Number of Blades using a Non-Linear Vortex Lattice Method

“…Overall, it is shown that NVLM predicts thrust within 6% of experimental values. This level of accuracy is in line with previous works on low Reynolds number rotors [14][15][16]. Note that results obtained from NVLM depend on aerodynamic polars used as input for the look-up table procedure.…”

Fluid–Structure Interactions and Unsteady Kinematics of a Low-Reynolds-Number Rotor

“…Overall, these studies suggested that thrust could significantly be enhanced with respect to conventional rotors yet with lower efficiency. Similar conclusions were raised for a pitching rotor [13], where the rotating blade undergoes a pitching motion about a spanwise axis (without flapping motion). In a general manner, the research on improved kinematics is a potential way to increase the performance of propulsive systems [14].…”

Aerodynamic Performance of a Hovering Microrotor in Confined Environment

“…Recent numerical results on a similar geometry (Ref. 24) show that in this case, the flow separates at the leading edge and rolls up into a recirculation bubble (or leading edge vortex) that remains attached to the upper surface of the blade, thereby increasing the virtual camber of the blade profile. In addition, it is worth mentioning that blade element momentum theory predicts local effective incidences along the blade span lower than 10 • for all rpm tested in this paper.…”