Hover Performance of Rotor Blades at Low Reynolds Numbers for Rotary Wing Micro Air Vehicles. An Experimental and CFD Study

An e‐cient small-scale hovering rotor is required to make a rotary-wing micro air vehicle conflguration practical. Experimental studies show that for a variety of rotors at low Reynolds numbers (Re<50,000), poor performance was consistently measured. Figure of merit was determined experimentally, and surface ∞ow visualization was implemented on the rotor blades with the use of ∞uorescent oil. A Blade Element Momentum Theory model of the rotor was used to examine the rotor performance, providing spanwise lift distribution and two dimensional airfoil characteristics. CFD models of the tested rotors were implemented and the results were compared to the BEMT and experimental results. Although the CFD results have a good qualitative agreement with experiments, an overprediction of the flgure of merit between 10% and 20% was obtained in the CFD simulation. This result was consistent with the CFD ∞ow visualization, which predicts a larger region of attached ∞ow than observed experimentally. More work is needed to determine how much of the difierence in results is due to geometric issues as opposed to CFD modeling inadequacies.