Effect of Airfoil Wall Temperature on the Performance of Micro-Rotorcraft

The improvement of aerodynamic efficiency of small-scale airfoils using surface temperature and heat transfer is investigated using numerical simulations and experimental work. The basic idea is to take a direct advantage of heat transfer that dominates micro-scale systems to enhance lift, reduce drag, and increase the envelope of operation of airfoils. It is shown that while varying wall temperature does not produce significant impact at the full-scale (Reynolds numbers > 106), since the thickness of the thermal boundary layer is very small compared to the airfoil chord and the viscous boundary layer, its effect is very pronounced at the micro-scale. The numerical simulation demonstrates that most of the effect actually comes from the heat transfer in the much smaller nose region of the small-scale airfoil. Experimental results show good agreement with numerical simulations.