Multiple actuators flow control over a Glauert-Goldschmied type airfoil at low Reynolds numbers

Thick airfoils are desirable for optimized structure, large volume, lower weight and more. Low Reynolds numbers flight of Miniature Aerial Vehicles (MAV) is complex, with thick boundary layers and laminar separations. However, the slow flight requires lower thrust, therefore the applicability of active flow control methods due to the significant control authority that zero-net-mass-flux actuators can exert on the flow become appealing. Active flow control can modify the flow as required to perform all functions to sustain and to control flight at low Reynolds numbers. An experiment on a modified Glauert-Goldschmied type airfoil, with a thickness ratio of 20% and Zeronet- mass-flux Piezo-electric fluidic actuators located at the leading and trailing edges of the airfoil was performed at low Reynolds numbers. At high angles of attack (>20°) the leading edge actuators, using very low momentum pulsed modulation input, were able to reattach the flow. Delay of stall and significant increase of C_l,max was achieved. Using the trailing edge actuators with higher momentum coefficients and high frequency pure sine wave excitation enabled both reduction of C_d at all angles of attack and increasing of C_l at low angles of attack (<14°). Significant control of pitching moment was also demonstrated. Combination of the two actuator placements allows efficient combination of the control authority that was found for each actuator operating alone.