Chemical Impulse Actuation for Aerodynamic Flow Control

Recent works on active flow control have emphasized the utility of momentum-based fluidic actuation produced by arrays of 2- or 3-D air jets through aerodynamic surfaces. Despite the demonstrated control effectiveness of these momentum-based approaches, their integration on realistic flight platforms has been hampered by the high required air flow rates and actuation power. The present investigations have sought to develop chemically-based impulsive actuation approaches which can produce high-velocity actuation jets while reducing or eliminating entirely the need for large on-board air supplies to produce actuation jets. A range of propellants is investigated for this approach with chemistries including spark-ignited gaseous combustion, electrically-controlled fuel/oxidizer gels, and catalytically-decomposed monopropellant liquids. The benchtop performance of these actuators is characterized in terms of the dynamic pressures that can be achieved within the reaction chambers, the pulse durations, the features of the resulting jets including their penetration into a transonic cross flow. The control authority of impulsive actuation is demonstrated in wind tunnel experiments over a generic wall-mounted 2-D NASA hump model in which a strong transitory attachment of this inherently separated flow is created.