The oscillatory suction actuator: Fundamentals, interactions and efficiency

An experimental study of a new oscillatory suction actuator with no moving parts was conducted, for active flow control applications. Following the SaOB (Steady Suction and Oscillatory Blowing) actuator, a new actuator was developed with the ability to create both oscillatory suction and oscillatory blowing. The investigation was conducted in three steps – a benchtop characterization in still-air, actuation-transitional boundary layer interaction over a flat-plate in a small-scale low-speed wind tunnel and implementation on a specially designed airfoil which was tested in a medium-scale wind tunnel. The actuator concept is based on pulsing a pair of ejectors by a single fluidic oscillator. The results show an increase in the actuation efficiency in comparison to steady suction, resulting from a lower energy consumption that leads to the same desired airfoil performance. Lower values of momentum thickness, θ, (points on the ability to delay boundary layer separation) are also achieved by the unsteady suction in comparison to the steady suction.