Plasma Synthetic Jet Actuator

Plasma Synthetic Jet Actuator: From characterisation to separation flow control

van Pelt, Timo (TU Delft Aerospace Engineering; TU Delft Electrical Engineering, Mathematics and Computer Science)

Kotsonis, M. (mentor)
Zong, H. (graduation committee)

Delft University of Technology

Aerospace Engineering

2019-02-01

This project proposes a series of experiments that involve plasma synthetic jet actuators. The first experiment will perform a jet characterisation experiment that will research the effect of orifice geometry on the overall performance of the actuator. The second experiment will built upon the first experiment and will use a plasma synthetic jet array to combat leading edge separation of a NACA 0015 airfoil at Re=1.7⋅10⁵ and U∞=10 m/s and improve the overall performance of this particular airfoil. Special focus will be put in uncovering the underlying mechanics of plasma synthetic jet actuation operating in leading edge separation conditions and how performance is dependent on the actuation frequency. From the jet characterisation experiments a clear performance trend of actuator efficiency with respect to the converging cone angle (θ) is found. The optimal optimal orifice angle is expected to lie between 45º<θ<69º. These geometries experience ∼20% higher jet velocities than the baseline 'straight' orifice, which results in larger mass expulsions and an overall more efficient operation of the actuator. Additionally it is found that adding a small diverging section to the orifice improves upon the electro-mechanical efficiency of the plasma synthetic jet actuator. PIV measurements show that this is due to the increased effective orifice area which allows for higher mass flows through the orifice but also the jet velocities remained of similar order as the optimal converging geometries. The flow control experiments show that plasma synthetic jet actuators can indeed improve the performance of a NACA 0015 airfoil at Re=1.7⋅10⁵ and U∞=10 m/s. The force balance measurements show that PSJ actuation suppresses the hysteresis loop present when actuation is absent. Furthermore the angle at which maximum lift is achieved is shifted by ∼7º increasing the maximum achieved lift by ∼23%. Additionally, flow separation can be delayed by about 2º reducing the drag by about ∼40%. Furthermore, the PIV measurements show the mechanisms behind flow separation control. At moderate stall angles flow reattachment is feasible if the actuation frequency is high enough. At higher angles of attack the separation point moves upstream of the actuators and renders the array incapable to suppress flow separation. However, at these conditions the actuators are still able to influence the separation region and higher frequencies, with an optimum of F^*=1, are capable to suppress the separation area more. If the above-mentioned experiments translate to aeronautical applications plasma synthetic jets might be a game changer when it comes to demanding flight conditions. Not only is plasma synthetic jet actuation capable of diminishing the hysteresis effect it is also capable of considerably increasing the lift and decreasing the drag forces. These effects can considerably improve the safety of aircraft as the omission of hysteresis can reduce unwanted unsteady loads that advance structural fatigue and the higher lift coefficients reduce the need of high lift devices allowing them to become smaller and less complex in the future. Overall this allows aircraft to fly at more demanding flight conditions than previously feasible.

Plasma actuators
Active flow control
Aerodynamics

http://resolver.tudelft.nl/uuid:5a5627ae-63c1-459c-9a8b-cbbeb1a9625a

Student theses

master thesis

© 2019 Timo van Pelt