Active control of flows for a wide array of applications has seen a surge of activity in recent years due to the potentially substantial gains in performance offered by flow control schemes. For example, control or delay of flow separation over airfoils and lifting bodies can significantly extend the operating envelope of aircraft by improving their aerodynamic performance. The control of aeroacoustically induced flow oscillations in cavity flows is another area where various active (and passive) control methods are being explored. Flows where control can be applied are wide and varied with more applications are likely to appear as the technology matures.
Efficient control of flows requires the use of effective actuators, which can be adapted for specific applications. The proposed invention describes the design and development of pulsed actuator systems capable of producing high bandwidth, high momentum microjet arrays for active flow and noise control applications. Our results clearly show that the present design produces microjets with a very high mean momentum (high subsonic to supersonic) as well as a very significant unsteady component. Studies have been conducted over a large range of actuator and flow parameters, in terms of cavity length, source jet NPR and source jet impingement distance.
The results unequivocally demonstrate the ability to vary the frequency as well as the amplitude of the mean and unsteady momentum of the microjets issuing from this actuator. By varying the dimensions of the actuator by only few hundred microns one can tune the frequency of the unsteady component from the order of a 100 Hz to 100 kHz, or more if needed. The ability to produce unsteady flow with significant mean and unsteady components, where the dynamic range can be easily varied makes these actuators promising for a number of subsonic and supersonic flow control applications for both internal and external flows.
