| Objective: ||Develop and test a high frequency flow control device for use in controlling cavity flowfields. Develop novel supporting techniques to understand and verify the effect of the high frequency actuation.
|| Description: ||There exists a need in the U.S. Air Force to understand and control the flowfield in the vicinity of an open cavity (representing a weapons bay or some type of sensor aperture), due to the high acoustic levels and vibration loading produced by these geometric integrations. Flow control has been applied to the cavity-type integrations, in both experiments and numerical simulations, with some impressive preliminary results. In particular, pulsing near the cavity leading edge at relatively high frequency has shown great promise.
The only experimental device which has shown a conclusive link between high-frequency pulsing and enhanced suppression of acoustic levels is a rod-in-crossflow. This device cannot be used in studies or applications where it is desirable to vary frequency, because the operating frequency is directly proportional to the diameter of the rod, which cannot be varied independently. Pulsed air jets applied at the leading edge of the cavity have demonstrated significant suppression results in numerical simulation, but no physical actuator exists which can generate the required massflows and frequencies used in simulations. There exists a need for a real physical actuator in this problem area which can operate at relatively high frequency, and can produce a large perturbation at the same time. The possibility exits that plasma-type actuation could serve in this capacity. In addition, it is also desirable to investigate high-frequency forcing of existing devices like the rod in crossflow, for the purpose of extending its useful range of application (enhancing performance, operating at higher Mach numbers).
An additional capability sought is the generation of both surface and off-body data (temperatures, pressures, etc.) for the purpose of demonstrating both effects of the devices as well as illustrating physical mechanisms involved. To be useful for visualizing and quantifying mechanisms, these techniques would have to generate (as a minimum) instantaneous planes of data on the walls and in the surrounding flowfield. These novel techniques would also ideally respond at several kHz (current high frequency devices at 1/10 scale operate at up to 5 kHz).
The new high-frequency flow control devices and enhanced understanding of those devices developed here could help improve the state of several key areas that are currently being examined by the U.S. Air Force, over a wide range of frequencies and applications, including open-loop and closed-loop flow control, weapons separation, flow-structure interaction, and aero-optics mitigation.
|| ||PHASE I: Develop a compact, efficient high-frequency, large-perturbation flow control device effective in both subsonic and supersonic flow. Document design approach. Develop a novel technique to collect instantaneous planes of data in industrial wind tunnels. Bench test concepts.
|| || ||PHASE II: Prove the efficacy of these devices and techniques by testing at relevant conditions in a wind tunnel. Develop actuator design methodology. Elucidate the physics of the flow control device using nonintrusive flowfield and/or surface measurement techniques.
|| ||DUAL USE COMMERCIALIZATION: Military application: Applications include enhanced performance for many near term platforms, i.e., F-15, F-16, F-22, Joint Strike Fighter (JSF), unmanned combat aerial vehicle (UCAV), etc. Commercial application: Examples of potential commercial applications include commercial aircraft and general aviation.
|| References: ||
1. Stanek, M.J., “Control of High Speed Turbulent Free Shear Flows – Stabilization and Destabilization,” Keynote Lecture No. ICCES0520051003975, International Conference on Computational and Experimental Engineering and Sciences, Chennai, India, December 2005.
2. Chan, S., Zhang, X., and Gabriel, S., “The Attenuation of Cavity Tones Using Plasma Actuators,” 11th AIAA/CEAS Aeroacoustics Conference (26th AIAA Aeroacoustics Conference) AIAA-2005-2802, 2005, p. 14.
3. Samimy, M., Adamovich, I., Kim, J.-H., Webb, B., Keshav, S., and Utkin, Y., “Active Control of High Speed Jets Using Localized Arc Filament Plasma Actuators,” 2nd AIAA Flow Control Conference AIAA- 2004-2130, 2004, p. 14.
4. Jonassen, D.R., Settles, G.S., and Tronosky, M.D., “Schlieren “PIV” for Turbulent Flows”, to appear in Optics and Lasers in Engineering, Volume 44, Issues 3-4, March-April 2006, pp. 190-207.
5. Fonov, S., L. Goss, G. Jones, J. Crafton, and V. Fonov, “Identification of Pressure Measurement Systems based on Surface Stress Sensitive Films and Pressure Sensitive Paints,” 21st International Congress on Instrumentation in Aerospace Simulation Facilities, Sendai, Japan, 29 August-1 September 2005.
|Keywords: ||electrodynamics, plasma, cavity, flow control, nonintrusive measurement, high frequency|