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High-Frequency, Resonance-Enhanced Microactuators with Active Structures for High-Speed Flow Control

Title: High-Frequency, Resonance-Enhanced Microactuators with Active Structures for High-Speed Flow Control.
Name(s): Kreth, Phillip Andrew, author
Alvi, Farrukh S., professor directing dissertation
Locke, Bruce R., university representative
Shih, Chiang, committee member
Oates, William S., committee member
Florida State University, degree granting institution
College of Engineering, degree granting college
Department of Mechanical Engineering, degree granting department
Type of Resource: text
Genre: Text
Issuance: monographic
Date Issued: 2015
Publisher: Florida State University
Place of Publication: Tallahassee, Florida
Physical Form: computer
online resource
Extent: 1 online resource (236 pages)
Language(s): English
Abstract/Description: The need for actuators that are adaptable for use in a wide array of applications has been the motivation behind actuator development research over the past few years. Recent developments at the Advanced Aero-Propulsion Laboratory (AAPL) at Florida State University have produced a microactuator that uses the unsteadiness of a small-scale impinging jet to produce pulsed, supersonic microjets - this is referred to as the Resonance-Enhanced Microjet (REM) actuator. Prior studies on these actuators at AAPL have been been somewhat limited in that the actuator response has only been characterized through pressure/acoustic measurements and qualitative flow visualizations. Highly-magnified particle image velocimetry (PIV) measurements were performed to measure the velocity fields of both a 1 mm underexpanded jet and an REM actuator. The results demonstrate that this type of microactuator is capable of producing pulsed, supersonic microjets that have velocities of approximately 400 m/s that are sustained for significant portions of their cycles (> 60 %). These are the first direct velocity measurements of these flowfields, and they allow for a greater understanding of the flow physics associated with this microactuator. The previous studies on the REM actuators have shown that the microactuator volume is among the principal parameters in determining the actuator's maximum-amplitude frequency component. In order to use this actuator in a closed-loop, feedback control system, a modified design that incorporates smart materials is studied. The smart materials (specifically piezoelectric ceramic stack actuators) have been implemented into the microactuator to actively change its geometry, thus permitting controllable changes in the microactuator's resonant frequency. The distinct feature of this design is that the smart materials are not used to produce the primary perturbation or flow from the actuator (which has in the past limited the control authority of other designs) but to change its dynamic properties. Various static and dynamic control inputs to the piezo-stacks illustrate that the actuator's resonant frequency can be modulated by a few hundred Hertz at very fast rates (up to 1 kHz or more). These frequency modulation capabilities allow for off-design frequencies to be present in the actuator's output, thereby increasing its range of potential flow control applications. A series of closed-loop control demonstrations clearly show the ability of this actuator to track and produce outputs at specified frequencies. The robustness of this control technique was also demonstrated. By combining the REM actuator concept with the precision and control authority of smart materials, the new actuator system (known as the SmartREM actuator) is shown to produce supersonic, pulsing microjets whose frequency can be controlled actively in a closed-loop manner. Three different design possibilities are developed and characterized in this study. An optimal configuration was identified for cavity flow control experiments in both sub- and supersonic freestream conditions (M = 0.4 - 0.7 and M = 1.5). The actuator was designed such that its frequency would lie within the range of the predicted cavity oscillations. The actuator's performance was evaluated in its three modes of operations: pulsed (REM mode), active pulsed (SmartREM mode), and steady. It was found that when the actuator operates in its pulsed modes, the amplitude of the dominant peak is reduced by as much as 6 dB. The high-frequency broadband levels and overall sound pressure levels (OASPLs) are reduced with control as well (by about 3 dB). Operating the actuator in its steady mode at very high pressures provides the most effective results. The dominant peaks were completely eliminated (amplitudes reduced by over 25 dB), and the reductions in the OASPLs exceeded 10 dB.
Identifier: FSU_migr_etd-9635 (IID)
Submitted Note: A Dissertation submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy.
Degree Awarded: Summer Semester 2015.
Date of Defense: June 30, 2015.
Keywords: Actuators, Cavity Flow, Flow Control
Bibliography Note: Includes bibliographical references.
Advisory Committee: Farrukh Alvi, Professor Directing Dissertation; Bruce Locke, University Representative; Chiang Shih, Committee Member; William Oates, Committee Member.
Subject(s): Mechanical engineering
Aerospace engineering
Persistent Link to This Record:
Owner Institution: FSU

Choose the citation style.
Kreth, P. A. (2015). High-Frequency, Resonance-Enhanced Microactuators with Active Structures for High-Speed Flow Control. Retrieved from