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Active Control of Flow over an Oscillating NACA 0012 Airfoil

Castañeda Vergara, David Armando
http://orcid.org/0000-0003-4264-9943
http://rave.ohiolink.edu/etdc/view?acc_num=osu1587420875168203

Abstract Details

2020, Doctor of Philosophy, Ohio State University, Aero/Astro Engineering.
Dynamic stall (DS) is a time-dependent flow separation and stall phenomenon that occurs due to unsteady motion of a lifting surface. When the motion is sufficiently rapid, the flow can remain attached well beyond the static stall angle of attack. The eventual stall and dynamic stall vortex formation, convection, and shedding processes introduce large unsteady aerodynamic loads (lift, drag, and moment) which are undesirable. Dynamic stall occurs in many applications, including rotorcraft, micro aerial vehicles (MAVs), and wind turbines. This phenomenon typically occurs in rotorcraft applications over the rotor at high forward flight speeds or during maneuvers with high load factors. The primary adverse characteristic of dynamic stall is the onset of high torsional and vibrational loads on the rotor due to the associated unsteady aerodynamic forces. Nanosecond Dielectric Barrier Discharge (NS-DBD) actuators are flow control devices which can excite natural instabilities in the flow. These actuators have demonstrated the ability to delay or mitigate dynamic stall. To study the effect of an NS-DBD actuator on DS, a preliminary proof-of-concept experiment was conducted. This experiment examined the control of DS over a NACA 0015 airfoil; however, the setup had significant limitations. The NS-DBD showed significant promise as a means of reducing the unsteady loads associated with dynamic stall, despite limitations of the proof-of-concept experiment. The limitations/issues with the preliminary set up were rectified by designing an upgraded experimental setup for examining dynamic stall flow control using NS-DBD plasma actuators on a NACA 0012 airfoil. The upgrade included installing a modular, vertically-mounted airfoil driven by a direct-drive servomotor in combination with a multi-axis force and torque transducer, all of which was controlled by a real-time data acquisition device. In addition, the airfoil (in the proof-of-concept experiment) imposed a high tunnel blockage when at large angles of attack. This issue was ameliorated by reducing the airfoil chord length and aspect ratio. End plates were added to prevent tip vortex formation and to reduce tunnel sidewall interference. Baseline data were obtained using the upgraded setup. Force and moment data from the load cell were acquired for all cases to obtain aerodynamic loading data. The results showed significantly lower uncertainty levels when compared with the data obtained from the previous setup due to the increased repeatability of the airfoil motion and the direct measurement of aerodynamic forces (which includes the effect of any potential flow three-dimensionality). After baseline experiments, a series of flow control tests on dynamic stall were performed using NS-DBD plasma actuator installed at the leading edge of the NACA 0012 airfoil. A combination of three chord-based Reynolds numbers (300,000, 500,000, and 700,000) with reduced frequencies from 0.025 to 0.075 was used. Two excitation schemes were used: continuous excitation (excitation at a given frequency continuously throughout multiple oscillation cycles, as typically done in the literature) and a new method: Excitation in Parts of the Oscillating Cycle (EPOC). EPOC is excitation over a selected portion of the oscillating cycle or a variation of the excitation in the oscillation cycle. From load cell and PIV results, it is concluded that continuous excitation for deep and light stall produces significant changes in lift, drag, and moment during the oscillating cycle. Excited cases exhibit a reduction in lift hysteresis, peak drag, and negative damping compared with baseline due to the effects of excitation-triggered coherent structures. Results for light and deep dynamic stall using EPOC control showed that it is possible to improve a particular benefit (e.g. reduction in lift hysteresis, negative damping or drag) with targeted control and the use of a particular excitation timing during the oscillating cycle. Different EPOC schemes can be used for different situations depending on the application requirements.
Mo Samimy (Advisor)
Datta Gaitonde (Committee Member)
Jim Gregory (Committee Member)
Miguel Visbal (Committee Member)
Webb Nathan (Committee Member)
Le Huyen (Other)
223 p.
Aerospace Engineering
Unsteady Aerodynamics, Flow Control, Plasma actuator, Dynamic Stall

Recommended Citations

Citations

  • Castañeda Vergara, D. A. (2020). Active Control of Flow over an Oscillating NACA 0012 Airfoil [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587420875168203

    APA Style (7th edition)

  • Castañeda Vergara, David. Active Control of Flow over an Oscillating NACA 0012 Airfoil. 2020. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1587420875168203.

    MLA Style (8th edition)

  • Castañeda Vergara, David. "Active Control of Flow over an Oscillating NACA 0012 Airfoil." Doctoral dissertation, Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587420875168203

    Chicago Manual of Style (17th edition)

osu1587420875168203
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© 2020, some rights reserved.Creative Commons License Active Control of Flow over an Oscillating NACA 0012 Airfoil by David Armando Castañeda Vergara is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by The Ohio State University and OhioLINK.