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MS_Thesis_2018_Mark_Sutkowy.pdf (10.71 MB)

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Relationship between Rotor Wake Structures and Performance Characteristics over a Range of Low-Reynolds Number Conditions

Sutkowy, Mark Louis, Jr.
http://orcid.org/0000-0003-4912-391X
http://rave.ohiolink.edu/etdc/view?acc_num=osu1534768619864476

Abstract Details

2018, Master of Science, Ohio State University, Aero/Astro Engineering.
Small-scale rotors exhibit degraded aerodynamic efficiency, which has been linked to non-ideal losses within their wake. Many small unmanned aircraft systems (UAS) are powered by such rotors, and are currently at the forefront of aerospace research for a multitude of innovative applications. As such, a comprehensive understanding of their operational capabilities is critical for implementation in the field. A great deal of attention has been given to characterize the performance of large-scale rotor models. However, similar studies for small-scale, low Reynolds number (Re) applications has received relatively little attention. This work seeks to gather insight into the behavior of the rotor wake structures as a function of Re, relate this to performance capabilities and the corresponding far-field acoustic signature. Two-component particle image velocimetry (PIV), performance, and acoustic measurements were performed using three small-scale, NACA 0012 rotors operated over a range of low-Reynolds number conditions. Rotor geometry and operational speed (Ω) were varied to obtain the desired Re variation. Spanwise PIV has demonstrated an absence of tip vortex formation as the operational thrust coefficient (CT) is increased, suggesting the presence of outboard tip stalling. Phase-locked, chordwise PIV has confirmed this hypothesis, showing the development of flow separation and a highly turbulent downstream wake. Thrust and torque measurements show degraded rotor performance at the onset of these conditions, especially at low Re. A vortex identification scheme was used to locate downstream tip vortices and characterize their size, swirl velocity, and aperiodic wandering behavior for different operational conditions. When observed at constant wake age, the wandering motion of the vortices behaved independently of vortex Reynolds number (Rev) scaling. The normalized standard deviation of the tip vortex wander was found to match well with historically observed trends, but a difference in magnitude suggests aperiodicity depends strongly on blade number instead. Chordwise PIV measurements revealed the wake characteristics at moderate collective angles (θ) produce periodic counter-rotating structures which are attributed to laminar boundary layer vortex-shedding. Acoustic measurements at similar operating conditions show significant broad-band, high frequency peaks. The broad-band peaks were found to correlate well with a physical quantification of the shedding phenomenon.
James Gregory, Ph.D (Advisor)
Jeffrey Bons, Ph.D (Committee Member)
Matthew McCrink, Ph.D (Committee Member)
143 p.
Aerospace Engineering
Rotorcraft Aerodynamics; Low-Reynolds Number Rotors; Rotor Wake Structures; Rotor Performance; UAV Aerodynamic Efficiency

Recommended Citations

Citations

  • Sutkowy, Jr., M. L. (2018). Relationship between Rotor Wake Structures and Performance Characteristics over a Range of Low-Reynolds Number Conditions [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534768619864476

    APA Style (7th edition)

  • Sutkowy, Jr., Mark. Relationship between Rotor Wake Structures and Performance Characteristics over a Range of Low-Reynolds Number Conditions. 2018. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1534768619864476.

    MLA Style (8th edition)

  • Sutkowy, Jr., Mark. "Relationship between Rotor Wake Structures and Performance Characteristics over a Range of Low-Reynolds Number Conditions." Master's thesis, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534768619864476

    Chicago Manual of Style (17th edition)

osu1534768619864476
977
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This open access ETD is published by The Ohio State University and OhioLINK.