Remotely operated aerial vehicles such as quadcopters and drones have been, and continue to be, used extensively by military personnel, industry, and civilians alike. Current research into unsteady flapping mechanisms has been primarily concerned with the heaving and pitching motion of rigid foils. The purpose of this thesis is to investigate how a dynamically morphing foil affects the fluid-structure interactions of unsteady flapping locomotion as measured by lift, drag, and vorticity. The effects of non-dimensional heaving amplitude and reduced frequency are studied using force sensor and Particle Image Velocimetry (PIV) measurements. Two reduced frequencies are tested: one in the unsteady range, κ=0.105, and one in the highly unsteady range, κ=0.209. Two morphing modes were investigated: spanwise twisting in the direction of upward pitch (Mode A), and spanwise twisting in the direction of downward pitch (Mode B). The effects of changing reduced frequency and nondimensional heaving amplitude were explored for each morphing mode. Force sensor measurements showed that Mode A recovered some of the lift that is usually lost during the upstroke of flapping locomotion. Additionally, Mode A maintained a near-constant lift coefficient during the transition between downstroke and upstroke, suggesting a more stable form of locomotion. PIV results showed that Mode A limits circulation and leading-edge vortex (LEV) growth during the downstroke, keeping Cd ≈ 0 at the cost of reduced lift. By contrast, PIV results showed that Mode B increases the circulation during the downstroke, resulting in large increases in both lift and drag coefficients. Force sensor data showed that this effect on lift is reversed during the upstroke, where Mode B causes negative lift. The effects of each morphing mode is caused by changes in shear layer velocity that occur as a result of spanwise twisting. The twisting performed by Mode A reduces the effective angle of attack, resulting in a reduced shear layer velocity and lower circulation. The twisting performed by Mode B does the exact opposite, increasing the effective angle of attack and consequently increasing the shear layer velocity and circulation.
| Identifer | oai:union.ndltd.org:ucf.edu/oai:stars.library.ucf.edu:etd2020-2158 |
| Date | 01 January 2021 |
| Creators | Soto, Carlos |
| Publisher | STARS |
| Source Sets | University of Central Florida |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Electronic Theses and Dissertations, 2020- |
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