Abstract
This study was conducted to visually investigate flows related to fixed-wing vertical-takeoff-and-landing micro air vehicles, using the smoke-wire technique. In particular, the study examines transition between forward flight and near-hover. The experimental model consists of a rigid Zimmerman wing and a propulsion system with contra-rotating propellers arranged in a tractor configuration. The model was pitched about the wing's aerodynamic center at approximately constant rates using a five-axis robotic arm. Constant-rate pitching angles spanned 20 to 70 degrees. Five pitching-rates were used, along with three propulsive settings. Several observations were made. Contra-rotating slipstreams generally cause a delay in the onset of trailing-edge vortex-shedding within their vicinities. Higher nose-up pitching-rates generally lead to greater trailing-edge vortex-shedding frequency. Nose-up pitching without a slipstream can lead to the development of a traditional dynamic-stall leading-edge vortex (LEV), delaying stall and increasing wing lift. During nose-up pitching a slipstream can drive periodically-shed leading-edge vortices into a larger vortical-structure that circulates over the upper-surface of a wing in a fashion similar to that of a traditional dynamic-stall LEV. At lower nose-up pitching-rates LEVs form at lower angle of attack. As a slipstream strengthens a few things occur: separation wakes diminish, separation occurs at a higher AOA and downward flow-deflection increases. Similar effects are observed for nose-up pitching, while nose-down pitching produces the opposite effects.
Original language | English (US) |
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DOIs | |
State | Published - 2012 |
Event | 50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition - Nashville, TN, United States Duration: Jan 9 2012 → Jan 12 2012 |
Other
Other | 50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition |
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Country/Territory | United States |
City | Nashville, TN |
Period | 1/9/12 → 1/12/12 |
ASJC Scopus subject areas
- Aerospace Engineering