Longitudinal Aerodynamics of Rapidly Pitching Fixed-Wing Micro Air Vehicles

Randall, Ryan; Shkarayev, Sergey; Abate, Gregg; Babcock, Judson

doi:10.2514/1.c031378

Cited by 7 publications

(20 citation statements)

References 12 publications

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“…The effect of the slipstream on stall-delay and wing lift has been noted by Kuhn and Draper 24 and by the present authors in previous studies. 3,4 Another interesting flow feature is observable from Figure 9. As the of the wing is increased to very high values, oncoming flow is displaced both downward and upward as it moves around the wing (as seen for J ¼ undefined, ¼ 86 ).…”

Section: Resultsmentioning

confidence: 89%

“…This study is a continuation of a previous study, 4 for which a test matrix has been published. The previous study's test matrix was selected based on free-flight data obtained using a successful fixed-wing VTOL MAV and restrictions imposed by the experimental testing system.…”

Section: Test Parameter Selectionmentioning

confidence: 83%

“…Flow-field trends are compared with force trends that were observed and presented in a previous studies. 3,4 Results of static tests Figure 1). The first column of images in Figure 9 corresponds to the no-slipstream case (n ¼ 0 and J ¼ undefined), where propellers have been removed, but the motor and its mount have been retained.…”

Section: Resultsmentioning

confidence: 99%

“…A recent study by Randall et al 4 addressed unsteady forces and moments exerted on a VTOL MAV dynamically pitching at constant rates, spanning 20 -70 . Pitching rates from À114 to þ114 per second were used, based on free-flight data presented in a study by Chu et al 5 This study found that propulsion system aerodynamics are not sensitive to pitching-rate, but wing aerodynamics are.…”

Section: Introductionmentioning

confidence: 99%

“…Pitching rates from À114 to þ114 per second were used, based on free-flight data presented in a study by Chu et al 5 This study found that propulsion system aerodynamics are not sensitive to pitching-rate, but wing aerodynamics are. For this and the previous study, 4 angle of attack during dynamic pitching is defined as the angle between the instantaneous wind tunnel flow direction and the instantaneous root chord-line of the wing. This definition allows for comparison of static and dynamic data.…”

Section: Introductionmentioning

confidence: 99%

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Visualization of vortical flows around a rapidly pitching wing and propeller

Randall

Wilson

et al. 2017

International Journal of Micro Air Vehicles

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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. No-pitching and four pitching-rates were used, along with three propulsive settings. Several observations were made during no-pitching tests. Turbulent wakes behind blades and laminar flow between them produces pulsations in the boundary layer. These pulsations alter the boundary layer from a laminar to turbulent state and back. An increase in lift and drag in the presence of a slipstream is a result of competing effects of the propulsive slipstream: (a) suppression of flow separation and increased velocity over the wing and (b) decrease of the effective angle of attack. 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, 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 leading-edge vortex. At lower nose-up pitching-rates, leading-edge vortices form at lower angles of attacks. As a slipstream strengthens, a few things occur: separation wakes diminish, separation occurs at a higher angle of attacks, and downward flow-deflection increases. Similar effects are observed for nose-up pitching, while nose-down pitching produces the opposite effects.

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Section: Resultsmentioning

confidence: 89%

Section: Test Parameter Selectionmentioning

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Visualization of vortical flows around a rapidly pitching wing and propeller

Randall

Wilson

et al. 2017

International Journal of Micro Air Vehicles

Self Cite

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The Aerodynamics and Hover Control for the X-wing VTOL MAV

Cao

Wei²,

Luan

et al. 2022

Proceedings of 2021 International Conference on Autonomous Unmanned Systems (ICAUS 2021)

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Comparison of wing–propeller interaction in tractor and pusher configuration

Chinwicharnam

Thipyopas

2016

International Journal of Micro Air Vehicles

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This research compared a tractor and a pusher configuration for a tilt-body vertical take-off and landing micro air vehicle using an experiment in a subsonic wind tunnel. All tests were conducted in the range 6-10 m/s and 6000-8000 RPM of the freestream and the propeller rotation, respectively. The wing model was a rectangular platform with an NACA 0012 airfoil and AR ¼ 1. The incidence angles varied within the range 0 -90 to cover flight configuration from cruise to hover and vice versa. Basically, the downstream of the propeller is stronger than the upstream. Thus the wing submerses in the propeller's downstream, which is the tractor configuration, and has an advantage over the other configuration by increasing the freestream velocity and decreasing the angle of attack. The results of the experiment found that the wing aerodynamics of the tractor were improved by the prop-wash effect with increases of about 1-1.13 times in the wing lift curve slope and about 0.9-1.12 times in the factor K of the drag polar curve. However, in the case of the pusher, the change was not significant. The stall angle, the maximum lift coefficient, and the drag coefficient at zero angle of the wing all increased in both the tractor and the pusher configurations due to the prop-wash effect. Moreover, after experiencing the prop-wash effect, the aerodynamic center of the tractor wing was almost at the same point.

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Longitudinal Aerodynamics of Rapidly Pitching Fixed-Wing Micro Air Vehicles

Cited by 7 publications

References 12 publications

Visualization of vortical flows around a rapidly pitching wing and propeller

Visualization of vortical flows around a rapidly pitching wing and propeller

The Aerodynamics and Hover Control for the X-wing VTOL MAV

Comparison of wing–propeller interaction in tractor and pusher configuration

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