Computational and experimental studies of asymmetric pitch/plunge flapping - The secret of biological flyers

Chasman, Daniel; Chakravarthy, Sukumar

doi:10.2514/6.2001-859

Cited by 3 publications

(1 citation statement)

References 9 publications

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“…The smoke-wire was installed perpendicular to the wing and the flow direction, and was located 2.51C (C: mean chord length of the hind-wing) from the wing tip of the fore-wing and 0.59C from the leading edge of the fore-wing. The range of the reduced frequency was determined based on Chasman and Chakravarthy (2001), who used a dragonfly model seven-times larger in size than a real dragonfly and chose wing beat frequencies of 0.57, 1.00 and 1.59, which match the beat frequencies of real dragonflies, in order to achieve dynamic similarity. The wing beat frequencies in the present study were determined as 0.96 and 1.43, which correspond to the reduced frequencies of K = 0.150 and 0.225, respectively.…”

Section: Experimental Set-up and Proceduresmentioning

confidence: 99%

Flow visualization and aerodynamic-force measurement of a dragonfly-type model

Kim

Chang

Sohn

2008

J Vis

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An unsteady flow visualization and force measurement were carried out in order to investigate the effects of the reduced frequency of a dragonfly-type model. The flow visualization of the wing wake region was conducted by using a smoke-wire technique. An electronic device was mounted below the test section in order to find the exact position angle of the wing for the visualization. A load-cell was employed in measuring aerodynamic forces generated by a plunging motion of the experimental model. To find the period of the flapping motion in real time, trigger signals were also collected by passing laser beam signals through the gear hole. Experimental conditions were as follows: the incidence angles of the foreand hind-wing were 0° and 10°, respectively, and the reduced frequencies were 0.150 and 0.225. The freestream velocities of the flow visualization and force measurement were 1.0 and 1.6m/sec, respectively, which correspond to Reynolds numbers of 3.4 × 10 3 and 2.9 × 10 3 . The variations of the flow patterns and phase-averaged lift and the thrust coefficients during one cycle of the wing motion were presented. Results showed that the reduced frequency was closely related to the flow pattern that determined flight efficiency, and the maximum lift coefficient and lift coefficient per unit of time increased with reduced frequency.

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Section: Experimental Set-up and Proceduresmentioning

confidence: 99%

Flow visualization and aerodynamic-force measurement of a dragonfly-type model

Kim

Chang

Sohn

2008

J Vis

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Membrane wing aerodynamics for micro air vehicles

Lian

Shyy

Viieru

et al. 2003

Progress in Aerospace Sciences

181

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Membrane Wing-Based Micro Air Vehicles

Shyy

Ifju

Viieru

2005

Applied Mechanics Reviews

129

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Micro air vehicles (MAVs) with a wingspan of 15cm or shorter, and flight speed around 10m∕s have attracted substantial interest in recent years. There are several prominent features of MAV flight: (i) low Reynolds number (104-105), resulting in degraded aerodynamic performance, (ii) small physical dimensions, resulting in certain favorable scaling characteristics including structural strength, reduced stall speed, and impact tolerance, and (iii) low flight speed, resulting in order one effect of the flight environment and intrinsically unsteady flight characteristics. Flexible wings utilizing membrane materials are employed by natural flyers such as bats and insects. Compared to a rigid wing, a membrane wing can better adapt to the stall and has the potential for morphing to achieve enhanced agility and storage consideration. We will discuss the aerodynamics of both rigid and membrane wings under the MAV flight condition. To understand membrane wing performance, the fluid and structure interaction is of critical importance. Flow structures associated with the low Reynolds number and low aspect ratio wing, such as pressure distribution, separation bubble, and tip vortex, as well as structural dynamics in response to the surrounding flow field are discussed. Based on the computational capabilities for treating moving boundary problems, an automated wing shape optimization technique is also developed. Salient features of the flexible-wing-based MAV, including the vehicle concept, flexible wing design, novel fabrication methods, aerodynamic assessment, and flight data analysis are highlighted.

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Computational and experimental studies of asymmetric pitch/plunge flapping - The secret of biological flyers

Cited by 3 publications

References 9 publications

Flow visualization and aerodynamic-force measurement of a dragonfly-type model

Flow visualization and aerodynamic-force measurement of a dragonfly-type model

Membrane wing aerodynamics for micro air vehicles

Membrane Wing-Based Micro Air Vehicles

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