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Aeromechanics of membrane and rigid wings in and out of ground-effect at moderate Reynolds numbers

Aeromechanics of membrane and rigid wings in and out of ground-effect at moderate Reynolds numbers
Aeromechanics of membrane and rigid wings in and out of ground-effect at moderate Reynolds numbers
Wind tunnel experiments are conducted using membrane wings and rigid flat-plates in ground-effect at a moderate Reynolds number of Re = 56 000 with ground clearances from 1% to 200% chord length measured from their trailing-edge. A six-axis load-cell captures time-resolved forces and moment while time-resolved stereo digital image correlation (DIC) measurements are performed to capture membrane motions. The lift and drag coefficients of the rigid wing in ground-effect follow well-established trends while the membrane wing appears to exhibit improved coefficients and efficiency (compared to the rigid wing) when in ground-effect. Proper orthogonal decomposition (POD) is applied to study the spatiotemporal structure of membrane vibrations. With increasing angles-of-attack and/or decreasing heights above ground, mode shapes of membrane deformation are dominated by large-scale fluctuations that have a smaller number of local extrema along the chord. Ground-effect induces modifications to the membrane deformation, which appear to be similar to the modifications induced by increasing angles-of-attack in free-flight. At high angles-of-attack in free-flight or at moderate angles in ground-effect, two POD modes of membrane fluctuations are found to be sufficient to capture 90% of all membrane deformations. Under these conditions, a membrane deformation with maximum camber near the trailing edge of the membrane wing is found to correlate with high lift, low drag and a nose down pitching moment. The extrema in membrane deformations and lift and drag forces occur simultaneously, while there is a time-lag between the deformation and the pitching moment.
0889-9746
318-331
Bleischwitz, Robert
461358e1-6d90-4a9d-bc11-4a68595d4b7a
de Kat, Roeland
d46a99a4-8653-4698-9ef4-46dd0c77ba5d
Ganapathisubramani, Bharath
5e69099f-2f39-4fdd-8a85-3ac906827052
Bleischwitz, Robert
461358e1-6d90-4a9d-bc11-4a68595d4b7a
de Kat, Roeland
d46a99a4-8653-4698-9ef4-46dd0c77ba5d
Ganapathisubramani, Bharath
5e69099f-2f39-4fdd-8a85-3ac906827052

Bleischwitz, Robert, de Kat, Roeland and Ganapathisubramani, Bharath (2016) Aeromechanics of membrane and rigid wings in and out of ground-effect at moderate Reynolds numbers. Journal of Fluids and Structures, 62, 318-331. (doi:10.1016/j.jfluidstructs.2016.02.005).

Record type: Article

Abstract

Wind tunnel experiments are conducted using membrane wings and rigid flat-plates in ground-effect at a moderate Reynolds number of Re = 56 000 with ground clearances from 1% to 200% chord length measured from their trailing-edge. A six-axis load-cell captures time-resolved forces and moment while time-resolved stereo digital image correlation (DIC) measurements are performed to capture membrane motions. The lift and drag coefficients of the rigid wing in ground-effect follow well-established trends while the membrane wing appears to exhibit improved coefficients and efficiency (compared to the rigid wing) when in ground-effect. Proper orthogonal decomposition (POD) is applied to study the spatiotemporal structure of membrane vibrations. With increasing angles-of-attack and/or decreasing heights above ground, mode shapes of membrane deformation are dominated by large-scale fluctuations that have a smaller number of local extrema along the chord. Ground-effect induces modifications to the membrane deformation, which appear to be similar to the modifications induced by increasing angles-of-attack in free-flight. At high angles-of-attack in free-flight or at moderate angles in ground-effect, two POD modes of membrane fluctuations are found to be sufficient to capture 90% of all membrane deformations. Under these conditions, a membrane deformation with maximum camber near the trailing edge of the membrane wing is found to correlate with high lift, low drag and a nose down pitching moment. The extrema in membrane deformations and lift and drag forces occur simultaneously, while there is a time-lag between the deformation and the pitching moment.

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Accepted/In Press date: 13 February 2016
e-pub ahead of print date: 8 March 2016
Published date: April 2016
Organisations: Aerodynamics & Flight Mechanics Group

Identifiers

Local EPrints ID: 391423
URI: https://eprints.soton.ac.uk/id/eprint/391423
ISSN: 0889-9746
PURE UUID: 4aff292c-1a2e-4329-b0a3-3b2089b5e300
ORCID for Roeland de Kat: ORCID iD orcid.org/0000-0002-6851-4409
ORCID for Bharath Ganapathisubramani: ORCID iD orcid.org/0000-0001-9817-0486

Catalogue record

Date deposited: 12 Apr 2016 11:06
Last modified: 07 Aug 2019 05:25

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