The advance ratio effect on the lift augmentations of an insect-like flapping wing in forward flight

Cited 30 time in webofscience Cited 0 time in scopus
  • Hit : 436
  • Download : 0
Time-varying force/moment measurements and digital particle image velocimetry (DPIV) were conducted to reveal the influence of an advance ratio J on an insect-like flapping wing. A scaled-up robotic model and a servo-driven towing tank were employed to investigate nine individual J cases -J = 0 (hovering), 0.0625, 0.1250, 0.1875, 0.25, 0.50, 0.75, 1.0 and infinity (gliding motion) - at a high Reynolds number (Re similar to 10(4)). At J <= 0.25, the aerodynamic forces slightly increased from those in hover (J = 0). The centres of pressure in these cases were concentrated in the outboard section, and the leading-edge vortices (LEVs) grew more conically than those in hover. Spanwise cross-sectional DPIV indicated that the wings generated more balanced downwashes, which effectively supported the slight lift increments in this range. At J > 0.25, a drastic force drop appeared as J increased. The DPIV results in the J = 0.5 case clearly showed a strong trailing-edge vortex on the outboard trailing edges encroaching into the upper surface, which had been occupied by the LEV for lower J. The LEV vorticity was noticeably weakened, and coherent substructures with substantial turbulence accompanied this vorticity. In the J = 1.0 case, such encroachment was extended to 50% of the section, and the LEV outboard became significantly irregular. The near-wake structures also showed that the J = 1.0 case had the narrowest downwash area, with unstable root and tip vortices, which reflected considerable attenuation in the lift enhancements. It was of note that all of these vortical behaviours were clearly distinguishable from aspect ratio (AR) effects. The J even played a similar role to that of the AR in the Navier-Stokes equation. These findings clearly indicated that the J could be an independent quantity governing the overall vortical system and lift enhancing mechanism on a flapping wing of a flapping-wing micro air vehicle
Publisher
CAMBRIDGE UNIV PRESS
Issue Date
2016-12
Language
English
Article Type
Article
Citation

JOURNAL OF FLUID MECHANICS, v.808, pp.485 - 510

ISSN
0022-1120
DOI
10.1017/jfm.2016.629
URI
http://hdl.handle.net/10203/214809
Appears in Collection
AE-Journal Papers(저널논문)
Files in This Item
There are no files associated with this item.
This item is cited by other documents in WoS
⊙ Detail Information in WoSⓡ Click to see webofscience_button
⊙ Cited 30 items in WoS Click to see citing articles in records_button

qr_code

  • mendeley

    citeulike


rss_1.0 rss_2.0 atom_1.0