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Since the winggrid has a different topology
compared to other wing-tip devices, it is essential to classify
it and understand its effects.
Properties | Authors | ||
practical limit span_efficiency | Zimmer 83 | Kroo 95 | La Roche 96 |
parameter h/b compares vertical dimension h of configuration to span b | pure geometrical classification criteria | mix of geometry and downwash-wake criteria | downwash-wake parameters only vortex-spacing and vortex-core Spreiter & Sacks |
e=1.1 h/b=0 |
contour/straight | planar with nonplanar wake | contour |
e=1.4 with h/b=0.2 |
simple wingtips/ endplates |
nonplanar monoplane | endplate |
e=1.2 h/b>0.2 |
slotted edge/fanned partial | nonplanar monoplane |
open fanlike |
e=3.0 with h/b<0.05 for Winggrid |
N.A. | N.A. | closed multiple Winggrid/ Spiroid |
e=1.5 with h/b=0.2 |
N.A. | multiplanes/box/strut/ closed, C-Wing |
N.A. |
second row explains assessment criteria of the different authors
span efficiency is the efficiency relative to an elliptical wing
N.A. = not available
95 = year of publication
References:
H. Zimmer, The aerodynamic optimization of wings at subsonic speeds and the influence of wingtip design, NASA TM-88534 1987 (translation of dissertation, Stuttgart 83).
Ilan Kroo, John McMasters, Stephen C. Smith, Highly Nonplanar Lifting Systems, Transportation beyond 2000: technologies needed for engineering design, NASA Langley Research Center, Hampton, VA, September 26-28, 1995.
U. La Roche and S. Palffy, WING-GRID, a Novel Device for Reduction of Induced Drag on Wings, Proceedings ICAS 96, Sorrento, ITALY, September 8-13, 1996.
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Updated: 23 February, 1999