Three-dimensionality of leading-edge vortices on high aspect ratio plunging wings

2020 ◽  
Vol 5 (6) ◽  
Author(s):  
N. Chiereghin ◽  
S. Bull ◽  
D. J. Cleaver ◽  
I. Gursul
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Leading Edge ◽  
Leading Edge Vortices

scholarly journals On the stabilization of leading-edge vortices with different reduced frequencies over finite-aspect-ratio pitch-up wings

AIP Advances ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 025029
Author(s):  
JiaoLong Zhang ◽  
Jun Hu ◽  
Yong Yu ◽  
HaiBin Xuan
Keyword(s):  
Aspect Ratio ◽  
Leading Edge ◽  
Leading Edge Vortices

scholarly journals Power reduction and the radial limit of stall delay in revolving wings of different aspect ratio

2015 ◽  
Vol 12 (105) ◽  
pp. 20150051 ◽  
Author(s):  
Jan W. Kruyt ◽  
GertJan F. van Heijst ◽  
Douglas L. Altshuler ◽  
David Lentink
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Angle Of Attack ◽  
Radial Distance ◽  
Leading Edge ◽  
High Angle ◽  
High Angle Of Attack ◽  
Low Aspect Ratio ◽  
Aspect Ratios ◽  
Low Aspect Ratio Wings

Airplanes and helicopters use high aspect ratio wings to reduce the power required to fly, but must operate at low angle of attack to prevent flow separation and stall. Animals capable of slow sustained flight, such as hummingbirds, have low aspect ratio wings and flap their wings at high angle of attack without stalling. Instead, they generate an attached vortex along the leading edge of the wing that elevates lift. Previous studies have demonstrated that this vortex and high lift can be reproduced by revolving the animal wing at the same angle of attack. How do flapping and revolving animal wings delay stall and reduce power? It has been hypothesized that stall delay derives from having a short radial distance between the shoulder joint and wing tip, measured in chord lengths. This non-dimensional measure of wing length represents the relative magnitude of inertial forces versus rotational accelerations operating in the boundary layer of revolving and flapping wings. Here we show for a suite of aspect ratios, which represent both animal and aircraft wings, that the attachment of the leading edge vortex on a revolving wing is determined by wing aspect ratio, defined with respect to the centre of revolution. At high angle of attack, the vortex remains attached when the local radius is shorter than four chord lengths and separates outboard on higher aspect ratio wings. This radial stall limit explains why revolving high aspect ratio wings (of helicopters) require less power compared with low aspect ratio wings (of hummingbirds) at low angle of attack and vice versa at high angle of attack.

The aerodynamics of revolving wings II. Propeller force coefficients from mayfly to quail

2002 ◽  
Vol 205 (11) ◽  
pp. 1565-1576 ◽  
Author(s):  
James R. Usherwood ◽  
Charles P. Ellington
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Normal Force ◽  
Large Range ◽  
Leading Edge ◽  
Force Coefficients ◽  
Aspect Ratios ◽  
The Relationship ◽  
Force Relationship ◽  
Leading Edge Vortices

SUMMARYHigh force coefficients, similar to those observed for revolving model hawkmoth wings in the accompanying paper (for which steady leading-edge vortices are directly observed), are apparent for revolving model (mayfly,bumblebee and quail) and real (quail) animal wings ranging in Reynolds number(Re) from 1100 to 26000. Results for bumblebee and hawkmoth wings agree with those published previously for Drosophila(Re≈200). The effect of aspect ratio is also tested with planforms based on hawkmoth wings adjusted to aspect ratios ranging from 4.53 to 15.84 and is shown to be relatively minor, especially at angles of incidence below 50°.The normal force relationship introduced in the accompanying paper is supported for wings over a large range of aspect ratios in both `early' and`steady' conditions; local induced velocities appear not to affect the relationship.

Aeroelastic Simulation of High-Aspect Ratio Wings with Intermittent Leading-Edge Separation

AIAA Journal ◽  
2021 ◽  
pp. 1-14
Author(s):  
Yinan Wang ◽  
Xiaowei Zhao ◽  
Rafael Palacios ◽  
Keisuke Otsuka
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Leading Edge ◽  
Edge Separation
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