Investigating sweep effects on the stability of leading-edge vortices over finite-aspect ratio pitch-up wings

2021 ◽  
Vol 33 (10) ◽  
pp. 107104
Author(s):  
Rozie Zangeneh
Keyword(s):  
Aspect Ratio ◽  
Leading Edge ◽  
The Stability ◽  
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

The stability of leading-edge vortices to perturbations on samara-inspired rotors: a novel solution for gust resistance

2019 ◽  
Vol 15 (1) ◽  
pp. 016006
Author(s):  
Adnan M El Makdah ◽  
Laura Sanders ◽  
Kai Zhang ◽  
David E Rival
Keyword(s):  
Leading Edge ◽  
The Stability ◽  
Leading Edge Vortices

The role of advance ratio and aspect ratio in determining leading-edge vortex stability for flapping flight

2014 ◽  
Vol 751 ◽  
pp. 71-105 ◽  
Author(s):  
R. R. Harbig ◽  
J. Sheridan ◽  
M. C. Thompson
Keyword(s):  
Aspect Ratio ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Leading Edge Vortex ◽  
Aspect Ratios ◽  
Edge Vortex ◽  
Advance Ratio ◽  
Vorticity Production ◽  
The Stability

AbstractThe effects of advance ratio and the wing’s aspect ratio on the structure of the leading-edge vortex (LEV) that forms on flapping and rotating wings under insect-like flight conditions are not well understood. However, recent studies have indicated that they could play a role in determining the stable attachment of the LEV. In this study, a numerical model of a flapping wing at insect Reynolds numbers is used to explore the effects of these parameters on the characteristics and stability of the LEV. The word ‘stability’ is used here to describe whether the LEV was attached throughout the stroke or if it was shed. It is demonstrated that increasing the advance ratio enhances vorticity production at the leading edge during the downstroke, and this results in more rapid growth of the LEV for non-zero advance ratios. Increasing the wing aspect ratio was found to have the effect of shortening the wing’s chord length relative to the LEV’s size. These two effects combined determine the stability of the LEV. For high advance ratios and large aspect ratios, the LEV was observed to quickly grow to envelop the entire wing during the early stages of the downstroke. Continued rotation of the wing resulted in the LEV being eventually shed as part of a vortex loop that peels away from the wing’s tip. The shedding of the LEV for high-aspect-ratio wings at non-zero advance ratios leads to reduced aerodynamic performance of these wings, which helps to explain why a number of insect species have evolved to have low-aspect-ratio wings.

The influence of leading-edge deflection on the stability of the leading-edge vortices

2020 ◽  
Vol 234 (20) ◽  
pp. 3992-4008
Author(s):  
Jiao-Long Zhang ◽  
Jun-Hu ◽  
Yong Yu ◽  
Hai-Bin Xuan
Keyword(s):  
Topological Analysis ◽  
Three Dimensional ◽  
Leading Edge ◽  
Leading Edge Vortex ◽  
Eddy Simulation ◽  
Symmetric Plane ◽  
Edge Vortex ◽  
The Stability ◽  
Secondary Vortices ◽  
Leading Edge Vortices

To examine the effect of leading-edge deflected angle [Formula: see text] on the stability of the leading-edge vortex, the three-dimensional flow field of a flapping wing is simulated by a numerical method. The multi domain mesh generation, dynamic mesh and large eddy simulation technology are employed to capture the finer flowfield structure. The wings perform pure periodic oscillations, and the Reynolds number ( Re) is 4527 based on the chord length c. The folding line formed after the deflection coincides with the pitch axis and is located at the 1/4 c from the leading edge. The results show that the increase of [Formula: see text] maintains the strength of the leading-edge vortex for longer time, and weakens the influence of the motion of the wing on the leading-edge vortex intensity. The flowfield topological analysis shows that the increase of [Formula: see text] also prevents the formation of secondary vortices between the wing surface and the leading-edge vortices, which indirectly contributes to the attachment of the leading-edge vortices to the wing. Moreover, the vortex dynamics equations have been analyzed, and the results indicate that the increase of [Formula: see text] will delay the occurrence of spanwise convection of vorticity and weaken its intensity. In addition, it can also suppress the spanwise flow behind the leading-edge vortices toward the symmetric plane. As a result, increasing [Formula: see text] stabilizes the boundary layer in this region and thereby stabilizes the leading-edge vortices indirectly. Finally, a new parameter is introduced to quantitatively evaluate the proximity of the leading-edge vortex to the surface of the plate. Our method comprehensively considers the influence of the leading-edge vortex scale and the core motion on the approaching of the leading-edge vortex to the wing, and some important conclusions on the developing law of the leading-edge vortex, which are agreement with the experimental measurement, are obtained.

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.

Vortical substructures in the shear layers forming leading-edge vortices

AIAA Journal ◽  
2002 ◽  
Vol 40 ◽  
pp. 1689-1692 ◽  
Author(s):  
A. M. Mitchell ◽  
P. Molton
Keyword(s):  
Leading Edge ◽  
Shear Layers ◽  
Leading Edge Vortices

Scaling the vorticity dynamics in the leading-edge vortices of revolving wings with two directional length scales

2020 ◽  
Vol 32 (12) ◽  
pp. 121903
Author(s):  
Nathaniel H. Werner ◽  
Junshi Wang ◽  
Haibo Dong ◽  
Azar Eslam Panah ◽  
Bo Cheng
Keyword(s):  
Leading Edge ◽  
Length Scales ◽  
Vorticity Dynamics ◽  
Leading Edge Vortices
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