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 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

The effect of a 70 deg swept canard on the leading-edge vortices of a 70 deg swept delta wing during dynamic pitching

1997 ◽  
Author(s):  
Shigeo Hayashibara ◽  
Roy Myose ◽  
L. Miller ◽  
Shigeo Hayashibara ◽  
Roy Myose ◽  
...  
Keyword(s):  
Delta Wing ◽  
Leading Edge ◽  
Leading Edge Vortices

scholarly journals Secondary Flow Control in Low Aspect Ratio Vanes Using Splitters

2016 ◽  
Author(s):  
Christopher Clark ◽  
Graham Pullan ◽  
Eric Curtis ◽  
Frederic Goenaga
Keyword(s):  
Kinetic Energy ◽  
Aspect Ratio ◽  
Secondary Flow ◽  
Current Practice ◽  
Leading Edge ◽  
Horseshoe Vortex ◽  
Secondary Flows ◽  
Optimization Approach ◽  
Flow Strength ◽  
Low Aspect Ratio

Low aspect ratio vanes, often the result of overall engine architecture constraints, create strong secondary flows and high endwall loss. In this paper, a splitter concept is demonstrated that reduces secondary flow strength and improves stage performance. An analytic conceptual study, corroborated by inviscid computations, shows that the total secondary kinetic energy of the secondary flow vortices is reduced when the number of passages is increased and, for a given number of vanes, when the inlet endwall boundary layer is evenly distributed between the passages. Viscous computations show that, for this to be achieved in a splitter configuration, the pressure-side leg of the low aspect ratio vane horseshoe vortex, must enter the adjacent passage (and not “jump” in front of the splitter leading edge). For a target turbine application, four vane designs were produced using a multi-objective optimization approach. These designs represent: current practice for a low aspect ratio vane; a design exempt from thickness constraints; and two designs incorporating splitter vanes. Each geometry is tested experimentally, as a sector, within a low-speed turbine stage. The vane designs with splitters geometries were found to reduce the measured secondary kinetic energy, by up to 85%, to a value similar to the design exempt from thickness constraints. The resulting flowfield was also more uniform in both the circumferential and radial directions. One splitter design was selected for a full annulus test where a mixed-out loss reduction, compared to the current practice design, of 15.3% was measured and the stage efficiency increased by 0.88%.

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