Unsteady Nature of Vortex Pair in Formation Flight

2017 ◽  
Author(s):  
Chen Chen ◽  
Zhijin Wang ◽  
Ismet Gursul
Keyword(s):  
Vortex Pair ◽  
Formation Flight

Optimum Downwash Behind Wings in Formation Flight

10.2514/1.20 ◽  
2003 ◽  
Vol 40 (4) ◽  
Author(s):  
Ashok Gopalarathnam ◽  
James W. Frazier
Keyword(s):  
Formation Flight

Large-eddy simulations and lidar measurements of vortex-pair breakup in aircraft wakes

AIAA Journal ◽  
1998 ◽  
Vol 36 ◽  
pp. 1439-1445 ◽  
Author(s):  
D. C. Lewellen ◽  
W. S. Lewellen ◽  
L. R. Poole ◽  
C. A. Hostetler ◽  
R. J. DeCoursey ◽  
...  
Keyword(s):  
Vortex Pair ◽  
Large Eddy Simulations ◽  
Large Eddy ◽  
Lidar Measurements

Structure and behavior of white pelican formation flocks

1982 ◽  
Vol 60 (6) ◽  
pp. 1388-1396 ◽  
Author(s):  
J. Brian E. O'Malley ◽  
Roger M. Evans
Keyword(s):  
Response Times ◽  
Formation Flight ◽  
Flock Size ◽  
Wingbeat Frequency ◽  
Percent Time ◽  
Column Formation ◽  
Highly Correlated ◽  
And Behavior

Observations of white pelicans commuting between nesting colonies and foraging areas revealed transitions from small, simple linear flock formations to larger, more complex vee and jay formations during departures, and the reverse during the return approach. Large, less-organized types of formations were relatively uncommon and short lived.Formation angles measured for filmed flocks ranged from 24° to 122° and were highly correlated with mean relative interbird distances within flocks. The number of wingbeats per hour, calculated from wingbeat frequency (beats per minute) and percent time flapping, was lowest in vee formation, progressively greater in jay, echelon, and column formation, and greatest for single birds. Wingbeats per hour decreased behind the lead bird, which usually had the highest rate, within each type of formation.Shifts between flapping and gliding were usually initiated by lead birds. Response times for these shifts were negatively related to flock size, and were shorter in vee and jay formations than in column and echelon formations.Our data suggests formation flight provides both aerodynamic–energetic and communication advantages over solitary flight.

Study on the influence of linear and nonlinear distribution of crosswind on the motion of aircraft wake vortex

2021 ◽  
pp. 095441002098743
Author(s):  
Dong Li ◽  
Ziming Xu ◽  
Ke Zhang ◽  
Zeyu Zhang ◽  
Jinxin Zhou ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Dissipation Rate ◽  
Vortex Pair ◽  
Vertical Shear ◽  
Wake Vortex ◽  
Analysis Method ◽  
Velocity Magnitude ◽  
Aircraft Wake ◽  
Linear And Nonlinear ◽  
Nonlinear Distribution

Environmental crosswind can greatly affect the development of aircraft wake vortex pair. Previous numerical simulations and experiments have shown that the nonlinear vertical shear of the crosswind velocity can affect the dissipation rate of the aircraft wake vortex, causing each vortex of the vortex pair descent with different velocity magnitude, which will lead to the asymmetrical settlement and tilt of the wake vortex pair. Through numerical simulations, this article finds that uniform crosswind convection and linear vertical shear crosswind convection can also have an effect on the strength of the vortex. This effect is inversely proportional to the cube of the vortex spacing, so it is more intense on small separation vortex pair. In addition, the superposition of crosswind and vortex-induced velocities will lead to the asymmetrical pressure distribution around the vortex pair, which will also cause the tilt of the vortex pair. Furthermore, a new analysis method for wake vortex is proposed, which can be used to predict the vortex trajectory.

scholarly journals Pose Measurement for Unmanned Aerial Vehicle Based on Rigid Skeleton

2021 ◽  
Vol 11 (4) ◽  
pp. 1373
Author(s):  
Jingyu Zhang ◽  
Zhen Liu ◽  
Guangjun Zhang
Keyword(s):  
Measurement Errors ◽  
Structural Characteristics ◽  
Geometric Model ◽  
Formation Flight ◽  
Depth Information ◽  
Feature Points ◽  
Feature Point Extraction ◽  
Aerial Vehicle ◽  
Uav Navigation ◽  
Rigid Skeleton

Pose measurement is a necessary technology for UAV navigation. Accurate pose measurement is the most important guarantee for a UAV stable flight. UAV pose measurement methods mostly use image matching with aircraft models or 2D points corresponding with 3D points. These methods will lead to pose measurement errors due to inaccurate contour and key feature point extraction. In order to solve these problems, a pose measurement method based on the structural characteristics of aircraft rigid skeleton is proposed in this paper. The depth information is introduced to guide and label the 2D feature points to eliminate the feature mismatch and segment the region. The space points obtained from the marked feature points fit the space linear equation of the rigid skeleton, and the UAV attitude is calculated by combining with the geometric model. This method does not need cooperative identification of the aircraft model, and can stably measure the position and attitude of short-range UAV in various environments. The effectiveness and reliability of the proposed method are verified by experiments on a visual simulation platform. The method proposed can prevent aircraft collision and ensure the safety of UAV navigation in autonomous refueling or formation flight.

scholarly journals Topological bifurcations of vortex pair interactions

2021 ◽  
Vol 917 ◽  
Author(s):  
Anne R. Nielsen ◽  
Morten Andersen ◽  
Jesper S. Hansen ◽  
Morten Brøns
Keyword(s):  
Vortex Pair ◽  
Pair Interactions

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