Instability and merging of a helical vortex pair in the wake of a rotor

This paper establishes the drag characteristics of finite cylinders of aspect ratio 1, 4, 10 and 100 for Reynolds numbers less than 1000 including the viscous regime. The effect of the drag and vortex shedding characteristics of curving a finite cylinder into a toroidal shape is investigated. The curvature reduces drag by as much as 13 percent over its linear counterpart in the viscous regime. Vortex shedding characteristics of tori include all the features of cylinders in addition to a solidity range that behaves like solid bodies and an intermediate range where two vortex flow patterns can exist. These patterns can occur either as alternating ring vortices or a less common but more stable counterrotating helical vortex pair.

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

AIAA Journal ◽

10.2514/3.13987 ◽

1998 ◽

Vol 36 ◽

pp. 1439-1445 ◽

Cited By ~ 2

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

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Kelvin waves on helical vortex tube in swirling flow

Journal of Physics Conference Series ◽

10.1088/1742-6596/980/1/012003 ◽

2018 ◽

Vol 980 ◽

pp. 012003

Author(s):

M A Tsoy ◽

S G Skripkin ◽

P A Kuibin ◽

S I Shtork ◽

S V Alekseenko

Keyword(s):

Vortex Tube ◽

Swirling Flow ◽

Kelvin Waves ◽

Helical Vortex

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

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/0954410020987430 ◽

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.

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Onset of chaos in helical vortex breakdown at low Reynolds number

Physical Review Fluids ◽

10.1103/physrevfluids.3.064701 ◽

2018 ◽

Vol 3 (6) ◽

Cited By ~ 2

Author(s):

S. Pasche ◽

F. Avellan ◽

F. Gallaire

Keyword(s):

Reynolds Number ◽

Vortex Breakdown ◽

Low Reynolds Number ◽

Onset Of Chaos ◽

Helical Vortex ◽

Low Reynolds

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Topological bifurcations of vortex pair interactions

Journal of Fluid Mechanics ◽

10.1017/jfm.2021.191 ◽

2021 ◽

Vol 917 ◽

Author(s):

Anne R. Nielsen ◽

Morten Andersen ◽

Jesper S. Hansen ◽

Morten Brøns

Keyword(s):

Vortex Pair ◽

Pair Interactions

Abstract

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The approach of a vortex pair to a plane surface in inviscid fluid

Journal of Fluid Mechanics ◽

10.1017/s0022112079000744 ◽

1979 ◽

Vol 92 (3) ◽

pp. 497-503 ◽

Cited By ~ 55

Author(s):

P. G. Saffman

Keyword(s):

Approximate Calculation ◽

Plane Surface ◽

Vortex Pair ◽

Plane Wall ◽

Inviscid Fluid ◽

Viscous Effects ◽

Axis Ratio ◽

Local Rate

It is shown that a symmetrical vortex pair consisting of equal and opposite vortices approaching a plane wall at right angles must approach the wall monotonically in the absence of viscous effects. An approximate calculation is carried out for uniform vortices in which the vortices are assumed to be deformed into ellipses whose axis ratio is determined by the local rate of strain according to the results of Moore & Saffman (1971).

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Steady longitudinal vortices in supersonic turbulent separated flows

Journal of Fluid Mechanics ◽

10.1017/s0022112010006105 ◽

2011 ◽

Vol 672 ◽

pp. 451-476 ◽

Cited By ~ 14

Author(s):

ERICH SCHÜLEIN ◽

VICTOR M. TROFIMOV

Keyword(s):

High Speed ◽

Large Scale ◽

Roughness Element ◽

Vortex Generator ◽

Vortex Pair ◽

Leading Edge ◽

Separated Flows ◽

Vortex Generators ◽

Longitudinal Vortices ◽

Oil Flow

Large-scale longitudinal vortices in high-speed turbulent separated flows caused by relatively small irregularities at the model leading edges or at the model surfaces are investigated in this paper. Oil-flow visualization and infrared thermography techniques were applied in the wind tunnel tests at Mach numbers 3 and 5 to investigate the nominally 2-D ramp flow at deflection angles of 20°, 25° and 30°. The surface contour anomalies have been artificially simulated by very thin strips (vortex generators) of different shapes and thicknesses attached to the model surface. It is shown that the introduced streamwise vortical disturbances survive over very large downstream distances of the order of 104 vortex-generator heights in turbulent supersonic flows without pressure gradients. It is demonstrated that each vortex pair induced in the reattachment region of the ramp is definitely a child of a vortex pair, which was generated originally, for instance, by the small roughness element near the leading edge. The dependence of the spacing and intensity of the observed longitudinal vortices on the introduced disturbances (thickness and spanwise size of vortex generators) and on the flow parameters (Reynolds numbers, boundary-layer thickness, compression corner angles, etc.) has been shown experimentally.

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