• Journal of Aerospace System Engineering
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• v.10 no.1
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• pp.1-7
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• 2016

During flight of the aircraft, the vortex merging phenomenon appears under the certain condition between co-rotating vortices which were generated at the wing tip and lifting-surface. And then these merged vortices at both sides show counter-rotating pattern to affect on the downstream of the aircraft. In this paper, the numerical simulations are conducted assuming this phenomenon in two-dimensional co-rotating or counter-rotating vortices pairs. Two-dimensional incompressible Navier-Stokes equations were converted into Vorticity-Streamfunction form and the Galerkin spectral method was adopted. The third order Runge-Kutta method was used for time integration. The effects on the vortex merger and degree of vortex merger were investigated according to time, Reynolds number, and changes in the distance between two vortices.

• Wind and Structures
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• v.5 no.2_3_4
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• pp.141-150
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• 2002

Numerical simulations based on the ALE finite element method are carried out to examine the aerodynamics of an oscillating circular cylinder when the separated shear flows around the cylinder are stimulated by periodic jet excitation with a shear layer instability frequency. The excitation is applied to the flows from two points on the cylinder surface. The numerical results showed that the excitation with a shear layer instability frequency can reduce the negative damping and thereby stabilize the aerodynamics of the oscillating cylinder. The change of the lift phase seems important in stabilizing the cylinder aerodynamics. The change of lift phase is caused by the merger of the vortices induced by the periodic excitation with a shear layer instability frequency, and the vortex merging comes from the high growth rate, the rapid increase of wave number and decrease of phase velocity for the periodic excitation in the separated shear flows.