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International Journal of Fluid Mechanics Research

ISSN Print: 1064-2277
ISSN Online: 2152-5102

International Journal of Fluid Mechanics Research

DOI: 10.1615/InterJFluidMechRes.v28.i1-2.140
pages 185-195

Dynamics of a Vortex in an Angular Region and within a Cross Groove

V. O. Gorban
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
I. M. Gorban
Institute of Hydromechanics of National Academy of Sciences of Ukraine, Kyiv, Ukraine

ABSTRACT

The paper deals with a numerical simulation of behaviour of two-dimensional stationary vortices in the near-wall flow that develops either in an angular region or within a cross groove. The model of ideal incompressible fluid is used. The complex potential of flow is determined by conformal transformation of physical area into the upper half-plane of auxiliary plane. The strength and coordinates of the stationary vortices were obtained against geometrical parameters that characterize the flow area. The stationary vortex was shown to have characteristic eigenfrequency. It corresponds to the frequency of the vortex precession about the stationary point under small departure of the vortex from its equilibrium. Due to eigenfrequency, both the stationary vortex and the local separation zone generated by that respond selectively on periodic perturbations of the free-stream velocity. These external disturbances cause departure of the vortex from its equilibrium. As a result, the vortex moves periodically along a closed trajectory of finite amplitude. Dependence of the amplitude of this motion on the frequency of external perturbations is resonant one. When the frequency of external perturbation is near the vortex eigenfrequency, the amplitude of the vortex motion increases abruptly that leads to intensification of mixing as well as to chaotization of motion in the local circulation zones generated by stationary vortices.