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Instability and transition to turbulence in a free shear layer affected by a parallel magnetic field

Instability and transition to turbulence in a free shear layer affected by a parallel magnetic field
Instability and transition to turbulence in a free shear layer affected by a parallel magnetic field
Instability and transition to turbulence in a temporally evolving free shear layer of an electrically conducting fluid affected by an imposed parallel magnetic field is investigated numerically. The case of low magnetic Reynolds number is considered. It has long been known that the neutral disturbances of the linear problem are three-dimensional at sufficiently strong magnetic fields. We analyse the details of this instability solving the generalized Orr–Sommerfeld equation to determine the wavenumbers, growth rates and spatial shapes of the eigenmodes. The three-dimensional perturbations are identified as oblique waves and their properties are described. In particular, we find that at high hydrodynamic Reynolds number, the effect of the strength of the magnetic field on the fastest growing perturbations is limited to an increase of their oblique angle. The dimensions and spatial shape of the waves remain unchanged. The transition to turbulence triggered by the growing oblique waves is investigated in direct numerical simulations. It is shown that initial perturbations in the form of superposition of two symmetric waves are particularly effective in inducing three-dimensionality and turbulence in the flow.
0022-1120
131-154
Vorobev, A.
911a4e1e-0c34-4297-b52e-c22a2b9dec01
Zikanov, O.
7edaa777-6e8e-4128-af46-f0803c1374a7
Vorobev, A.
911a4e1e-0c34-4297-b52e-c22a2b9dec01
Zikanov, O.
7edaa777-6e8e-4128-af46-f0803c1374a7

Vorobev, A. and Zikanov, O. (2007) Instability and transition to turbulence in a free shear layer affected by a parallel magnetic field. Journal of Fluid Mechanics, 574, 131-154. (doi:10.1017/S002211200600423X).

Record type: Article

Abstract

Instability and transition to turbulence in a temporally evolving free shear layer of an electrically conducting fluid affected by an imposed parallel magnetic field is investigated numerically. The case of low magnetic Reynolds number is considered. It has long been known that the neutral disturbances of the linear problem are three-dimensional at sufficiently strong magnetic fields. We analyse the details of this instability solving the generalized Orr–Sommerfeld equation to determine the wavenumbers, growth rates and spatial shapes of the eigenmodes. The three-dimensional perturbations are identified as oblique waves and their properties are described. In particular, we find that at high hydrodynamic Reynolds number, the effect of the strength of the magnetic field on the fastest growing perturbations is limited to an increase of their oblique angle. The dimensions and spatial shape of the waves remain unchanged. The transition to turbulence triggered by the growing oblique waves is investigated in direct numerical simulations. It is shown that initial perturbations in the form of superposition of two symmetric waves are particularly effective in inducing three-dimensionality and turbulence in the flow.

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Published date: March 2007

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Local EPrints ID: 48862
URI: http://eprints.soton.ac.uk/id/eprint/48862
ISSN: 0022-1120
PURE UUID: 35eecd88-7e7c-4d4c-aa4e-e0567817327a
ORCID for A. Vorobev: ORCID iD orcid.org/0000-0002-6458-9390

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Date deposited: 16 Oct 2007
Last modified: 16 Mar 2024 03:57

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Contributors

Author: A. Vorobev ORCID iD
Author: O. Zikanov

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