Control of Flow Separation Using Electromagnetic Forces

Weier, Tom; Gerbeth, G.; Mutschke, Gerd; Lielausis, O.; Lammers, Gerd

doi:10.1023/b:appl.0000014922.98309.21

Cited by 55 publications

(29 citation statements)

References 12 publications

(8 reference statements)

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“…[20][21][22] Electromagnetic actuators are used for the control of turbulent channel flow, 23,24 for the suppression of vortex shedding behind a cylinder, 25,26 and to prevent flow separation past an airfoil. [27][28][29] The effect of electromagnetic forcing on self-sustained oscillations of a confined jet issuing into a thin cavity is investigated experimentally using particle image velocimetry (PIV). A permanent Lorentz force is imposed on the fluid by an electrical current across the width of the cavity in conjunction with a permanent magnetic field perpendicular to the electrical current.…”

Section: Introductionmentioning

confidence: 99%

Effects of electromagnetic forcing on self-sustained jet oscillations

et al. 2014

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The influence of electromagnetic forcing on self-sustained oscillations of a jet issuing from a submerged nozzle into a thin vertical cavity (width W much larger than thickness T) has been studied using particle image velocimetry. A permanent Lorentz force is produced by applying an electrical current across the width of the cavity in conjunction with a magnetic field from three permanent magnets across its thickness. As a working fluid a saline solution is used. The magnetic field is in the north-south-north configuration, such that the Lorentz force can be applied in an up-down-up configuration or in a down-up-down configuration by switching the direction of the electrical current. A critical Stuart number Nc was found. For N < Nc, the jet oscillates with a constant Strouhal number St, independent of the Reynolds number Re. For N > Nc and an oscillation enhancing up-down-up configuration of the Lorentz force, St grows with N as St \documentclass[12pt]{minimal}\begin{document}$\propto \sqrt{\mathrm{N}}$\end{document}∝N. In contrast, for N > Nc and an oscillation suppressing down-up-down configuration of the Lorentz force, all jet oscillations are suppressed.

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Section: Introductionmentioning

confidence: 99%

Effects of electromagnetic forcing on self-sustained jet oscillations

et al. 2014

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“…They have been used in a variety of fundamental and applied research in fluid mechanics, e.g. generation of chaotic and turbulent flows to study mixing [36,37], generation of vortices [38,39], drag reduction [40][41][42][43], flow separation delay [44], boundary layers manipulation [45], heat transfers enhancement [46,47] and turbulent-like flows e.g. [5,26].…”

Section: Electromagnetically Driven Flowsmentioning

confidence: 99%

Lamination and folding in electromagnetically driven flows of specified geometries

Rossi¹,

Lardeau²

2011

Journal of Turbulence

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In this paper, a new characterization and a quantification of lamination are presented. The lamination is identified by tracking material lines and by the estimation of the ratio between the length of the material lines within circles and the diameter of the circles. The quantification of the lamination rate relies on the interlaced structure of velocity and Lagrangian acceleration, which allows the determination of the spatial variation of the Lagrangian angular velocity. Those definitions are illustrated using quasi-steady flows driven by electromagnetic forces using mono-and multi-scale configurations with turbulent-like properties. Both experimental and numerical data are used to compute folding rate intensities and lamination for a large range of length scales. Good agreement is found between grid deformation and the prediction of lamination rate, an agreement further confirmed by the measure of lamination. The quantification of lamination is simple and well defined at chosen length-scales. Also, the present form applies to any lines and can be extended to 3D flows. The lamination rate process rely on physical quantities which scale according to the structures' length-scales. It is shown that the lamination rate increases with the reduction of the length-scales and in particular it is found thatṘ f ol ∼ ℓ −3/4 . In turbulent flows, the lamination should then be faster within small coherent structures. This quantification of lamination rate, complemented by a measure of lamination opens new routes for the description and the quantification of mixing in complex and turbulent flows.

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“…Weir et al [46] reported experimental results on the prevention of flow separation of an electrolyte with a relatively low electric conductivity, by applying a stream-wise, wall-parallel Lorentz force acting on the suction (upper) side of inclined flat plates and hydro-foils. The fully developed turbulent flow regime (1.2 × 10 5 ≤ Re ≤ 3.7 × 10 5 ) was considered for different intensities of applied electric currents, (50 ≤ I ≤ 1,000 A).…”

Section: Electromagnetic Control Of Pressure-driven Flowsmentioning

confidence: 99%

Large eddy simulations of targeted electromagnetic control of buoyancy-driven turbulent flow in a slender enclosure

Kenjereš

2009

Theor. Comput. Fluid Dyn.

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We conducted a large eddy simulation (LES) of a locally applied electromagnetic control of turbulent thermal convection of an electrically conductive fluid (electrolyte solution) inside of a slender enclosure. Generic configurations, consisting of two or three magnets of opposite polarities located below the lower wall, and two oppositely charged electrodes along the side walls, are considered. The neutral situation (pure thermal convection) is selected to be in turbulent regime at Ra = 10 7 , Pr = 7. A magnetically extended Smagorinsky type model for the subgrid turbulent stresses and a simple-gradient diffusion model for the subgrid turbulent heat fluxes are used. Different intensities of applied DC current through electrodes are imposed. The effects of the resulting Lorentz force on flow, turbulence reorganisation and wall-heat transfer are analysed. It is demonstrated that significant flow and turbulence structure reorganisation takes place in the proximity of the lower horizontal wall and in the central parts of the enclosure-even for weak DC current of I = 1 A. Significant turbulence increase, generated by the elevated electromagnetic mixing, produced significant enhancements of the wall-heat transfer-up to 70% for the 2-magnet configuration.

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Control of Flow Separation Using Electromagnetic Forces

Cited by 55 publications

References 12 publications

Effects of electromagnetic forcing on self-sustained jet oscillations

Effects of electromagnetic forcing on self-sustained jet oscillations

Lamination and folding in electromagnetically driven flows of specified geometries

Large eddy simulations of targeted electromagnetic control of buoyancy-driven turbulent flow in a slender enclosure

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