Control of external flows via electro-magnetic fields

Crawford, Catherine H.; Karniadakis, George

doi:10.2514/6.1995-2185

Cited by 13 publications

(9 citation statements)

References 5 publications

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“…Therefore, Eq. ͑5͒ does not have to be solved in time, 12 hence the computational work is reduced significantly. For fluids with higher conductivity ͑e.g., mercury͒ the coupled system of flow equations and field equations is solved ͑see Ref.…”

Section: Jϭ͑eϩu؋b͒ ͑2͒mentioning

confidence: 99%

“…II͒, similar to the magnetic-only excitation for highly conducting fluids. In recent numerical work 12 we have applied magnetic and electromagnetic fields to modify wake flows corresponding to both high and low conductivity fluids. We have demonstrated that modest field strength is required in order to suppress a vortex street or inhibit pairing of vortices preventing subharmonic instabilities or reduce and even eliminate three dimensionality in a flow.…”

Section: Introductionmentioning

confidence: 99%

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Reynolds stress analysis of EMHD-controlled wall turbulence. Part I. Streamwise forcing

Crawford

Karniadakis

1997

Physics of Fluids

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In this work we investigate numerically turbulent flow of low electrical conductivity fluid subject to electromagnetic ͑EMHD͒ forcing. The configuration is similar to the one considered in the experimental work of Henoch and Stace ͓Phys. Fluids 7, 1371 ͑1995͔͒ but in a channel geometry. The lower wall of the channel is covered with alternating streamwise electrodes and magnets to create a Lorentz force in the positive streamwise direction. Two cases are considered in detail corresponding to interaction parameter values of 0.4 ͑case 1͒ and 0.1 ͑case 2͒. The effect of switching off and on the electrodes is also studied for the two cases. At the Reynolds number considered ͑Re Ϸ200͒, a drag increase was obtained for all cases, in agreement with the experiments of Henoch and Stace. A Reynolds stress analysis was performed based on a new decomposition of the gradients normal to the wall of the Reynolds stress ϪuЈvЈ. It was found that the vortex stretching term wЈw 2 Ј and the spanwise variation of the stress component uЈwЈ are responsible for the drag increase. More specifically, the term ‫(ץ‬uЈwЈ)/‫ץ‬x 3 is associated with secondary vortical motions in the near-wall and becomes large and positive for large shear stress in regions where fluid is moving toward the wall. In contrast, negative values are associated with regions of lower shear where fluid is being lifted away from the wall. Unlike the unperturbed flow, in the controlled flow high speed near-wall streamwise jets are present ͑case 1͒ even in the time-averaged fields. Other changes in turbulence structure are quantified using streak spacing, vortex lines, vorticity quadrant analysis, and plots of the rms value of the vorticity angle.

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Section: Jϭ͑eϩu؋b͒ ͑2͒mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Reynolds stress analysis of EMHD-controlled wall turbulence. Part I. Streamwise forcing

Crawford

Karniadakis

1997

Physics of Fluids

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“…In the recent years, the Lorentz force has attracted more attention due to its promising applications in engineering fields. Crawford and Karniadakis [35] has numerically investigated that the Lorentz force can eliminate the flow separation when the flow past a stationary cylinder, and the suppressing effect of the Lorentz force has been confirmed by Weier et al [36] with both experiments and calculations. Later, in the cases of Kim and Lee [37] and Posdziech and Grundmann [38], it is found that both of the continuous and pulsed Lorentz forces can suppress the force fluctuation and stabilize the flow.…”

Section: Governing Equationsmentioning

confidence: 82%

Investigations on the Effects of Vortex-Induced Vibration with Different Distributions of Lorentz Forces

et al. 2017

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Abstract:The control of vortex-induced vibration (VIV) in shear flow with different distributions of Lorentz force is numerically investigated based on the stream function-vorticity equations in the exponential-polar coordinates exerted on moving cylinder for Re = 150. The cylinder motion equation coupled with the fluid, including the mathematical expressions of the lift force coefficient C l , is derived. The initial and boundary conditions as well as the hydrodynamic forces on the surface of cylinder are also formulated. The Lorentz force applied to suppress the VIV has no relationship with the flow field, and involves two categories, i.e., the field Lorentz force and the wall Lorentz force. With the application of symmetrical Lorentz forces, the symmetric field Lorentz force can amplify the drag, suppress the flow separation, decrease the lift fluctuation, and then suppress the VIV while the wall Lorentz force decreases the drag only. With the application of asymmetrical Lorentz forces, besides the above-mentioned effects, the field Lorentz force can increase additional lift induced by shear flow, whereas the wall Lorentz force can counteract the additional lift, which is dominated on the total effect.

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“…The relevant list of parameters is shown in Table III. Note that external fields can either suppress or enhance the vortex street as has been found in experimental and numerical work for incompressible flows [36][37][38].…”

Section: Table III Simulation Parameters For Compressible Flow Past Amentioning

confidence: 98%

A Discontinuous Galerkin Method for the Viscous MHD Equations

Warburton

Karniadakis

1999

Journal of Computational Physics

126

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Control of external flows via electro-magnetic fields

Cited by 13 publications

References 5 publications

Reynolds stress analysis of EMHD-controlled wall turbulence. Part I. Streamwise forcing

Reynolds stress analysis of EMHD-controlled wall turbulence. Part I. Streamwise forcing

Investigations on the Effects of Vortex-Induced Vibration with Different Distributions of Lorentz Forces

A Discontinuous Galerkin Method for the Viscous MHD Equations

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