Transition to turbulence in Hunt's flow in a moderate magnetic field

Lee Andrew Braiden, D. Krasnov, Sergei Molokov, T. Boeck, L. Buhler

Research output: Contribution to journalLetter

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Abstract

Pressure-driven magnetohydrodynamic duct flow in a transverse uniform magnetic field is studied by direct numerical simulation. The electric boundary conditions correspond to Hunt's flow with perfectly insulating walls parallel to the magnetic field (sidewalls) and perfectly conducting walls perpendicular to the magnetic field (Hartmann walls). The velocity distribution exhibits strong jets at the sidewalls, which are susceptible to instability even at low Reynolds numbers Re. We explore the onset of time-dependent flow and transition to states with evolved turbulence for a moderate Hartmann number $Ha = 100$ . At low Re time-dependence appears in the form of elongated Ting-Walker vortices at the sidewalls of the duct, which, upon increasing Re, develop into more complex structures with higher energy and then the sidewall jets partially detach from the walls. At high values of Re jet detachments disappear and the flow consists of two turbulent jets and nearly laminar core. It is also demonstrated that, there is a range of Re, where Hunt's flow exhibits a pronounced hysteresis behavior, so that different unsteady states can be observed for the same flow parameters. In this range multiple states may develop and co-exist, depending on the initial conditions.
Original languageEnglish
Article number44002
JournalEPL
Volume115
Issue number4
DOIs
Publication statusPublished - 21 Sep 2016

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turbulence
magnetic fields
ducts
Hartmann number
unsteady state
turbulent jets
low Reynolds number
direct numerical simulation
detachment
magnetohydrodynamics
time dependence
velocity distribution
hysteresis
vortices
boundary conditions
conduction
energy

Bibliographical note

The paper is not currently available on the repository. There is a 12 month embargo until 21 September 2017.

Cite this

Braiden, L. A., Krasnov, D., Molokov, S., Boeck, T., & Buhler, L. (2016). Transition to turbulence in Hunt's flow in a moderate magnetic field. EPL, 115(4), [44002]. https://doi.org/10.1209/0295-5075/115/44002

Transition to turbulence in Hunt's flow in a moderate magnetic field. / Braiden, Lee Andrew; Krasnov, D.; Molokov, Sergei; Boeck, T.; Buhler, L.

In: EPL, Vol. 115, No. 4, 44002, 21.09.2016.

Research output: Contribution to journalLetter

Braiden, LA, Krasnov, D, Molokov, S, Boeck, T & Buhler, L 2016, 'Transition to turbulence in Hunt's flow in a moderate magnetic field' EPL, vol. 115, no. 4, 44002. https://doi.org/10.1209/0295-5075/115/44002
Braiden LA, Krasnov D, Molokov S, Boeck T, Buhler L. Transition to turbulence in Hunt's flow in a moderate magnetic field. EPL. 2016 Sep 21;115(4). 44002. https://doi.org/10.1209/0295-5075/115/44002
Braiden, Lee Andrew ; Krasnov, D. ; Molokov, Sergei ; Boeck, T. ; Buhler, L. / Transition to turbulence in Hunt's flow in a moderate magnetic field. In: EPL. 2016 ; Vol. 115, No. 4.
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abstract = "Pressure-driven magnetohydrodynamic duct flow in a transverse uniform magnetic field is studied by direct numerical simulation. The electric boundary conditions correspond to Hunt's flow with perfectly insulating walls parallel to the magnetic field (sidewalls) and perfectly conducting walls perpendicular to the magnetic field (Hartmann walls). The velocity distribution exhibits strong jets at the sidewalls, which are susceptible to instability even at low Reynolds numbers Re. We explore the onset of time-dependent flow and transition to states with evolved turbulence for a moderate Hartmann number $Ha = 100$ . At low Re time-dependence appears in the form of elongated Ting-Walker vortices at the sidewalls of the duct, which, upon increasing Re, develop into more complex structures with higher energy and then the sidewall jets partially detach from the walls. At high values of Re jet detachments disappear and the flow consists of two turbulent jets and nearly laminar core. It is also demonstrated that, there is a range of Re, where Hunt's flow exhibits a pronounced hysteresis behavior, so that different unsteady states can be observed for the same flow parameters. In this range multiple states may develop and co-exist, depending on the initial conditions.",
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AU - Braiden, Lee Andrew

AU - Krasnov, D.

AU - Molokov, Sergei

AU - Boeck, T.

AU - Buhler, L.

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N2 - Pressure-driven magnetohydrodynamic duct flow in a transverse uniform magnetic field is studied by direct numerical simulation. The electric boundary conditions correspond to Hunt's flow with perfectly insulating walls parallel to the magnetic field (sidewalls) and perfectly conducting walls perpendicular to the magnetic field (Hartmann walls). The velocity distribution exhibits strong jets at the sidewalls, which are susceptible to instability even at low Reynolds numbers Re. We explore the onset of time-dependent flow and transition to states with evolved turbulence for a moderate Hartmann number $Ha = 100$ . At low Re time-dependence appears in the form of elongated Ting-Walker vortices at the sidewalls of the duct, which, upon increasing Re, develop into more complex structures with higher energy and then the sidewall jets partially detach from the walls. At high values of Re jet detachments disappear and the flow consists of two turbulent jets and nearly laminar core. It is also demonstrated that, there is a range of Re, where Hunt's flow exhibits a pronounced hysteresis behavior, so that different unsteady states can be observed for the same flow parameters. In this range multiple states may develop and co-exist, depending on the initial conditions.

AB - Pressure-driven magnetohydrodynamic duct flow in a transverse uniform magnetic field is studied by direct numerical simulation. The electric boundary conditions correspond to Hunt's flow with perfectly insulating walls parallel to the magnetic field (sidewalls) and perfectly conducting walls perpendicular to the magnetic field (Hartmann walls). The velocity distribution exhibits strong jets at the sidewalls, which are susceptible to instability even at low Reynolds numbers Re. We explore the onset of time-dependent flow and transition to states with evolved turbulence for a moderate Hartmann number $Ha = 100$ . At low Re time-dependence appears in the form of elongated Ting-Walker vortices at the sidewalls of the duct, which, upon increasing Re, develop into more complex structures with higher energy and then the sidewall jets partially detach from the walls. At high values of Re jet detachments disappear and the flow consists of two turbulent jets and nearly laminar core. It is also demonstrated that, there is a range of Re, where Hunt's flow exhibits a pronounced hysteresis behavior, so that different unsteady states can be observed for the same flow parameters. In this range multiple states may develop and co-exist, depending on the initial conditions.

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DO - 10.1209/0295-5075/115/44002

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