Turbulent drag reduction in magnetohydrodynamic and quasi-static magnetohydrodynamic turbulence

Verma, Mahendra K.; Alam, Shadab; Chatterjee, Soumyadeep

doi:10.1063/1.5142294

Cited by 9 publications

(11 citation statements)

References 61 publications

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“…For example, in decaying MHD turbulence, magnetic field feeds energy to the velocity field when b 2 u 2 and vice versa [152]. The cross energy transfer Π u< ζ (k) is also responsible for the drag reduction in MHD turbulence [43]. Since Π u< ζ (k) > 0, using Eq.…”

Section: Various Energy Fluxes Of Mhd Turbulencementioning

confidence: 99%

Variable energy flux in turbulence

Verma¹

2021

J. Phys. A: Math. Theor.

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In three-dimensional hydrodynamic turbulence forced at large length scales, a constant energy flux $ \Pi_u $ flows from large scales to intermediate scales, and then to small scales. It is well known that for multiscale energy injection and dissipation, the energy flux $\Pi_u$ varies with scales. In this review we describe this principle and show how this general framework is useful for describing a variety of turbulent phenomena. Compared to Kolmogorov's spectrum, the energy spectrum steepens in turbulence involving quasi-static magnetofluid, Ekman friction, stable stratification, magnetohydrodynamics, and solution with dilute polymer. However, in turbulent thermal convection, in unstably stratified turbulence such as Rayleigh-Taylor turbulence, and in shear turbulence, the energy spectrum has an opposite behaviour due to an increase of energy flux with wavenumber. In addition, we briefly describe the role of variable energy flux in quantum turbulence, in binary-fluid turbulence including time-dependent Landau-Ginzburg and Cahn-Hillianrd equations, and in Euler turbulence. We also discuss energy transfers in anisotropic turbulence.

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Section: Various Energy Fluxes Of Mhd Turbulencementioning

confidence: 99%

Variable energy flux in turbulence

Verma¹

2021

J. Phys. A: Math. Theor.

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“…Note that the kinetic energy spectrum, ∼k −0.73 , is steeper than the magnetic energy spectrum, ∼k −0.68 . This differential can be attributed to the energy transfer from the velocity field to the magnetic field [7]. We have compared our results with those from the past, e.g., observational works on solar wind [25,26] and numerical works [57][58][59][60].…”

Section: Numerical Results On the Energy Fluxesmentioning

confidence: 87%

“…In 3D hydrodynamic turbulence, the kinetic energy flux Π u < u > remains constant in inertial range and it is equal to the kinetic energy dissipation rate. This flux, however, is not constant in MHD turbulence [7]. However, the total energy transferred to the inertial range of the velocity field is dissipated by the viscous force.…”

Section: Energy Fluxes and Exact Relationsmentioning

confidence: 99%

“…Due to the energy exchange between the velocity and magnetic fields, the energy flux for the velocity field is no longer constant. Verma et al [7] showed that in a typical turbulent magnetofluid, the inertial-range kinetic energy flux is depleted due to the energy transfer from the velocity to the magnetic field. The magnetic energy flux also exhibits variability due to these transfers.…”

Section: Introductionmentioning

confidence: 99%

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Variable Energy Fluxes and Exact Relations in Magnetohydrodynamics Turbulence

Verma

Sharma

Chatterjee

et al. 2021

Fluids

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In magnetohydrodynamics (MHD), there is a transfer of energy from the velocity field to the magnetic field in the inertial range itself. As a result, the inertial-range energy fluxes of velocity and magnetic fields exhibit significant variations. Still, these variable energy fluxes satisfy several exact relations due to conservation of energy. In this paper, using numerical simulations, we quantify the variable energy fluxes of MHD turbulence, as well as verify several exact relations. We also study the energy fluxes of Elsässer variables that are constant in the inertial range.

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“…Selfconsistent simulations extended to larger distances may tell us why only specific values of the drag coefficient C D and snowplow efficiency C S seemed applicable to the observed flow patterns. Also, some of our assumptions about geometric inertia effects (i.e., C A ) and even the quadratic nature of the drag may need to be revised in the light of new simulations (see, e.g., Maloney & Gallagher 2010;Verma et al 2020).…”

Section: Observational Constraints On Initial Conditionsmentioning

confidence: 99%

Inward Propagating Plasma Parcels in the Solar Corona: Models with Aerodynamic Drag, Ablation, and Snowplow Accretion

Cranmer,

DeForest,

Gibson

2021

Preprint

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Although the solar wind flows primarily outward from the Sun to interplanetary space, there are times when small-scale plasma inflows are observed. Inward-propagating density fluctuations in polar coronal holes were detected by the COR2 coronagraph on board the STEREO-A spacecraft at heliocentric distances of 7 to 12 solar radii, and these fluctuations appear to undergo substantial deceleration as they move closer to the Sun. Models of linear magnetohydrodynamic waves have not been able to explain these deceleration patterns, so they have been interpreted more recently as jets from coronal sites of magnetic reconnection. In this paper, we develop a range of dynamical models of discrete plasma parcels with the goal of better understanding the observed deceleration trend. We found that parcels with a constant mass do not behave like the observed flows, and neither do parcels undergoing ablative mass loss. However, parcels that accrete mass in a snowplow-like fashion can become decelerated as observed. We also extrapolated OMNI in situ data down to the so-called Alfvén surface and found that the initial launch-point for the observed parcels may often be above this critical radius. In other words, in order for the parcels to flow back down to the Sun, their initial speeds are probably somewhat nonlinear (i.e., supra-Alfvénic) and thus the parcels may be associated with structures such as shocks, jets, or shear instabilities.

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Turbulent drag reduction in magnetohydrodynamic and quasi-static magnetohydrodynamic turbulence

Cited by 9 publications

References 61 publications

Variable energy flux in turbulence

Variable energy flux in turbulence

Variable Energy Fluxes and Exact Relations in Magnetohydrodynamics Turbulence

Inward Propagating Plasma Parcels in the Solar Corona: Models with Aerodynamic Drag, Ablation, and Snowplow Accretion

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