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1. Decay of turbulence in a liquid metal duct flow with transverse magnetic field

   https://doi.org/10.1017/jfm.2019.171  

   Zikanov, Oleg; Krasnov, Dmitry; Boeck, Thomas; Sukoriansky, Semion (May 2019, Journal of Fluid Mechanics)

   Decay of honeycomb-generated turbulence in a duct with a static transverse magnetic field is studied via direct numerical simulations. The simulations follow the revealing experimental study of Sukoriansky et al.  ( Exp. Fluids , vol. 4 (1), 1986, pp. 11–16), in particular the paradoxical observation of high-amplitude velocity fluctuations, which exist in the downstream portion of the flow when the strong transverse magnetic field is imposed in the entire duct including the honeycomb exit, but not in other configurations. It is shown that the fluctuations are caused by the large-scale quasi-two-dimensional structures forming in the flow at the initial stages of the decay and surviving the magnetic suppression. Statistical turbulence properties, such as the energy decay curves, two-point correlations and typical length scales are computed. The study demonstrates that turbulence decay in the presence of a magnetic field is a complex phenomenon critically depending on the state of the flow at the moment the field is introduced. 

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2. Liquid metal swirling flow affected by transverse magnetic field

   https://doi.org/10.22364/mhd.56.2-3.3  

   Krasnov, D.; Kolesnikov, Yu. B.; Belyaev, I. A.; Listratov, Ya. I.; Zikanov, O. (September 2020, Magnetohydrodynamics)

   null (Ed.)

   In this work we study numerically liquid metal flow in a square duct under the influence of a transverse magnetic field applied in a spanwise direction (coplanar). The key interest of the present study is an attempt of passive control of flow regimes developed under magnetic field and thermal loads by applying specially shaped conditions, such as swirling, at the duct inlet. In this paper, we report results of numerical simulations of the interaction of swirling flow and transverse magnetic field in a square duct flow. Analysis of the obtained regimes might be important for the development of an experimental setup, in order to design corresponding inlet sections. 

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3. Magnetoconvection in a horizontal duct flow at very high Hartmann and Grashof numbers

   https://doi.org/10.1017/jfm.2021.987  

   Akhmedagaev, R.; Zikanov, O.; Listratov, Y. (January 2022, Journal of Fluid Mechanics)

   Direct numerical simulations and linear stability analysis are carried out to study mixed convection in a horizontal duct with constant-rate heating applied at the bottom and an imposed transverse horizontal magnetic field. A two-dimensional approximation corresponding to the asymptotic limit of a very strong magnetic field effect is validated and applied, together with full three-dimensional analysis, to investigate the flow's behaviour in the previously unexplored range of control parameters corresponding to typical conditions of a liquid metal blanket of a nuclear fusion reactor (Hartmann numbers up to $10^4$ and Grashof numbers up to $$10^{10}$$ ). It is found that the instability to quasi-two-dimensional rolls parallel to the magnetic field discovered at smaller Hartmann and Grashof numbers in earlier studies also occurs in this parameter range. Transport of the rolls by the mean flow leads to magnetoconvective temperature fluctuations of exceptionally high amplitudes. It is also demonstrated that quasi-two-dimensional structure of flows at very high Hartmann numbers does not guarantee accuracy of the classical two-dimensional approximation. The accuracy deteriorates at the highest Grashof numbers considered in the study. 

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4. Inverse cascade from helical and non-helical decaying columnar magnetic fields

   https://doi.org/10.1017/s0022377825100664  

   Brandenburg, Axel; Yi, Longqing; Wu, Xianshu (August 2025, Journal of Plasma Physics)

   Powerful lasers may be used in the future to produce magnetic fields that would allow us to study turbulent magnetohydrodynamic inverse cascade behaviour. This has so far only been seen in numerical simulations. In the laboratory, however, the produced fields may be highly anisotropic. Here, we present corresponding simulations to show that, during the turbulent decay, such a magnetic field undergoes spontaneous isotropisation. As a consequence, we find the decay dynamics to be similar to that in isotropic turbulence. We also find that an initially pointwise non-helical magnetic field is unstable and develops magnetic helicity fluctuations that can be quantified by the Hosking integral. It is a conserved quantity that characterises magnetic helicity fluctuations and governs the turbulent decay when the mean magnetic helicity vanishes. As in earlier work, the ratio of the magnetic decay time to the Alfvén time is found to be approximately$$50$$in the helical and non-helical cases. At intermediate times, the ratio can even reach a hundred. This ratio determines the endpoints of cosmological magnetic field evolution. 

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5. MHD Turbulent Power Anisotropy in the Inner Heliosphere

   https://doi.org/10.3847/1538-4357/ac70cb  

   Adhikari, L.; Zank, G. P.; Zhao, L.-L.; Telloni, D. (July 2022, The Astrophysical Journal)

   Abstract We study anisotropic magnetohydrodynamic (MHD) turbulence in the slow solar wind measured by Parker Solar Probe (PSP) and Solar Orbiter (SolO) during its first orbit from the perspective of variance anisotropy and correlation anisotropy. We use the Belcher & Davis approach (M1) and a new method (M2) that decomposes a fluctuating vector into parallel and perpendicular fluctuating vectors. M1 and M2 calculate the transverse and parallel turbulence components relative to the mean magnetic field direction. The parallel turbulence component is regarded as compressible turbulence, and the transverse turbulence component as incompressible turbulence, which can be either Alfvénic or 2D. The transverse turbulence energy is calculated from M1 and M2, and the transverse correlation length from M2. We obtain the 2D and slab turbulence energy and the corresponding correlation lengths from those transverse turbulence components that satisfy an angle between the mean solar wind flow speed and mean magnetic field θ UB of either (i) 65° < θ UB < 115° or (ii) 0° < θ UB < 25° (155° < θ UB < 180°), respectively. We find that the 2D turbulence component is not typically observed by PSP near perihelion, but the 2D component dominates turbulence in the inner heliosphere. We compare the detailed theoretical results of a nearly incompressible MHD turbulence transport model with the observed results of PSP and SolO measurements, finding good agreement between them. 

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