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

   Zikanov, O. (July 2019, Fundamental and Applied MHD, 11th PAMIR international conference)

   Decay of honeycomb-generated turbulence in a duct with a static transverse magnetic field is studied via high-resolution direct numerical simulations. The simulations follow the experimental study [1], 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. 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. On the Effect of Driving Turbulent-like Fluctuations on a Harris Current Sheet Configuration and the Formation of Plasmoids

   https://doi.org/10.3847/1538-4357/ad5e73  

   Agudelo_Rueda, Jeffersson_A; Liu, Yi-Hsin; Germaschewski, Kai; Hesse, Michael; Bessho, Naoki (August 2024, The Astrophysical Journal)

   Abstract Energy dissipation in collisionless plasmas is one of the most outstanding open questions in plasma physics. Magnetic reconnection and turbulence are two phenomena that can produce the conditions for energy dissipation. These two phenomena are closely related to each other in a wide range of plasmas. Turbulent fluctuations can emerge in critical regions of reconnection events, and magnetic reconnection can occur as a product of the turbulent cascade. In this study, we perform 2D particle-in-cell simulations of a reconnecting Harris current sheet in the presence of turbulent fluctuations to explore the effect of turbulence on the reconnection process in collisionless nonrelativistic pair plasmas. We find that the presence of a turbulent field can affect the onset and evolution of magnetic reconnection. Moreover, we observe the existence of a scale-dependent amplitude of magnetic field fluctuations above which these fluctuations are able to disrupt the growing of magnetic islands. These fluctuations provide thermal energy to the particles within the current sheet and preferential perpendicular thermal energy to the background population. 

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