Article
Mechanics
Bin Jiang, Cheng Li, Yan Yang, Kangcheng Zhou, William H. Matthaeus, Minping Wan
Summary: In the presence of anisotropy, the widespread use of the isotropic form of the third-order law to estimate energy transfer rates is questionable. On the other hand, the direction-averaged third-order structure function properly accounts for the effect of anisotropy and accurately predicts the energy transfer rates and inertial range.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Jean-Mathieu Teissier, Wolf-Christian Mueller
Summary: This study investigates the inverse transfer of magnetic helicity in large-scale mechanically driven turbulent flows using direct numerical simulations in the ideal magnetohydrodynamics framework. It is found that compressibility leads to smaller absolute values of magnetic helicity scaling exponents, and strong deviations are visible in compressively driven turbulence even at relatively low Mach numbers.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Jean-Mathieu Teissier, Wolf-Christian Mueller
Summary: Through Fourier shell-to-shell transfer analysis, the role of different helical components of magnetic and velocity fields in the inverse spectral transfer of magnetic helicity was investigated. Three physical phenomena were distinguished in the spectral transfer of magnetic helicity: local inverse transfer, non-local inverse transfer, and local direct transfer.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Yan Yang, Minping Wan, William H. Matthaeus, Shiyi Chen
Summary: In studies of compressible magnetohydrodynamic (MHD) turbulence, it was found that compressive kinetic and thermal energy exchange is driven by acoustic waves through pressure dilatation, while exchange between kinetic and magnetic energy is dominated by interactions involving solenoidal velocity. Systematic rapid adjustments were found to be reproducible with simple scalings derived from empirical data.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
J. Pratt, A. Busse, W-C Mueller
Summary: This study investigates the influence of a magnetic field on anisotropic magnetohydrodynamic (MHD) turbulence using direct numerical simulations. The results show that the diffusion curves of single particles exhibit mildly superdiffusive behaviors in different directions. The dispersion of particle pairs is affected by competing alignment processes, especially at the beginning of the inertial subrange. The observed scaling for relative dispersion is steeper than the Richardson prediction, particularly at larger Reynolds numbers.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Santiago J. Benavides, Keaton J. Burns, Basile Gallet, James Y-K. Cho, Glenn R. Flierl
Summary: The study numerically investigates three-dimensional magnetohydrodynamic turbulence affected by the competing effects of rotation and a background magnetic field. It finds that increasing the rotation rate leads to significant changes in the turbulent flow structure in the presence of a strong background field, and identifies distinct values where the transitions occur.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Long Chen, Alban Potherat, Ming-Jiu Ni, Rene Moreau
Summary: High-resolution direct numerical simulations were conducted to study turbulent shear flow of liquid metal in a cylindrical container driven by an azimuthal Lorentz force. The simulations accurately reproduced experimental findings and revealed a transition to small scale turbulence at certain Reynolds numbers. The study also confirmed theoretical laws for cutoff scale and characteristics of sheared magnetohydrodynamics (MHD) turbulence.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Astronomy & Astrophysics
Andrew Hillier, Ben Snow, Inigo Arregui
Summary: In many astrophysical systems, the mixing between cool and hot temperature gas/plasma creates an intermediate temperature phase with increased radiative losses, driving efficient cooling. This paper derives equations to model the evolution of this mixing layer, and predicts the cooling rate and the rate of condensation of coronal material due to mixing. These predictions are compared to simulations and applied to prominence threads and spicules, showing that the mixing process can explain the warm emission observed without the need for additional heating.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Pallavi Bhat
Summary: This study used periodic box DNS to simulate large-scale dynamos formed by helically forced turbulence, finding that in the case of anisotropic forcing, the non-linear behavior of the large-scale dynamo is weakly dependent on the magnetic Reynolds number. The evolution of magnetic helicity in the anisotropic case is distinctly different from that in the isotropic case, which may hold promise for addressing important issues such as catastrophic quenching.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Mechanics
Krzysztof A. Mizerski
Summary: The magnetohydrodynamic (MHD) turbulence is present in both engineering laboratory flows and natural systems. It has the ability to generate and sustain large-scale and small-scale magnetic fields, playing a crucial role in processes such as nuclear fusion energy production. The turbulence also enhances large-scale diffusion and affects the energy and helicity spectra of strongly turbulent flows.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Souvik Naskar, Anikesh Pal
Summary: This study investigates rapidly rotating convection-driven dynamos under different boundary conditions using direct numerical simulations. The results show that the statistical behavior of the dynamos, including force balance, energetics, and heat transport, depends on the boundary conditions, especially the velocity and magnetic boundary conditions. The study also finds that heat transfer is enhanced in rotating dynamo convection compared to non-magnetic rotating convection, with the peak enhancement occurring at specific boundary conditions.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Fluids & Plasmas
Forrest W. Glines, Philipp Grete, Brian W. O'Shea
Summary: Research shows that regardless of the initial magnetic field strength, magnetic energy becomes dominant over all scales after several dynamical times, while the spectral indices of kinetic and magnetic energy flatten over time. Magnetic fields facilitate a significant amount of energy flux and suppress kinetic energy cascade, leading to nonlocal energy transfer from large-scale kinetic energy to intermediate and small-scale magnetic energy via magnetic tension.
Article
Astronomy & Astrophysics
Pallavi Bhat, Muni Zhou, Nuno F. Loureiro
Summary: Recent numerical studies have shown the existence of inverse transfer of magnetic energy in 3D magnetically dominated turbulence, likely driven by magnetic reconnection. The scaling behavior is found to be similar between 2D and 3D cases. Furthermore, simulations also demonstrate an inverse transfer of magnetic energy in 3D when the magnetic field is subdominant to the flow, with the emergence of a dynamo effect.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Multidisciplinary Sciences
Thomas Howson
Summary: Oscillatory power and MHD waves in the solar corona have attracted great interest in the context of coronal heating problem. However, uncertainties remain in estimating their energy flux and their contribution to the coronal energy budget. The dissipations of wave energy and the generation of small-scale heating are important issues. MHD turbulence has been shown to efficiently dissipate large quantities of energy and drive complex turbulent behavior in the solar corona.
Article
Astronomy & Astrophysics
L. Adhikari, G. P. Zank, L-L Zhao, M. Nakanotani, S. Tasnim
Summary: The study developed a theoretical model combining nearly incompressible magnetohydrodynamic (NI MHD) turbulence with a solar wind model that includes electron pressure and heat flux. The results show that the model is consistent with the measurements of fast solar wind by PSP and Helios 2.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Mechanics
R. Akhmedagaev, O. Zikanov, D. Krasnov, J. Schumacher
JOURNAL OF FLUID MECHANICS
(2020)
Article
Mechanics
Ivan Belyaev, Dmitry Krasnov, Yuri Kolesnikov, Dmitry Biryukov, Denis Chernysh, Oleg Zikanov, Yaroslav Listratov
Review
Mechanics
Oleg Zikanov, Ivan Belyaev, Yaroslav Listratov, Peter Frick, Nikita Razuvanov, Valentin Sviridov
Summary: An imposed strong magnetic field can suppress turbulence and alter the flow of an electrically conducting fluid, such as in the case of mixed convection flows in pipes and ducts. This has implications for the design of liquid-metal components in future nuclear fusion reactors. The review outlines the recent studies on flow transformation, highlighting key facts and open questions in this area, as well as discussing implications for fusion reactor technology and novel methods.
APPLIED MECHANICS REVIEWS
(2021)
Article
Thermodynamics
Linyan Xiang, Cheol W. Lee, Oleg Zikanov, Chih-Cheng Hsu
Summary: This paper introduces a method to overcome the high computational cost of CFD modeling by using reduced-order models to accurately predict the thermal behavior of thermal management systems for battery packs of electrical/hybrid electric vehicles. By using projection onto the Krylov subspace, algorithms for developing reduced-order models for both single-input and multiple-input cases are presented. The reduced-order models are validated through comparison with full-order CFD simulations, showing a reduction in computational time by approximately 10^3 without significant loss of accuracy.
APPLIED THERMAL ENGINEERING
(2022)
Article
Energy & Fuels
Chiara Mistrangelo, Leo Buehler, Ciro Alberghi, Serena Bassini, Luigi Candido, Cyril Courtessole, Alessandro Tassone, Fernando R. Urgorri, Oleg Zikanov
Summary: The European design strategy has identified mature concepts for DEMO breeding blankets that require reduced technological extrapolation and testing in ITER. Understanding magnetohydrodynamic interactions and other physical phenomena in liquid metal blankets is crucial for optimizing test blanket module designs. Both numerical and experimental approaches are being discussed to reliably predict processes in liquid metal blankets.
Article
Mechanics
R. Akhmedagaev, O. Zikanov, Y. Listratov
Summary: The study investigates mixed convection in a horizontal duct with a horizontal magnetic field and constant-rate heating, finding that instability to quasi-two-dimensional rolls parallel to the magnetic field occurs in the previously unexplored range of control parameters for liquid metal blankets of nuclear fusion reactors. The transport of the rolls leads to exceptionally high amplitude magnetoconvective temperature fluctuations, and a quasi-two-dimensional flow structure at very high Hartmann numbers does not guarantee the accuracy of the classical two-dimensional approximation, deteriorating at the highest Grashof numbers considered in the study.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Computer Science, Interdisciplinary Applications
Dmitry Krasnov, Ali Akhtari, Oleg Zikanov, Jorg Schumacher
Summary: A new approach combining conservative finite-difference discretization with a tensor-product-Thomas solution is proposed for numerical simulation of magnetohydrodynamic flows of liquid metals. The method efficiently solves the important elliptic problems for electric potential in flow domains with thin electrically conducting walls. Its effectiveness is demonstrated through benchmark problems and compared favorably to existing methods in terms of computational efficiency. (c) 2022 Elsevier Inc. All rights reserved.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Mechanics
Ivan A. A. Belyaev, Ivan S. S. Mironov, Nikita A. A. Luchinkin, Yaroslav I. I. Listratov, Yuri B. B. Kolesnikov, Dmitry Kransov, Oleg Zikanov, Sergei Molokov
Summary: This study experimentally investigates the dynamics of a liquid metal flow in the form of a submerged round jet entering a square duct in the presence of a transverse magnetic field. The results show that the instability of the jet leads to high-amplitude fluctuations, and the flow structure and fluctuation properties are determined by the value of the Stuart number.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Linyan Xiang, Cheol W. Lee, Oleg Zikanov, Mohamed Abuhegazy, Svetlana V. Poroseva
Summary: A new approach to numerical modeling of airborne transmission of respiratory infections in indoor environments is presented in this paper. The approach is based on the Eulerian description of the aerosol field and uses reduced-order modeling (ROM) to reduce computational cost. The ROM is validated through direct comparison with full-order computational fluid dynamics (CFD) solutions and Lagrangian tracking data. Computational tests show that the ROM reduces computational cost by a factor of about 10³ without significant loss in accuracy.
Article
Computer Science, Artificial Intelligence
Zhuo Wang, Wenhua Yang, Linyan Xiang, Xiao Wang, Yingjie Zhao, Yaohong Xiao, Pengwei Liu, Yucheng Liu, Mihaela Banu, Oleg Zikanov, Lei Chen
Summary: The article introduces a simple yet powerful multi-input convolutional network model called yNet, which can quickly simulate various field evolutions and accurately extrapolate predictions in terms of temporal ranges, spatial domains, and geometrical shapes.
Article
Physics, Multidisciplinary
D. Krasnov, Ya Listratov, Yu Kolesnikov, I Belyaev, N. Pyatnitskaya, E. Sviridov, O. Zikanov
Summary: In this study, the flow generated by a planar jet at the inlet of a duct and influenced by a perpendicular magnetic field was analyzed through high-resolution numerical simulations at very high Reynolds and Hartmann numbers. The flow structure in the inlet area was found to be significantly altered, with the emergence of three new planar jets along the magnetic field lines. The downstream evolution of the flow involves the Kelvin-Helmholtz instability of the jets and a slow decay of the resulting quasi-two-dimensional turbulence.
Article
Mechanics
I. A. Belyaev, N. Yu Pyatnitskaya, N. A. Luchinkin, D. Krasnov, Yu B. Kolesnikov, Ya Listratov, I. S. Mironov, O. Zikanov, E. Sviridov
Summary: This study experimentally investigates a liquid metal flat jet in a square duct under the influence of a transverse magnetic field, considering cases where the applied magnetic field is oriented parallel or perpendicular to the initial plane of the jet. By measuring signals of streamwise velocity at different locations, the study aims to determine average velocity profiles and spatial-temporal characteristics of the velocity field, comparing two configurations under the same flow regimes and equipment.
MAGNETOHYDRODYNAMICS
(2021)
Article
Mechanics
D. Krasnov, Yu B. Kolesnikov, I. A. Belyaev, Ya Listratov, O. Zikanov
MAGNETOHYDRODYNAMICS
(2020)
Article
Mechanics
R. Akhmedagaev, O. Zikanov, D. Krasnov, J. Schumacher
MAGNETOHYDRODYNAMICS
(2020)
Proceedings Paper
Engineering, Mechanical
Oleg Zikanov, Dmitry Krasnov, Thomas Boeck, Semion Sukoriansky
PROCEEDINGE OF THE ASME/JSME/KSME JOINT FLUIDS ENGINEERING CONFERENCE, 2019, VOL 1
(2019)