Instabilities in Mixed Convection at Moderate and Strong Magnetic Fields

• Applicant: Dr. Dmitry Krasnov
• Subject Area: Fluid Mechanics ; Energy Process Engineering
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 388404029

• Final Report Year: 2024

Final Report Abstract

Magnetohydrodynamic (MHD) flows of liquid metals, subjected to strong influence of magneto- and thermogravitational effects, play a key role in the blankets, designed for tokamak fusion reactors. The existing cooling blanket systems are represented by two major types: solid state and liquid metal blankets. In this project we have focused on liquid metal blankets, they are typically seen as a preferred option by providing higher thermal and breeding efficiency. However, the use of liquid metals is not free from problems. There are two very important aspects, relevant to the operating conditions: the extremely strong magnetic fields and very strong heat flux imposed by radiation from the plasma and by neutron absorption. These conditions are prone to develop large-scale instabilities and irregular thermal fluctuations. Thus, understanding the behavior of liquid metal flows at extreme parameters becomes an important and non-trivial task. This task can be advanced with laboratory experiments and numerical simulations performed for simplified configurations, e.g., duct or pipe geometries. In this project we have addressed the physical phenomena relevant to thermogravitational convection and MHD flows in rectangular ducts. We have used a combination of (i) fully 3D numerical models applied for the analysis of idealized configurations and (ii) high-fidelity experiments representing more realistic settings. We have determined the conditions (parameter ranges) leading to the unsteady structures, studied the effects of intrinsic symmetry of the system, and analyzed the implications for heat transfer and temperature distribution. Also we have considered the possibility of introducing control tools, such as inlet swirling and vortex promoters, to minimise the negative effects of thermal fluctuations and enhance heat and mass transfer. As a summarizing thought, our findings suggest that the large-scale fluctuations in magneto-convection cannot be fully avoided. Instead, they can be induced and sustained in predictive and controlled manner with the help of control tools, which have, ultimately, boosted the integral heat transfer by many factors.

Publications

• “Heating nonuniformity influence on the liquid metal flow characteristics in the presence of a magnetic field during mixed convection in a duct”. In: VANT 5 (2018). (in Russian), pp. 86–95.
  I. Belyaev, N. Razuvanov, D. Krasnov & V. Sviridov
  
• Decay of turbulence in a liquid metal duct flow with transverse magnetic field. Journal of Fluid Mechanics, 867, 661-690.
  Zikanov, Oleg; Krasnov, Dmitry; Boeck, Thomas & Sukoriansky, Semion
  
• “Flow swirling in strong transverse magnetic field”. In: 2nd International Conference ”Problems of Thermonuclear Energy and Plasma Technology”. Moscow, Russia, 2019.
  D. Krasnov, I. Belyaev, D. Biryukov, Y. Listratov, Y. Kolesnikov, O. Zikanov & V. Sviridov
  
• “Instabilities in mixed convection at moderate and strong magnetic fields”. In: Proceedings of the 11th PAMIR International Conference Fundamental and Applied MHD. Reims, France, 2019, pp. 82–86.
  I. Belyaev, D. Krasnov, D. Biryukov, Y. Listratov, Y. Kolesnikov, O. Zikanov & V. Sviridov
  
• “Turbulent Rayleigh-Benard convection in strong vertical magnetic field”. In: 2nd International Conference ”Problems of Thermonuclear Energy and Plasma Technology”. Moscow, Russia, 2019.
  Akhmedagaev, R.; Zikanov, O.; Krasnov, D. & Schumacher, J.
  
• “Turbulent Rayleigh-Benard convection in strong vertical magnetic field”. In: Proceedings of the 11th PAMIR International Conference Fundamental and Applied MHD. Reims, France, 2019, pp. 157–161.
  Akhmedagaev, R.; Zikanov, O.; Krasnov, D. & Schumacher, J.
  
• Effects of symmetry on magnetohydrodynamic mixed convection flow in a vertical duct. Physics of Fluids, 32(9).
  Belyaev, Ivan; Krasnov, Dmitry; Kolesnikov, Yuri; Biryukov, Dmitry; Chernysh, Denis; Zikanov, Oleg & Listratov, Yaroslav
  
• Liquid metal swirling flow affected by transverse magnetic field. Magnetohydrodynamics, 56(2-3), 121-130.
  D. Krasnov; Y. Kolesnikov; I. Belyaev; Y. Listratov & O. Zikanov
  
• Rayleigh--Bénard convection in strong vertical magnetic field: flow structure and verification of numerical method. Magnetohydrodynamics, 56(2-3), 157-166.
  R. Akhmedagaev; O. Zikanov; D. Krasnov & J. Schumacher
  
• Turbulent Rayleigh–Bénard convection in a strong vertical magnetic field. Journal of Fluid Mechanics, 895.
  Akhmedagaev, R.; Zikanov, O.; Krasnov, D. & Schumacher, J.
  
• Transformation of a submerged flat jet under strong transverse magnetic field. EPL (Europhysics Letters), 134(2), 24003.
  Krasnov, D.; Listratov, Ya.; Kolesnikov, Yu.; Belyaev, I.; Pyatnitskaya, N.; Sviridov, E. & Zikanov, O.
  
• Convective mesoscale turbulence at very low Prandtl numbers. Journal of Fluid Mechanics, 948.
  Pandey, Ambrish; Krasnov, Dmitry; Sreenivasan, Katepalli R. & Schumacher, Jörg
  
• Similarities between characteristics of convective turbulence in confined and extended domains. Physica D: Nonlinear Phenomena, 442, 133537.
  Pandey, Ambrish; Krasnov, Dmitry; Schumacher, Jörg; Samtaney, Ravi & Sreenivasan, Katepalli R.
  
• “Experimental study of submerged liquid metal jet in a rectangular duct in a transverse magnetic field”. In: J. Fluid Mech. 953 (2022), A10.
  I. Belyaev, I. Mironov, N. Luchinkin, Y. Listratov, Y. Kolesnikov, D. Krasnov, O. Zikanov & S. Molokov
  
• MHD flow of submerged jets behind the inlet disturbance. PAMM, 22(1).
  Krasnov, Dmitry; Listratov, Yaroslav; Belyaev, Ivan; Kolesnikov, Yuri; Sviridov, Evgeny & Zikanov, Oleg
  
• “Inlet flow formation for passive control of magneto-hydrodynamic liquid metal flow in a duct”. In: J. High Temperature (2023). Accepted for publication
  I. Belyaev, D. Chernysh, N. Luchinkin, D. Krasnov, Y. Kolesnikov & Y. Listratov
  
• “Tensor-product-Thomas elliptic solver for liquid-metal magnetohydrodynamics”. In: J. Comput. Phys. 474 (2023), p. 111784
  D. Krasnov, A. Akhtari, J. Schumacher & O. Zikanov