Limits of strong magneto-convective fluctuations in liquid metal flow in a heated vertical pipe affected by a transverse magnetic field
Limits of strong magneto-convective fluctuations in liquid metal flow in a heated vertical pipe affected by a transverse magnetic field
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横向磁场作用下加热立管内液态金属流强磁对流脉动的极限
DOI：
10.1016/j.ijthermalsci.2020.106773
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发表时间：
2021
影响因子：
4.5
通讯作者：
P. Frick
中科院分区：
文献类型：
--
作者：
I. Belyaev;P. Sardov;I. Melnikov;P. Frick
从实验和数值研究中已知，在液态金属的通道流动中，由温度梯度提供的强浮力在磁场特定结构中产生，所述磁场特定结构以大尺度磁对流波动（MCF）的形式表现出来，伴随着异常大幅度的温度波动。MCFs的具体结构取决于液态金属的性质，取决于通道配置及其对重力和磁场的取向，以及取决于流动的控制参数的组合。在这项工作中，我们第一次尝试在参数空间中定义一个特定配置的加热磁流体动力学（MHD）流的MCFs的存在域。本文对横向磁场中单侧加热管中汞的向下流动进行了实验研究，这可以看作是托卡马克包层模块中通道的一级近似。我们发现，对于这种配置，弱浮力极限由临界Richardson数Ri m i n 0定义。08，其指示所需浮力的值，该浮力应足够强以在MCF中表现出自身。弱磁场极限由临界斯图尔特数N m i n 1定义。5，其指示影响产生的湍流并提供从均匀湍流到MCF的过渡的所需磁场的值。高磁场极限，其确定由强磁场抑制的MF的边界，取决于流速和加热速率，并且在通过哈特曼层厚度定义的雷诺数Rh方面具有更清晰的配置。在中等理查森数下，边界由Ri= 6/Rh线限制。随着Ri的进一步增加，边界线更加陡峭地上升，并趋向于绝对上限Rh− 1= 2/25，在该绝对上限以上，磁场对于任何浮力都使流动完全分层。我们已经表明，MCF强烈影响热传输，能够从根本上增强它。
It is known from experimental and numerical studies that in channel flows of liquid metals, strong buoyancy forces, provided by temperature gradients, generate in magnetic field specific structures, which manifest themselves in the form of large-scale magneto-convective fluctuations (MCFs), accompanied by temperature fluctuations of anomalously large amplitude. The specific structure of MCFs depends on the properties of the liquid metal, on the channel configuration and its orientation to gravity and to the magnetic field, and on the combination of governing parameters of the flow. In this work we made the first attempt to define the domain of existence of MCFs in the parameter space for one specific configuration of the heated magnetohydrodynamic (MHD) flow. We studied experimentally a downward flow of mercury in the one-sided heated pipe in a transverse magnetic field, which can be considered as a first approximation to channels within a blanket module of a tokamak. We found that for this configuration, the weak buoyancy limit is defined by the critical Richardson number Ri m i n≈ 0. 08, which indicates the value of required buoyancy, which should be strong enough to manifest itself in MCFs. The weak magnetic field limit is defined by the critical Stuart number N m i n≈ 1. 5, which indicates the value of the required magnetic field that affects the developed turbulence and provides the transition from homogeneous turbulence to MCFs. The high magnetic field limit, which determines the boundary of MFs suppression by a strong magnetic field, depends on the flow rate and on the heating rate and has a clearer configuration in terms of a Reynolds number Rh, defined through the Hartmann layer thickness. At moderate Richardson numbers, the boundary is confined by a line Ri= 6/Rh. With further increase of Ri, the border line rises more steeply and tends to an absolute upper limit Rh− 1= 2/25, above which the magnetic field completely laminarizes the flow for any buoyancy forces. We have shown, that MCFs strongly affect the heat transport, being able to essentially enhance it.
影响因子：
4.6
作者：
I. Belyaev;D. Krasnov;Y. Kolesnikov;D. Biryukov;D. Chernysh;O. Zikanov;Y. Listratov
通讯作者：
I. Belyaev;D. Krasnov;Y. Kolesnikov;D. Biryukov;D. Chernysh;O. Zikanov;Y. Listratov