Study of natural convection in a heated cavity with magnetic fields normal to the main circulation
Study of natural convection in a heated cavity with magnetic fields normal to the main circulation
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DOI：
10.1016/j.ijheatmasstransfer.2018.06.019
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发表时间：
2018-12
影响因子：
5.2
通讯作者：
Long Chen;Bai-Qi Liu;M. Ni
中科院分区：
文献类型：
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作者：
Long Chen;Bai-Qi Liu;M. Ni
摘要：通过三维（3D）和准二维（Q2D）数值模拟来研究电绝缘腔中的自然对流，该电绝缘腔具有与主环流垂直的水平磁场（MF），其中两个相对的垂直壁保持在不同的温度，其他四个是热绝缘的。我们主要关注 Hartmann (Ha⩽ 10 4) 和 Grashof (Gr⩽ 4× 10 7) 数处的流。研究发现，当 MF 较低时，由于洛伦兹力抑制沿 MF 线的二次流动，主对流加强，导致传热增强。一旦实现 Q2D，对流和传热将因 MF 的进一步增加而减弱。我们的数值结果证实了主对流的阻尼速度和动能以 Gr/Ha 为单位（参见参考文献 Takawa 等人（2002））。同时，计算出的平均努塞尔数 (Nu) 与 Okada 和 Ozoe (1992) 的实验结果非常吻合，可以作为 Ha/Gr 3/4 而不是 Ha/Gr 1/3 的函数进行相关。
Abstract Both three-dimensional (3D) and quasi-two-dimensional (Q2D) numerical simulations are conducted to study the natural convection in an electrically insulated cavity with imposed horizontal magnetic fields (MF) normal to the main circulation, where two opposite vertical walls are kept at different temperatures and the other four are thermally insulated. We mainly focus on flows at Hartmann (Ha⩽ 10 4) and Grashof (Gr⩽ 4× 10 7) numbers. It is found that, with lower MF, the strengthening of the main convection, which is due to the suppression of the secondary flow along the MF lines by the Lorentz forces, results in the enhancement of heat transfer. Once the Q2D is achieved, the convection and the heat transfer would be damped by the further increase of MF. Our numerical results have confirmed that the damping velocity and kinetic energy of main convection are scaled as Gr/Ha (see Ref. Tagawa et al.(2002)). At the same time, the computed average Nusselt number (Nu) agrees well with the experimental results of Okada and Ozoe (1992), which can be correlated as a function of Ha/Gr 3/4 rather than Ha/Gr 1/3.