论文标题
强度条纹磁场对湍流热对流的影响
Effects of strong fringing magnetic fields on turbulent thermal convection
论文作者
论文摘要
我们研究条纹磁场对水平扩展矩形域中湍流热对流的影响。磁场是在两个半无限平面磁极之间的间隙中产生的，对流层位于间隙边缘附近。我们在此设置中采用直接的数值模拟，用于固定的雷利和较小的prandtl数字，但是通过控制磁极和对流电池之间的间隙来改变边缘宽度。磁体产生的磁场足以停止对流电池的高磁通量区域的流动。我们观察到，随着局部垂直磁场强度的提高，大规模结构变得更薄，并垂直于纵向侧壁。我们确定局部努塞尔特和雷诺数作为局部Hartmann数字的函数（基于磁场的垂直成分），并估计全球热量和动量传输。我们表明，对于强磁场，全局热传输随着边缘宽度的增加而降低，但随着弱磁场的边缘宽度的增加而增加。在大型垂直磁场的区域中，对流运动局限于侧壁附近。这些壁模式的幅度显示出对边缘宽度的非单调依赖性。
We study the influence of fringing magnetic fields on turbulent thermal convection in a horizontally extended rectangular domain. The magnetic field is created in the gap between two semi-infinite planar magnetic poles, with the convection layer located near the edge of the gap. We employ direct numerical simulations in this setup for fixed Rayleigh and small Prandtl numbers, but vary the fringe-width by controlling the gap between the magnetic poles and the convection cell. The magnetic field generated by the magnets is strong enough to cease the flow in high magnetic flux region of the convection cell. We observe that as the local vertical magnetic field strength increases, the large scale structures become thinner and align themselves perpendicular to the longitudinal sidewalls. We determine the local Nusselt and Reynolds numbers as functions of the local Hartmann number (based on the vertical component of the magnetic field) and estimate the global heat and momentum transport. We show that the global heat transport decreases with increasing fringe-width for strong magnetic fields but increases with increasing fringe-width for weak magnetic fields. In the regions of large vertical magnetic fields, the convective motion becomes confined to the vicinity of the sidewalls. The amplitudes of these wall modes show a non-monotonic dependence on the fringe-width.
