论文标题
在水平磁场的影响下，从瑞利 - 贝纳德对流中的稳定对流掷圈过渡到对流滚动
Transition from steady to oscillating convection rolls in Rayleigh-Bénard convection under the influence of a horizontal magnetic field
论文作者
论文摘要
在这项研究中，我们考虑了水平磁场对包含在长方体容器中的有限液体金属层（200 \ times 200 \ times 40 mm^3）中的雷利 - 贝纳德对流的影响。进行实验室实验，以测量以Prandtl编号为PR = 0.03的合金GAINSN中的温度和流场，并且在瑞利数范围内2.3 \ times 10^4 <ra <2.6 \ 2.6 \ times 10^5。场强的最大值为320 mt（HA = 2470，Q = 6.11 \ times 10^6）。磁场迫使流动形成二维滚动，平行于磁场线的方向。该实验证实了Busse和Clever的预测（J.MécaniqueThéoriqueet Appliquee，1983），他表明水平磁场的应用将稳定的二维滚动结构（Busse Balloon）延伸到更高的RA数字。当RA超过给定的Chandrasekhar数Q的临界值时，从稳定到时间依赖的振荡流的过渡也会发生，这也等同于降低比率q/ra。我们的测量结果表明，第一次发展的振荡显然具有二维性质，特别是观察到相邻对流掷骰大小的相互增加和减小，而没有沿磁场方向沿速度场中任何可检测的梯度形成任何可检测的梯度。以q/ra = 1的比率，出现了第一个3D结构，最初在磁场方向上略微倾斜卷的倾斜度。在此过程中，立即出现在相邻对流掷骰之间的空间中，由于埃克曼泵送驱动的次级流动，沿卷沿滚动进行了干扰。通过进一步降低Q/ra，向完全开发的三维结构，然后向湍流进行过渡。
In this study we consider the effect of a horizontal magnetic field on the Rayleigh-Bénard convection in a finite liquid metal layer contained in a cuboid vessel (200 \times 200 \times 40 mm^3). Laboratory experiments are performed for measuring temperature and flow field in the alloy GaInSn at Prandtl number Pr = 0.03 and in a Rayleigh number range 2.3 \times 10^4 < Ra < 2.6 \times 10^5. The field strength is varied up to a maximum value of 320 mT (Ha = 2470, Q = 6.11 \times 10^6). The magnetic field forces the flow to form two-dimensional rolls parallel to the direction of the field lines. The experiments confirm the predictions made by Busse and Clever (J. Mécanique Théorique et Appliquée, 1983) who showed that the application of the horizontal magnetic field extends the range in which steady two-dimensional roll structures exist (Busse balloon) towards higher Ra numbers. A transition from the steady to a time-dependent oscillatory flow occurs when Ra exceeds a critical value for a given Chandrasekhar number Q, which is also equivalent to a reduction of the ratio Q/Ra. Our measurements reveal that the first developing oscillations are clearly of two-dimensional nature, in particular a mutual increase and decrease in the size of adjacent convection rolls is observed without the formation of any detectable gradients in the velocity field along the magnetic field direction. At a ratio of Q/Ra = 1, the first 3D structures appear, which initially manifest themselves in a slight inclination of the rolls with respect to the magnetic field direction. Immediately in the course of this, there arise also disturbances in the spaces between adjacent convection rolls, which are advected along the rolls due to the secondary flow driven by Ekman pumping. The transition to fully-developed three-dimensional structures and then to a turbulent regime takes place with further lowering Q/Ra.
