Rayleigh–Bénard magnetoconvection with temperature modulation
Rayleigh–Bénard magnetoconvection with temperature modulation
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具有温度调制的瑞利-贝纳德磁对流
DOI：
10.1098/rspa.2020.0289
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
Saheli Mitra
中科院分区：
文献类型：
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作者：
S. Hazra;K. Kumar;Saheli Mitra
对瑞利-贝纳德几何中的调制磁对流进行了 Floquet 分析。正弦变化的温度施加在下板上。当瑞利数 Ra 增加到临界值 Rao 以上时，振荡磁对流开始。磁对流开始时的流动可能会随着外部调制而次谐波或谐波振荡。对于调制幅度 a 的可感知值，临界瑞利数 Rao 随调制频率 ω 非单调变化。温度调节可以推迟或提前磁对流的出现。磁对流总是在较大的 ω 值下谐波振荡。阈值 Rao 和相应的波数 ko 接近在没有调制的情况下（a = 0）的稳态磁对流的值，即 ω → ∞。两个不同的谐波不稳定区域合并形成一个不稳定区域，该不稳定区域具有两个局部最小值，以获得更高的钱德拉塞卡数 Q 值，这在本质上是新的。我们还观察到一种新型的双临界点，它涉及两组不同的简谐振动。还研究了 Q 和 Pr 的变化对阈值 Rao 和临界波数 ko 的影响。
Floquet analysis of modulated magnetoconvection in Rayleigh–Bénard geometry is performed. A sinusoidally varying temperature is imposed on the lower plate. As Rayleigh number Ra is increased above a critical value Rao, the oscillatory magnetoconvection begins. The flow at the onset of magnetoconvection may oscillate either subhar- monically or harmonically with the external modulation. The critical Rayleigh number Rao varies non-monotonically with the modulation frequency ω for appreciable value of the modulation amplitude a. The temperature modulation may either postpone or prepone the appearance of magnetoconvection. The magnetoconvective flow always oscillates harmonically at larger values of ω. The threshold Rao and the corresponding wavenumber ko approach to their values for the stationary magnetoconvection in the absence of modulation (a = 0), as ω → ∞. Two different zones of harmonic instability merge to form a single instability zone with two local minima for higher values of Chandrasekhar’s number Q, which is qualitatively new. We have also observed a new type of bicritical point, which involves two different sets of harmonic oscillations. The effects of variation of Q and Pr on the threshold Rao and critical wavenumber ko are also investigated.