Altmeyer Sebastian
Castelldefels School of Telecom and Aerospace Engineering, Universitat Politècnica de Catalunya, 08034, Barcelona, Spain.
Sci Rep. 2021 Feb 25;11(1):4705. doi: 10.1038/s41598-021-84175-z.
There is a huge number of natural and industrial flows, which are subjected to time-dependent boundary conditions. The flow of a magnetic fluid under the influence of temporal modulations is such an example. Here, we perform numerical simulations of ferrofluidic Couette flow subject to time-periodic modulation (with frequency [Formula: see text]) in a spatially homogeneous magnetic field and report how such a modulation can lead to a significant Reynolds number Re enhancement. Consider a modified Niklas approximation we explain the relation between modulation amplitude, driving frequency and stabilization effect. From this, we describe the system response around the primary instability to be sensitive/critical by an alternating field. We detected that such an alternating field provides an easy and in particular accurate controllable key parameter to trigger the system to change from subcritical to supercritical and vice versa. Our findings provide a framework to study other types of magnetic flows driven by time-dependent forcing.
存在大量自然和工业流动，它们受到随时间变化的边界条件的影响。磁流体在时间调制影响下的流动就是这样一个例子。在此，我们对在空间均匀磁场中受时间周期调制（频率为[公式：见原文]）的铁磁流体库埃特流进行了数值模拟，并报告了这种调制如何导致显著的雷诺数Re增强。考虑一种改进的尼克拉斯近似，我们解释了调制幅度、驱动频率和稳定效应之间的关系。据此，我们描述了围绕主要不稳定性的系统响应对于交变场是敏感/关键的。我们发现这样的交变场提供了一个易于且特别精确可控的关键参数，以触发系统从亚临界转变为超临界，反之亦然。我们的研究结果提供了一个框架，用于研究由时间相关强迫驱动的其他类型的磁流。
