Alexakis Alexandros, Ponty Yannick
Université de Nice Sophia-Antipolis, France (UNS).
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 May;77(5 Pt 2):056308. doi: 10.1103/PhysRevE.77.056308. Epub 2008 May 14.
An investigation of the dynamo instability close to the threshold produced by an ABC forced flow is presented. We focus on the on-off intermittency behavior of the dynamo and the countereffect of the Lorentz force in the nonlinear stage of the dynamo. The Lorentz force drastically alters the statistics of the turbulent fluctuations of the flow and reduces their amplitude. As a result, much longer bursts (on phases) are observed than is expected based on the amplitude of the fluctuations in the kinematic regime of the dynamo. For large Reynolds numbers, the duration time of the on phase follows a power law distribution, while for smaller Reynolds numbers the Lorentz force completely kills the noise and the system transits from a chaotic state into a laminar time periodic flow. The behavior of the on-off intermittency as the Reynolds number is increased is also examined. The connections with dynamo experiments and theoretical modeling are discussed.
本文对由ABC强迫流产生的接近阈值的发电机不稳定性进行了研究。我们关注发电机的开关间歇性行为以及发电机非线性阶段洛伦兹力的反作用。洛伦兹力极大地改变了流动湍流涨落的统计特性，并减小了其幅度。结果，观察到的爆发（开启阶段）比基于发电机运动学状态下涨落幅度所预期的要长得多。对于大雷诺数，开启阶段的持续时间遵循幂律分布，而对于较小的雷诺数，洛伦兹力完全消除了噪声，系统从混沌状态转变为层流时间周期流。我们还研究了随着雷诺数增加开关间歇性的行为。讨论了与发电机实验和理论建模的联系。
