论文标题
湍流热对流中的洛伦兹脉冲引起的间歇性波动
Intermittent fluctuations due to Lorentzian pulses in turbulent thermal convection
论文作者
论文摘要
通过数值模拟和随机建模研究了由于磁通驱动的热对流而引起的湍流运动。对流细胞的倾斜导致剪切流的形成和准周期性弛豫振荡的能量积分远非线性不稳定性的阈值。流体层中温度和径向速度波动的概率密度函数从湍流开始时的正态分布变为具有指数尾巴的分布，用于强驱动系统的大波动振幅。频率频谱密度具有指数形状，这是确定性混乱的标志。通过使用一种新型的反卷积方法，这表明是由于基础时间序列中的洛伦兹脉冲的存在而导致的，这表明指数频谱在湍流方案中也可以持续存在。
Turbulent motions due to flux-driven thermal convection is investigated by numerical simulations and stochastic modelling. Tilting of convection cells leads to the formation of sheared flows and quasi-periodic relaxation oscillations for the energy integrals far from the threshold for linear instability. The probability density function for the temperature and radial velocity fluctuations in the fluid layer changes from a normal distribution at the onset of turbulence to a distribution with an exponential tail for large fluctuation amplitudes for strongly driven systems. The frequency power spectral density has an exponential shape, which is a signature of deterministic chaos. By use of a novel deconvolution method, this is shown to result from the presence of Lorentzian pulses in the underlying time series, demonstrating that exponential frequency spectra can persist in also in turbulent flow regimes.
