论文标题
湍流流的线性不稳定性
Linear instability of turbulent channel flow
论文作者
论文摘要
层状扰动图案形成是亚临界平面剪切流中间歇性制度的独特特征。通过对平面通道流进行广泛的数值模拟，我们表明该模式是由于线性不稳定性引起的湍流的空间调制。在许多实现中，我们在许多实现中对湍流脉冲的线性响应对湍流稳定的状态，就在不稳定性开始之前。分散关系是由整体平均松弛率构建的。随着不稳定性阈值的接近，最小阻尼模式的放松率最终达到零。尽管存在湍流波动，并且没有任何闭合模型，该方法允许准确估算发作时调制的波形。
Laminar-turbulent pattern formation is a distinctive feature of the intermittency regime in subcritical plane shear flows. By performing extensive numerical simulations of the plane channel flow, we show that the pattern emerges from a spatial modulation of the turbulent flow, due to a linear instability. We sample over many realizations the linear response of the fluctuating turbulent field to a temporal impulse, in the regime where the turbulent flow is stable, just before the onset of the instability. The dispersion relation is constructed from the ensemble-averaged relaxation rates. As the instability threshold is approached, the relaxation rate of the least damped modes eventually reaches zero. The method allows, despite the presence of turbulent fluctuations and without any closure model, for an accurate estimation of the wavevector of the modulation at onset.
