论文标题
在湍流边界中惯性粒子转运的渐近闭合模型
Asymptotic closure model for inertial particle transport in turbulent boundary layers
论文作者
论文摘要
湍流边界层中重量化颗粒的转运方程可能来自基础空间概率密度函数（PDF）方程。但是，这些方程是未串联的，标准闭合方法是使用准正常近似（QNA），其中第四次矩近似近似为表现，就好像速度正态分布一样。除惯性弱的颗粒外，QNA还会导致较大的定量误差，并且与Sikovsky的已知渐近性预测（流湍流燃烧，第92卷，2014年，2014年，第41-64页），对于粘蛋白的sublayer，PDF时刻。我们基于渐近解决方案的粒子惯性效应很重要的区域中的转运方程来得出一个新的闭合近似。新的关闭与西科夫斯基的渐近预测一致，但即使在粘性的子层之外也适用。与直接数值模拟（DNS）的比较表明，当粘性Stokes编号为$ ST <10 $时，新的闭合与QNA相似的结果（与DNS相似），但对于$ ST> 10 $，新模型与DNS的一致性远胜于QNA。尽管新模型的预测留出了改进的空间，但结果表明，这种新的封闭策略是传统QNA方法的非常有效的替代方法，并且可以在未来的工作中进行完善。
Transport equations for heavy inertial particles in turbulent boundary layers may be derived from an underlying phase-space probability density function (PDF) equation. These equations, however, are unclosed, and the standard closure approach is to use a quasi-Normal approximation (QNA) in which the fourth moments are approximated as behaving as if the velocities were Normally distributed. Except for particles with weak inertia, the QNA leads to large quantitative errors, and is not consistent with the known asymptotic predictions of Sikovsky (Flow Turbulence Combust, vol. 92, 2014, pp. 41-64) for the moments of the PDF in the viscous sublayer. We derive a new closure approximation based on an asymptotic solution to the transport equations in regions where the effect of particle inertia is significant. The new closure is consistent with the asymptotic predictions of Sikovsky, but applies even outside the viscous sublayer. Comparisons with direct numerical simulations (DNS) show that the new closure gives similar results to the QNA (with the QNA results in slightly better agreement with the DNS) when the viscous Stokes number is $St<10$, but for $St>10$ the new model is in far better agreement with the DNS than the QNA. While the predictions from the new model leave room for improvement, the results suggest that this new closure strategy is a very effective alternative to the traditional QNA approach, and the closure could be refined in future work.
