Interfacial instability in turbulent flow over a liquid film in a channel
Interfacial instability in turbulent flow over a liquid film in a channel
复制标题
DOI：
10.1016/j.ijmultiphaseflow.2011.02.010
复制
发表时间：
2011-09-01
影响因子：
3.8
通讯作者：
Zaki, T. A.
中科院分区：
文献类型：
--
作者：
Naraigh, L. O.;Spelt, P. D. M.;Zaki, T. A.
我们重新审视可变形界面的稳定性，该界面将充分发展的湍流气流与薄层层流液体分开。尽管这个问题之前已经受到相当多的关注，但目前还没有一种不需要拟合参数且使用经过实验验证的基态分布的模型。此外，湍流应力中波引起的扰动的重要性仍不清楚。为了解决这些突出的问题，我们研究了这个问题并引入了仅需要指定流量或压降的湍流基态速度；无需调整参数。该基态根据可用的实验数据以及直接数值模拟的结果进行了广泛的验证。此外，还研究了扰动对湍流应力分布的影响，并证明对于液层较薄的情况，扰动的影响很小。液体层的详细建模还引出了两种不稳定模式，“界面”和“内部”，其中前者是两者中更占主导地位的。我们表明，界面粗糙度有可能降低界面模式相对于内部模式的增长率，从而促进后者达到最危险模式的地位。此外，我们引入了一种近似方法来区分“慢”波和“快”波，后者是“临界层”引起的不稳定性的情况；我们证明，对于所研究的参数范围，绝大多数波都是“慢”的。最后，我们的线性稳定性预测与实验数据在波形开始、波速和波长的关键参数方面进行了比较；这些产量在实验误差范围内一致。 (c) 2011 Elsevier Ltd. 保留所有权利。
We revisit the stability of a deformable interface that separates a fully-developed turbulent gas flow from a thin layer of laminar liquid. Although this problem has received considerable attention previously, a model that requires no fitting parameters and that uses a base-state profile that has been validated against experiments is, as yet, unavailable. Furthermore, the significance of wave-induced perturbations in turbulent stresses remains unclear. To address these outstanding issues, we investigate this problem and introduce a turbulent base-state velocity that requires specification of a flow rate or a pressure drop only; no adjustable parameters are necessary. This base state is validated extensively against available experimental data as well as the results of direct numerical simulations. In addition, the effect of perturbations in the turbulent stress distributions is investigated, and demonstrated to be small for cases wherein the liquid layer is thin. The detailed modelling of the liquid layer also elicits two unstable modes, 'interfacial' and 'internal', with the former being the more dominant of the two. We show that it is possible for interfacial roughness to reduce the growth rate of the interfacial mode in relation to that of the internal one, promoting the latter, to the status of most dangerous mode. Additionally, we introduce an approximate measure to distinguish between 'slow' and 'fast' waves, the latter being the case for 'critical-layer'-induced instabilities; we demonstrate that for the parameter ranges studied, the large majority of the waves are 'slow'. Finally, comparisons of our linear stability predictions are made with experimental data in terms of critical parameters for onset of wave-formation, wave speeds and wavelengths; these yield agreement within the bounds of experimental error. (c) 2011 Elsevier Ltd. All rights reserved.