论文标题
在中等雷诺数下的蒸发湍流喷气喷气喷气喷气喷气剂的直接数值模拟
Direct numerical simulation of an evaporating turbulent diluted jet-spray at moderate Reynolds number
论文作者
论文摘要
喷气式喷气式液滴的蒸发发生在几种工业应用和自然现象中。尽管该问题具有相关性，但由于湍流的范围很广以及涉及的大量液滴，对所涉及机制的令人满意的理解仍未达到。在这种情况下，我们以相对较高的雷诺数字（即RE = 10,000）处理了湍流喷射喷雾的DNS。我们专注于喷气机对蒸发过程的影响和液滴的优先隔离，将结果与在相应条件下的较低雷诺数（RE = 6,000）进行比较。该问题在使用点滴滴近似的混合Eulerian-Lagrangian框架中解决。介绍了对气体和分散阶段的详细统计分析。我们发现，随着批量RE从RE = 6,000增加到RE = 10,000，液滴汽化长度的增长会增长。我们将此结果归因于液滴的惯性与湍流气体相动态之间的复杂相互作用。特别是，在较高的RE下，较慢的液滴传质无法遵守倾向于固定过程的混合层的湍流波动。我们还发现了一个强烈的液滴聚类，该簇源是由混合层中的干空气夹带，并通过远场区域的小规模聚类机构加剧。我们将展示聚类如何创建强烈的异质液滴拉格朗日进化。所有这些方面都有助于总体液滴蒸发率的依赖性。最后，我们讨论了当前情况下通常用于喷雾建模的D平方定律的准确性。我们发现，根据环境条件使用该法律，液滴蒸发率被高估了。
The evaporation of dispersed, liquid droplets in jet-sprays occurs in several industrial applications and in natural phenomena. Despite the relevance of the problem, a satisfactory comprehension of the mechanisms involved has not still be achieved because of the wide range of turbulent scales and the huge number of droplets involved. In this context, we address a DNS of a turbulent jet spray at relatively high Reynolds number, i.e. Re=10,000. We focus on the effect of the jet Re on the evaporation process and the preferential segregation of droplets, comparing the outcomes also with a DNS at lower Reynolds number, Re = 6,000, in corresponding conditions. The problem is addressed in the hybrid Eulerian-Lagrangian framework employing the point-droplet approximation. Detailed statistical analysis on both the gas and dispersed phases are presented. We found that the droplet vaporization length grows as the bulk Re is increased from Re = 6,000 to Re = 10,000 keeping other conditions fixed. We attribute this result to the complex interaction between the inertia of the droplets and the turbulent gaseous phase dynamics. In particular, at higher Re, the slower droplet mass transfer is not able to comply with the faster turbulent fluctuations of the mixing layer that tend to fasten the process. We also found an intense droplet clustering which is originated by entrainment of dry air in the mixing layer and intensified by the small-scale clustering mechanism in the far-field region. We will show how clustering creates a strongly heterogeneous droplet Lagrangian evolution. All these aspects contribute to the Re dependence of the overall droplet evaporation rate. Finally, we discuss the accuracy of the d-square law, often used in spray modeling, for present cases. We found that using this law based on environmental conditions the droplet evaporation rate is overestimated.
