Dense spray evaporation as a mixing process
Dense spray evaporation as a mixing process
复制标题
DOI：
10.1103/physrevfluids.1.014201
复制
发表时间：
2016-05-18
影响因子：
2.7
通讯作者：
Villermaux, E.
中科院分区：
文献类型：
--
作者：
de Rivas, A.;Villermaux, E.
我们探索了一组密集的小液滴（喷雾）在干燥、搅拌的气相中蒸发的过程。微米大小的液体（水或乙醇）滴的密集喷雾是在空气中形成的气动雾化器在一个封闭的腔室。所述喷雾在周围空气中作为羽流输送，其延伸取决于稀释介质的相对湿度。标准剪切不稳定性在羽流边缘发展，形成与被动标量相似的拉伸层状结构。然而，与被动标量不同，这些薄片在有限的时间内消失，因为单个液滴在与干燥环境接触时在其边界蒸发。实验表明，嵌入在薄片中的单个液滴的寿命比通常描述单个液滴在静止环境中蒸发命运的d(2)定律所期望的要大得多。通过类比从被动标量的对流扩散方程理解混合时间的方式，我们证明了以恒定速率拉伸的喷雾片层的寿命。t(v) = 1/ ln（1+ /）这里是一个包含了稀释相中蒸汽的热力学和扩散特性的参数。本文还研究了随时间变化的拉伸率。密集的喷雾几乎表现为一个（非保守的）被动标量。
We explore the processes bywhich a dense set of small liquid droplets (a spray) evaporates in a dry, stirred gas phase. Adense spray of micron-sized liquid (water or ethanol) droplets is formed in air by a pneumatic atomizer in a closed chamber. The spray is conveyed in ambient air as a plume whose extension depends on the relative humidity of the diluting medium. Standard shear instabilities develop at the plume edge, forming the stretched lamellar structures familiar with passive scalars. Unlike passive scalars however, these lamellae vanish in a finite time, because individual droplets evaporate at their border in contact with the dry environment. Experiments demonstrate that the lifetime of an individual droplet embedded in a lamellae is much larger than expected from the usual d(2) law describing the fate of a single drop evaporating in a quiescent environment. By analogy with the way mixing times are understood from the convection-diffusion equation for passive scalars, we show that the lifetime of a spray lamellae stretched at a constant rate. is t(v) = 1/gamma ln(1+phi/phi), where phi is a parameter that incorporates the thermodynamic and diffusional properties of the vapor in the diluting phase. The case of time-dependent stretching rates is examined too. A dense spray behaves almost as a (nonconserved) passive scalar.