期刊
JOURNAL OF FLUID MECHANICS
卷 814, 期 -, 页码 592-613出版社
CAMBRIDGE UNIV PRESS
DOI: 10.1017/jfm.2017.13
关键词
atmospheric flows; homogeneous turbulence; particle/fluid flow
资金
- Directorate For Engineering
- Div Of Chem, Bioeng, Env, & Transp Sys [1454259] Funding Source: National Science Foundation
We report on optical field measurements of snow settling in atmospheric turbulence at Re-lambda = 940. It is found that the snowflakes exhibit hallmark features of inertial particles in turbulence. The snow motion is analysed in both Eulerian and Lagrangian frameworks by large-scale particle imaging, while sonic anemometry is used to characterize the flow field. Additionally, the snowflake size and morphology are assessed by digital in-line holography. The low volume fraction and mass loading imply a one-way interaction with the turbulent air. Acceleration probability density functions show wide exponential tails consistent with laboratory and numerical studies of homogeneous isotropic turbulence. Invoking the assumption that the particle acceleration has a stronger dependence on the Stokes number than on the specific features of the turbulence ( e.g. precise Reynolds number and large-scale anisotropy), we make inferences on the snowflakes' aerodynamic response time. In particular, we observe that their acceleration distribution is consistent with that of particles of Stokes number in the range St = 0.1-0.4 based on the Kolmogorov time scale. The still-air terminal velocities estimated for the resulting range of aerodynamic response times are significantly smaller than the measured snow particle fall speed. This is interpreted as a manifestation of settling enhancement by turbulence, which is observed here for the first time in a natural setting.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据