A Numerical Study on the Aerodynamics of Freely Falling Planar Ice Crystals
A Numerical Study on the Aerodynamics of Freely Falling Planar Ice Crystals
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DOI：
10.1175/jas-d-18-0041.1
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发表时间：
2018-08
影响因子：
3.1
通讯作者：
Joseph J. Nettesheim;Pao K. Wang
中科院分区：
文献类型：
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作者：
Joseph J. Nettesheim;Pao K. Wang
通过数值求解非定常、不可压缩的Navier-Stokes方程，利用商用计算流体动力学软件包研究了平面冰晶下落时的流场和下落形态。冰晶的运动和取向是明确模拟的基础上，水动力和扭矩代表6个自由度。这项研究扩展了目前的框架，通过调查四个平面型冰晶：晶体与扇形分支，晶体与广泛的分支，恒星晶体，和普通的树枝状晶体。晶体的最大尺寸范围为0.2至5 mm，对应于雷诺数范围为0.2至384。结果表明：雷诺数小于100的流动产生稳定流场;较大的板产生非定常流场，并表现出水平平移、旋转和振荡。给出了阻力系数、900百帕终端速度和通风效应的经验公式。降落轨迹，压力分布，尾流结构，蒸汽场和涡量场进行了检查。
Fluid flow fields and fall patterns of falling planar ice crystals are studied by numerically solving the unsteady, incompressible Navier–Stokes equations using a commercially available computational fluid dynamics package. The ice crystal movement and orientation are explicitly simulated based on hydrodynamic forces and torques representing the 6 degrees of freedom. This study extends the current framework by investigating four planar-type ice crystals: crystals with sector-like branches, crystals with broad branches, stellar crystals, and ordinary dendritic crystals. The crystals range from 0.2 to 5 mm in maximum dimension, corresponding to Reynolds number ranges from 0.2 to 384. The results indicate that steady flow fields are generated for flows with Reynolds numbers less than 100; larger plates generate unsteady flow fields and exhibit horizontal translation, rotation, and oscillation. Empirical formulas for the drag coefficient, 900-hPa terminal velocity, and ventilation effect are given. Fall trajectory, pressure distribution, wake structure, vapor field, and vorticity field are examined.