A numerical study of the flow fields around falling hails
A numerical study of the flow fields around falling hails
复制标题
冰雹周围流场的数值研究
DOI：
10.1016/j.atmosres.2013.05.016
复制
发表时间：
2013
影响因子：
5.5
通讯作者：
Pao K. Wang
中科院分区：
文献类型：
--
作者：
K. Cheng;Pao K. Wang
研究了直径为1 ~ 10 cm的降雹周围流场的特性。通过数值求解随时间变化的Navier-Stokes方程，得到了假设为光滑球体的冰雹流场。冰雹的下落速度是根据观测得来的值计算的。这些流场的雷诺数在5780 ~ 206000之间。从流迹图、压力偏差、z-速度场和涡度场等方面讨论了这些场的特征。当上游流动保持准稳定时，这些场的尾迹变得越来越湍流，并且随着雷诺数的增加，再循环气泡侧翼的最大速度区呈现出环状脱落现象。计算了每种情况下的涡长和阻力系数，并给出了经验关系式。本文还讨论了这些特征对冰雹云物理的潜在影响。最后对今后的工作进行了展望。
The characteristics of the flow fields around falling hailstones of diameters 1 to 10 cm are studied. The flow fields are obtained by numerically solving the time-dependent Navier–Stokes equations for flow past hails which are assumed to be smooth spheres. The fall velocities of the hails are based on observational derived values. The Reynolds numbers of these flow fields range from 5780 to 206,000. The characteristics of these fields are discussed according to the streamtrace pattern, pressure deviation,z-velocity and vorticity fields. While the upstream flow remains quasi-steady, the wakes of these fields are increasingly turbulent and the maximum velocity region flanking the recirculation bubble exhibits a ring-shedding phenomenon as the Reynolds number increases. The eddy length and drag coefficient for each cases are also calculated and empirical relations are provided. Potential impacts of these characteristics to the cloud physical of hail are also discussed. An outlook of future works is also given.