Numerical Study of Motion of Falling Conical Graupel
Numerical Study of Motion of Falling Conical Graupel
复制标题
圆锥形霰弹下落运动的数值研究
DOI：
10.1016/j.atmosres.2017.09.008
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发表时间：
2017
影响因子：
5.5
通讯作者：
Hashino, T
中科院分区：
文献类型：
--
作者：
Chueh, C;Wang, P;Hashino, T
本文通过求解瞬态Navier-Stokes方程和六自由度运动的物体动力学方程，数值研究了具有实际密度范围的圆锥形霰自由下落的姿态。这个框架使我们能够确定的位置和方向的？结果表明，更显着的水平运动的情况下，与固定的体积密度的冰在我们以前的研究假设。这是因为真实的的霰粒子的密度小于冰的体积密度，这反过来又导致了相对较小的质量和相对较小的惯性矩。结果表明，当雷诺数较小时，在六个自由度下会发生典型的阻尼振荡，而当雷诺数较高时，会发生放大振荡，从而导致更复杂和不可预测的飞行姿态，如翻滚。在本研究中获得的阻力系数与以前的研究一致，可以近似为相同雷诺数的球体。我们还表明，圆锥形的霰可以进行显着的水平平移，可以在1小时内的1公里的数量级。
In the present study, the attitudes of freely-falling conical graupel with a realistic range of densities are investigated numerically by solving the transient Navier-Stokes equations and the body dynamics equations representing the 6-degrees-of-freedom motion. This framework allows us to determine the position and orientation of the graupel in response to the hydrodynamic force of the flow fields. The results show more significant horizontal movements than those cases with a fixed bulk density of ice assumed in our previous study. This is because the real graupel particles possess the density less than the bulk density of ice, which, in turn, leads to a relatively small mass and a relatively small set of moments of inertia. We demonstrate that, with the six degrees of freedom considered together, when Reynolds number is small, a typical damped oscillation occurs, whereas when Reynolds number is high, amplifying oscillation may occur which leads to more complicated and unpredictable flying attitudes such as tumbling. The drag coefficients obtained in the present study agree with the previous studies and can be approximated by that of spheres of the same Reynolds numbers. We also show that conical graupel can perform significant horizontal translations which can be on the order of 1 km in 1 h.