Numerical simulations of the early stages of high-speed droplet breakup
Numerical simulations of the early stages of high-speed droplet breakup
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DOI：
10.1007/s00193-014-0546-z
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发表时间：
2015-07
期刊：
影响因子：
2.2
通讯作者：
J. C. Meng;T. Colonius
中科院分区：
文献类型：
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作者：
J. C. Meng;T. Colonius
文献中报道的实验是用数值模拟来研究正常激波后流动中水柱破裂的早期阶段。数值结果中观察到的破碎的定性特征，如圆柱体的初始流向扁平和圆柱体周围尖端的形成，支持了先前的剥离破碎的实验观测。此外，在圆柱体赤道处存在一个短暂的回流区，在尾迹中存在持续的上游喷流，并进行了讨论。在从实验和数值结果中提取测量值的不同方法所固有的不确定度内，与各种圆柱体变形测量的实验数据进行了比较，显示出很好的一致性。为了研究亚音速和超音速后激波流动转变的影响，我们将入射激波马赫数的范围扩展到实验所研究的范围之外。超音速激波后流动速度不会显著改变气缸的行为，也就是说，我们能够有效地折叠所有模拟激波马赫数的漂移、加速和阻力曲线。使用一种将噪声误差最小化的新方法，计算气缸的加速度；随后，通过按入射冲击波的压力比缩放，所有冲击马赫数的加速曲线都将折叠。此外，我们发现，在计算非定常阻力系数时，考虑了圆柱体的变形直径，使得阻力系数可以近似为初始解体期间的常数。
Experiments reported in the literature are reproduced using numerical simulations to investigate the early stages of the breakup of water cylinders in the flow behind normal shocks. Qualitative features of breakup observed in the numerical results, such as the initial streamwise flattening of the cylinder and the formation of tips at its periphery, support previous experimental observations of stripping breakup. Additionally, the presence of a transitory recirculation region at the cylinder’s equator and a persistent upstream jet in the wake is noted and discussed. Within the uncertainties inherent to the different methods used to extract measurements from experimental and numerical results, comparisons with experimental data of various cylinder deformation metrics show good agreement. To study the effects of the transition between subsonic and supersonic post-shock flow, we extend the range of incident shock Mach numbers beyond those investigated by the experiments. Supersonic post-shock flow velocities are not observed to significantly alter the cylinder’s behavior, i.e., we are able to effectively collapse the drift, acceleration, and drag curves for all simulated shock Mach numbers. Using a new method that minimizes noise errors, the cylinder’s acceleration is calculated; acceleration curves for all shock Mach numbers are subsequently collapsed by scaling with the pressure ratio across the incident shock. Furthermore, we find that accounting for the cylinder’s deformed diameter in the calculation of its unsteady drag coefficient allows the drag coefficient to be approximated as a constant over the initial breakup period.