Influence of gravity on collisions of monodispersed droplets in homogeneous isotropic turbulence

Ryo Onishi*, Keiko Takahashi, Satoru Komori

*この研究の対応する著者

研究成果: Article査読

34 被引用数 (Scopus)

抄録

This paper studies the gravity influence on collisions of monodispersed droplets in homogeneous isotropic turbulence by means of direct numerical simulations (DNSs). The DNS results show that, in certain Stokes and Reynolds regimes, collision frequencies are significantly reduced in the presence of gravity. Those decreases are mainly attributable to the decrease in the droplet relative velocity, since the change in radial distribution function-often referred to preferential concentration-is small. Further analysis of the results reveals that droplet sedimentation due to gravity shortens the droplet-fluid interaction time, consequently weakening the relative motions between droplets. These observations lead to an analytical model that can be used to estimate the velocity fluctuations of sedimenting particles under gravity. Utilizing this model, we constructed a further analytical model for estimating the gravitational influence on collisions. Given flow and particle parameters, the model calculates the ratio of collision frequencies with and without the effect of gravity. Past studies simply noted that the gravitational influence is negligible when the droplet sedimenting velocity is much smaller than the flow velocity fluctuations. Our analytical model further suggests that the gravitational influence on collisions of monodispersed cloud droplets with non-negligible sedimentation rates stays negligibly small even in high Reynolds number flows, such as those typically found in convective clouds.

本文言語English
論文番号045912PHF
ページ(範囲)1-8
ページ数8
ジャーナルPhysics of Fluids
21
12
DOI
出版ステータスPublished - 2009 12月
外部発表はい

ASJC Scopus subject areas

  • 計算力学
  • 凝縮系物理学
  • 材料力学
  • 機械工学
  • 流体および伝熱

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