著者

澤田 純平 吉野 正人 鈴木 康祐

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.84, no.861, pp.18-00023-18-00023, 2018 (Released:2018-05-25)

参考文献数

22

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Dynamic behavior of binary water droplets approaching each other in cloud is simulated by the improved two-phase lattice Boltzmann method with the Continuum Surface Force (CSF) model. This method does not need to solve the pressure Poisson equation and enables us to calculate two-phase flows with high density ratio accurately and efficiently. In this study, we investigate the effects of the Reynolds number Re, the Weber number We, the impact parameter B (the relative distance between the centers of two droplets), and the droplet size ratio on the behavior of the binary droplets for liquid-gas density ratio of 800. We first simulate a stationary liquid droplet in a gas to confirm the validity of the present method. We next simulate off-center approach of two equal-size droplets and investigate the effects of the Reynolds number and the Weber number. It is seen that at low Weber numbers of We ~ O(10-2), there are two types of behavior during approach of two equal-size droplets, namely coalescence and deviation. In this Weber number region, it is found that they can deviate from each other at low Reynolds numbers of Re ≲ O(1) in spite of B ≤ 1.0, whereas collision and subsequent coalescence occur at higher Reynolds numbers of Re ≳ O(10). We finally simulate approach of two unequalsize droplets with various size ratios. It is found that the behavior of the droplets is different from that in the case of the equal-size droplets owing to asymmetric velocity field and droplet deformation. In addition, the smaller droplet tends to deviate from its original path more significantly than the larger droplet.