Surrounding gas effects on instability at solid-gas-liquid three-phase contact line in high-speed liqdui film flow

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H03168
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Fluid engineering
• Research Institution: Hokkaido University
• Principal Investigator: Watanabe Masao 北海道大学, 工学研究院, 教授 (30274484)
• Co-Investigator(Kenkyū-buntansha): 真田 俊之 静岡大学, 工学部, 准教授 (50403978) ; 小林 一道 北海道大学, 工学研究院, 准教授 (80453140) ; 藤井 宏之 北海道大学, 工学研究院, 助教 (00632580)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 流体 / 混相流 / 液滴 / 液滴衝突 / スプラッシュ / 液捲流れ / 可視化

Outline of Final Research Achievements

Liquid droplet impacts on solid surface are key elements in technical applications, such as rapid spray cooling, ink-jet printing and semiconductor cleaning. Although the broad varieties of parameters that control splash formation after the droplet impact, are proposed, they are not thoroughly explored; hence, dynamics of the droplet after the impact are yet fully understood. After droplet impacts on solid surface, characteristic film flow is developed; then splash which consists of the secondary droplets ejected from the edge of the lamella may be generated. We investigated the surrounding-gas effects on the instability in the vicinity of the solid-gas-liquid triple-phase contact line of the ejected fast liquid film flow. We conducted four types of experiments: observation of thin-gas layer by color interferometry, droplet impact on solid surface with various wettability, high-speed droplet impact in the reduced pressure chamber, droplet impact in the condensable surrounding gas.

Free Research Field

流体力学

Academic Significance and Societal Importance of the Research Achievements

高速で進展する液膜が，周囲気体圧力が低下すると安定化することは15年程前から知られてはいるが，本研究を遂行することにより，周囲圧力のみではなく，固体表面の濡れ性や周囲気体の凝縮・蒸発現象も，進展液膜の不安定性に大きく影響を及ぼすことを明らかにした．これらの成果は，高速射出液膜の不安定現象に起因するsplashの発生メカニズム解明に大きく寄与する．さらに，高速液滴と固体面との衝突は，噴霧塗装，プラズマ溶射，スプレー乾燥，インクジェット印刷等の様々な産業分野におけるプロセスにおいて本質的に重要な物理過程であるため，これらの産業分野の新たな展開に寄与する．