Determination of kinetic boundary conditions for gas-vapor binary mixture and its application

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K06064
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Fluid engineering
• Research Institution: Hokkaido University
• Principal Investigator: Kobayashi Kazumichi 北海道大学, 工学研究院, 准教授 (80453140)
• Co-Investigator(Kenkyū-buntansha): 藤井 宏之 北海道大学, 工学研究院, 助教 (00632580) ; 渡部 正夫 北海道大学, 工学研究院, 教授 (30274484)
• Research Collaborator: KON Misaki
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 気体論境界条件 / 蒸発・凝縮 / 気泡崩壊現象 / キャビテーション / 分子動力学 / 分子気体力学 / 凝縮係数

Outline of Final Research Achievements

The aim of this study is to determine the kinetic boundary conditions for vapor (condensable gas) - gas (non-condensable gas) binary mixture. We also apply the boundary conditions for multi phase flow, especially for the analysis of bubble collapse problem.

In the present study period, molecular dynamics method was used to construct the kinetic boundary conditions for vapor-gas mixture at equilibrium. We also solved the problem of the bubble collapse using the boundary conditions obtained from the molecular dynamics simulation. As a result, it was suggested that a thin layer composed of non-condensable gas is formed in the vicinity of the gas-liquid interface when the bubble collapses, and it was indicated that the condensation coefficient becomes extremely low due to the influence of this layer. It was also revealed that the internal temperature field when bubble collapses was affected by a small amount of non-condensable gas contained in the bubble.

Free Research Field

分子流体力学

Academic Significance and Societal Importance of the Research Achievements

これまで蒸気分子の相変化現象に対して，その他の成分の分子の影響（例えば水分子の蒸発・凝縮現象に対する空気分子の影響）は明らかにされてこなかった．本研究より，非凝縮性気体分子が蒸気分子の蒸発・凝縮に大きな影響を及ぼすることが明らかとなった．これは学術的意義のみならず，医療やレーザーアブレーション技術などで見られるキャビテーション気泡崩壊現象の詳細な解析において有用な知見となる．