Active control of convection and mixing in thin liquid layer through surface-tension manipulation

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04322
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 19020:Thermal engineering-related
• Research Institution: Yokohama National University
• Principal Investigator: Nishino Koichi 横浜国立大学, 大学院工学研究院, 教授 (90192690)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 対流 / 表面張力流 / 液膜 / 数値解析 / 次元解析 / レーザ加熱 / 能動制御

Outline of Final Research Achievements

Control of thermocapillary convection in thin liquid film is studied by means of the manipulation of surface tension at gas-liquid interface through the spot heating with a CO2 laser. The results are as follows. (1) A spot heating system is constructed by using a two-dimensional traversing mechanism. Stationary heating and linear-motion-type dynamic heating are given to the liquid film and experimental results for various laser powers, liquid film thickness, kinematic viscosities and traversing speeds are systematically accumulated. (2) A numerical technique for thermocapillary convection due to spot heating is proposed and its validity and accuracy is confirmed through the comparison with the experimental results. (3) The profiles of surface velocity due to spot heating show the presence of the 1st and 2nd peaks, and such unique characteristics are explained using non-dimensional parameters derived from the dimensional analysis.

Free Research Field

熱工学

Academic Significance and Societal Importance of the Research Achievements

表面張力流は、液膜、液滴、気泡、液柱など、代表寸法が小さい気液界面の対流を支配する。本研究では、温度差駆動の表面張力流をCO2レーザの静的／動的スポット加熱によって操作することによって、小スケール界面における対流を能動制御する方法論を研究した。レーザ出力、液膜厚さ、動粘性係数、走査速度を変化させて取得した実験データの蓄積とともに、数値解析の方法も考案し、検証した。得られた研究成果から、薄液膜に局所対流を自在に生起・制御することが可能となり、薄液膜を対象とした新しい応用技術であるマイクロ流体制御、マイクロ物体搬送、局所混合制御、結晶成長制御など、幅広い工学分野での利用が期待できる。