Study on Surface-Tension-Convection Control Using Temperature and Electric Field

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K06190
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Thermal engineering
• 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): 2017-04-01 – 2020-03-31
• Keywords: 対流 / 表面張力流 / 不安定性 / 対流伝熱 / 熱ふく射 / 電場 / 液柱 / 液滴

Outline of Final Research Achievements

A study aiming at the control of surface-tension driven convection (STDC) through manipulation of temperature and electric fields has been conducted. The geometries are a liquid bridge (LB) formed in the gap between the opposing rods, a droplet suspended on the end face of the downward rod, and a horizontal liquid layer. The working fluid is silicone oil. The results are as follows. (1) Interfacial heat transfer affects the instability of STDC and the critical Marangoni number and dimensionless oscillation frequency are correlated with “heat-transfer ratio.” (2) In microgravity, the thermal radiation from LB is an important control factor for temperature/velocity distribution. (3) Application of an electric field to a droplet attenuates STDC if the temperature difference and applied voltage are small while it generates a complicated convection if both are large. Also, the dependence of surface tension on temperature/electrical potential was measured in a horizontal liquid layer.

Free Research Field

熱工学

Academic Significance and Societal Importance of the Research Achievements

表面張力流は、温度差、電位差、濃度差によって駆動され、マイクロ流れ、溶液流れ、微小重力環境下の液流の主因である。特に、気泡、液膜、液滴、液柱など、表面力が体積力を凌駕する系では表面張力流の役割が支配的となる。本研究では、温度場と電場を操作することによって表面張力流を制御するための基礎研究を行った。即ち、界面熱移動が表面張力流の不安定に与える影響、微小重力環境に置かれた液柱の気液界面からのふく射伝熱の影響、下向きロッド端面に懸架された液滴の温度差表面張力流への電場の影響、水平液体層に印可した温度差・電位差への表面張力の依存性を明らかにした。