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International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Bubble Growth in Microgravity Under the Action of Electric Forces: Experiments and Numerical Simulation

Paolo Di Marco
Department of Energy, Systems, Constructions and Territory Engineering, University of Pisa, largo Lucio Lazzarino 1, 56122 PISA Italy

Ryo Kurimoto
University of Shiga Prefecture; Graduate School of Engineering, Kobe University, 1-1, Rokkodai, Nada, Kobe

Giacomo Saccone
DESTEC, University of Pisa Largo L. Lazzarino 1, Pisa, 56122, Italy

Kosuke Hayashi
Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe, 657-8501, Japan

Akio Tomiyama
Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe, 657-8501, Japan

DOI: 10.1615/IHTC15.tbf.008960
pages 7681-7691


KEY WORDS: Two-phase/Multiphase flow, Electrochemical transport, Bubble Dynamics, Microgravity, Electric Field, Numerical Methods

Abstract

The classical problem of growth and detachment of a bubble from an orifice is revisited in this study, to achieve a better comprehension of the role played by gravity and/or an additional electrostatic field on the bubble, with the aim to develop efficient and adequate numerical tools including the action of electric force. In particular, numerical simulation of the bubble growth was performed and compared with the experimental results obtained in a parabolic flight campaign (ESA-PF58). The experimental apparatus consisted in an orifice (0.40 mm in diameter) drilled in a flat stainless steel plate submerged in the test fluid (FC-72). Nitrogen was injected in the orifice by means of a flow controller. An electric potential up to 25 kV could be applied to a washer-shaped electrode located 6 mm above the plate and centered with the orifice axis. Data were acquired via a high speed video camera, equipped with a microscopic lens. Bubble images were digitized and processed via dedicated software, implemented in Matlab. Numerical simulations were carried out using an interface tracking method. The interface tracking is based on a level set method with a volume correction scheme. The ghost fluid method is used to evaluate surface tension force. The electric field is obtained by solving the equation of Gauss' law using a standard difference method. Two-dimensional cylindrical coordinate systems were used. Fairly good agreement was obtained for bubble shape in microgravity. Furthermore, the study of local bubble curvature allowed comparison with theoretical model of capillary and electric pressure at the interface.

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