Comparison of Two Gas Injection Methods for Generating Bubbles in a T-Junction
In this work, we compare the performance of two different methods for generating bubbles in conditions relevant to microgravity. A T-junction formed by two cylindrical (1 mm of internal diameter) and perpendicular channels is used to generate trains of non-wetting bubbles. Air and distilled water ar...
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| Formato: | artículo |
| Fecha de publicación: | 2020 |
| País: | España |
| Recursos: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/192420 |
| Acesso em linha: | https://hdl.handle.net/2117/192420 https://dx.doi.org/10.1007/s12217-020-09790-3 |
| Access Level: | acceso abierto |
| Palavra-chave: | Reduced gravity environments Microbubbles Microgravity Two-phase flow Bubble formation Microchannel T-junction Monodisperse bubbles Ambients de microgravetat Bombolles Àrees temàtiques de la UPC::Física |
| Resumo: | In this work, we compare the performance of two different methods for generating bubbles in conditions relevant to microgravity. A T-junction formed by two cylindrical (1 mm of internal diameter) and perpendicular channels is used to generate trains of non-wetting bubbles. Air and distilled water are used as dispersed and continuous phases, respectively. The difference between both methods lies in the strategy used to inject the fluids. In one case (here referred to as TJ-A configuration), the gas is injected into the side channel. In the other case (referred to as TJ-B), the gas is injected into the main channel. Bubble size dispersion is analyzed and quantified with the polydispersity index. The increase of the capillary number (based on the continuous phase) has shown a strong influence on the regularity of the bubble generation process. The TJ-A method can produce monodisperse bubbles at higher capillary numbers than configuration TJ-B. The limits of monodispersity, as far as the capillary number is concerned, are studied. These limits determine the optimal operating range of the T-junction for generating highly monodisperse bubbles. Beyond these limits, polydispersity increases, although much more abruptly in TJ-B than in TJ-A. The bubble generation frequency is also studied, with special attention to the two main regimes that characterize the frequency, i.e. the linear regime (at very low gas flow rate) and the saturation regime (at high gas flow rates). A new dimensionless expression of the bubble generation frequency is proposed in this work. |
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