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  • Cambridge University Press (CUP)  (3)
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  • Cambridge University Press (CUP)  (3)
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  • 1
    Online Resource
    Online Resource
    Role of microstructure and composition on natural convection during ternary alloy solidification
    Cambridge University Press (CUP) ; 2021
    In:  Journal of Fluid Mechanics Vol. 913 ( 2021-04-25)
    Details
    In: Journal of Fluid Mechanics, Cambridge University Press (CUP), Vol. 913 ( 2021-04-25)
    Abstract: Solidifying ternary systems can exhibit complex natural convection phenomena, particularly due to the presence of two porous zones (cotectic and primary mush), and the rejection of two differently dense solutes. The primary objectives of this study are to investigate the following: (i) the natural convection patterns in various compositional regimes of a typical ternary system, and (ii) the role of the combined existence of the microstructure (facets and dendrites) in the porous zone on natural convection, with a motivation to enhance the current understanding of the microstructure–convection relationships. A ternary mixture is chosen such that different compositions of the three primary solidifying components lead to the formation of distinct ice, dendritic and faceted solid structures that cover the complete span of microstructure–convection relationships. The observations of flow in different compositional regimes show convection occurring in the form of plumes, random mixing and double-diffusive layering, as well as combinations of these, which are governed by the type of coexisting microstructures. The study reveals the occurrence of Rayleigh–Taylor instability with varying amounts of the heavier component. The bulk liquid composition showed a tendency to cross the cotectic line, and thus also change the nature of primary solidifying structure from faceted to dendritic in cases where facets and dendrites were present in cotectic mush, and facets in primary mush. These insights are believed to elucidate the complex mechanisms of ternary solidification, as well as provide important real-time data for direct numerical simulations.
    Type of Medium: Online Resource
    ISSN: 0022-1120 , 1469-7645
    URL: Article
    DOI: 10.1017/jfm.2021.1
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2021
    detail.hit.zdb_id: 1472346-3
    detail.hit.zdb_id: 218334-1
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    Online Resource
  • 2
    Online Resource
    Online Resource
    On the mechanism responsible for unconventional thermal behaviour during freezing
    Cambridge University Press (CUP) ; 2020
    In:  Journal of Fluid Mechanics Vol. 903 ( 2020-11-25)
    Details
    In: Journal of Fluid Mechanics, Cambridge University Press (CUP), Vol. 903 ( 2020-11-25)
    Abstract: In this study, identical experiments of bottom-cooled solidification fluidic mixtures that exhibit faceted and dendritic microstructures were performed. The strength of compositional convection, created due to the rejection of a lighter solute, was correlated with the solidifying microstructure morphology via separate Rayleigh numbers in the mushy and bulk-fluid zones. While the bulk fluid in dendritic solidification experienced a monotonic decrease in the temperature, solidification of the faceted case revealed an unconventional, anomalous temperature rise in the bulk liquid after the formation of a eutectic solid. Based on the bulk-liquid temperatures, three distinct regimes of heat transfer were observed in the liquid, namely, convection-dominated, transition and conduction-dominated. The observations were analysed and verified with the help of different initial compositions and cooling conditions, as well as other mixtures that form faceted morphology upon freezing. The observed temperature rise was further ascertained by performing an energy balance in an indicative control volume ahead of the solid–liquid interface. The plausible mechanism of permeability-driven flow causing a gain in the temperature of the liquid during freezing was generalized with the help of a semi-analytical investigation of a one-dimensional system comprising solid, porous mush and liquid regions. The analytical scaling relations for fluid velocity and vorticity, for the faceted and dentritic cases, revealed contrasting vorticity values, which are much larger in low permeability (faceted case) and cause enhanced mixing in the bulk. The study sheds new insights into the role of microstructural morphology in governing the transport phenomena in the bulk liquid.
    Type of Medium: Online Resource
    ISSN: 0022-1120 , 1469-7645
    URL: Article
    DOI: 10.1017/jfm.2020.630
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2020
    detail.hit.zdb_id: 1472346-3
    detail.hit.zdb_id: 218334-1
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Microlayer dynamics during the growth process of a single vapour bubble under subcooled flow boiling conditions
    Cambridge University Press (CUP) ; 2022
    In:  Journal of Fluid Mechanics Vol. 931 ( 2022-01-25)
    Details
    In: Journal of Fluid Mechanics, Cambridge University Press (CUP), Vol. 931 ( 2022-01-25)
    Abstract: The phenomena of microlayer formation and its dynamic characteristics during the nucleate pool boiling regime have been widely investigated in the past. However, experimental works on real-time microlayer dynamics during nucleate flow boiling conditions are highly scarce. The present work is an attempt to address this lacuna and is concerned with developing a fundamental understanding of microlayer dynamics during the growth process of a single vapour bubble under nucleate flow boiling conditions. Boiling experiments have been conducted under subcooled conditions in a vertical rectangular channel with water as the working fluid. Thin-film interferometry combined with high-speed cinematography have been adopted to simultaneously capture the dynamic behaviour of the microlayer along with the bubble growth process. Transients associated with the microlayer have been recorded in the form of interferometric fringe patterns, which clearly reveal the evolution of the microlayer beneath the growing vapour bubble, the movement of the triple contact line and the growth of the dryspot region during the bubble growth process. While symmetric growth of the microlayer was confirmed in the early growth phase, the bulk flow-induced bubble deformation rendered asymmetry to its profile during the later stages of the bubble growth process. The recorded fringe patterns have been quantitatively analysed to obtain microlayer thickness profiles at different stages of the bubble growth process. For Re  = 3600, the maximum thickness of the almost wedge-shaped microlayer was obtained as δ  ~ 3.5 μm for a vapour bubble of diameter 1.6 mm. Similarly, for Re  = 6000, a maximum microlayer thickness of δ  ~ 2.5 μm was obtained for a bubble of diameter 1.1 mm.
    Type of Medium: Online Resource
    ISSN: 0022-1120 , 1469-7645
    URL: Article
    DOI: 10.1017/jfm.2021.958
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2022
    detail.hit.zdb_id: 1472346-3
    detail.hit.zdb_id: 218334-1
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
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