Taylor drop in a closed vertical pipe

Picchi, Davide; Suckale, Jenny; Battiato, Ilenia

doi:10.1017/jfm.2020.596

Cited by 6 publications

(13 citation statements)

References 55 publications

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“…(2018) and Picchi et al. (2020), where is the density difference. Substituting into the continuity equations and matching the order, we get .…”

Section: Methodsmentioning

confidence: 98%

“…We model the response of core–annular flow to nucleation by formulating an evolution equation for the core thickness in a vertical conduit with depth-variable core density and viscosity using a lubrication approximation commonly used to study thin-film flow (Zhou et al. 2005; Cook, Bertozzi & Hosoi 2008; Wang & Bertozzi 2014; Mirzaeian & Alba 2018; Picchi, Suckale & Battiato 2020). We assume that the two magmas are immiscible.…”

Section: Introductionmentioning

confidence: 99%

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Disrupt the upper or the lower conduit? The dual role of gas exsolution in the conduits of persistently active volcanoes

2022

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Many volcanoes emit a significant portion of the gas they transport to the atmosphere during continual passive degassing rather than during eruptions. To maintain a high gas and thermal flux without erupting magma, the flow field in the volcanic conduit must be approximately balanced with gas-rich, buoyant magma ascending and degassed, heavy magma descending. In vertical conduits, this exchange flow takes the form of core–annular flow, where the gas-rich magma forms a core enclosed by an annulus of degassed magma. The flow dynamics of core–annular flow have been studied extensively in fluid dynamics, but mostly for constant material properties. Our study aims to advance our understanding of how core–annular flow responds to volatile exsolution – a simple, yet ubiquitous disruption in volcanic conduits, which alters both the density and the viscosity of the core fluid. By deriving an evolution equation for the core–annular interface based on a generalized exchange-flow condition using a lubrication approximation, we find that the response of the system to volatile exsolution depends on the conduit flow regime. The same nucleation event can lead to a flow adjustment only in the upper, only in the lower or in both portions of the volcanic conduit. Our results emphasize that the thermodynamic evolution of magma properties and volcanic conduit flow are intricately linked, which may help understand the observed variability of eruptive behaviour at persistently degassing volcanoes.

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“…(2018) and Picchi et al. (2020), where is the density difference. Substituting into the continuity equations and matching the order, we get .…”

Section: Methodsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Disrupt the upper or the lower conduit? The dual role of gas exsolution in the conduits of persistently active volcanoes

2022

Self Cite

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“…In all of our simulations, we assume that only the thick-core solution is realized since it is most commonly observed in experiments (Picchi et al, 2020;Stevenson & Blake, 1998).…”

Section: Boundary and Initial Conditionsmentioning

confidence: 99%

“…We verify and validate our numerical model, as well as the experimental methodology, by comparing our results to existing theoretical solutions and empirical correlations as described in detail in the supporting information. To evaluate our ability to capture the slug ascent speed in the initially stagnant liquid, we compare our experimental measurements, U s (Table 1), and the corresponding numerical reproduction to the analytical solution given by Picchi et al (2020) and the empirical speeds proposed by Viana et al (2003).…”

Section: Verification and Validationmentioning

confidence: 99%

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Interactions Between Gas Slug Ascent and Exchange Flow in the Conduit of Persistently Active Volcanoes

et al. 2021

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Many volcanoes around the world are persistently active with continuous degassing for years or even centuries, sometimes exceeding historic records. Such long‐term stability contrasts with short‐term instability, reflected in eruptive episodes that punctuate passive degassing. These two aspects of persistent activity, long‐term stability as opposed to short‐term instability, are often conceptualized through two distinct model frameworks: Exchange‐flow in volcanic conduits is commonly invoked to explain the long‐term thermal balance and sustained passive degassing, while the ascent of large gas slugs is called upon to understand explosive eruptions. While typically considered separately, we propose here that both flow processes could occur jointly in the conduits of persistently active volcanoes and in transient connections between subvolcanic melt lenses. To understand the dynamic interplay between exchange flow and slug ascent, we link analogue laboratory experiments with direct numerical simulations. We find that the two flows superimpose without creating major disruptions when only considering the ascent of a single gas slug. However, the sequential ascent of multiple gas slugs is disruptive to the ambient exchange flow, because it may entail continual buildup of buoyant magma at depth. While our study focuses on the laboratory scale, we propose that the dependence of exchange‐flow stability on sequential slug ascent is relevant for understanding why explosive sequences are sometimes followed by effusive eruptions. Taken together, our work suggests that integrating exchange flow and slug ascent could provide a more complete understanding of persistently active volcanoes than either model framework offers in isolation.

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Ascending non-Newtonian long drops in vertical tubes

et al. 2022

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We report on theoretical and experimental studies describing the buoyancy-driven ascent of a Taylor long drop in a circular vertical pipe where the descending fluid is Newtonian, and the ascending fluid is non-Newtonian yield shear thinning and described by the three-parameter Herschel–Bulkley model, including the Ostwald–de Waele model as a special case for zero yield. Results for the Ellis model are included to provide a more realistic description of purely shear-thinning behaviour. In all cases, lubrication theory allows us to obtain the velocity profiles and the corresponding integral variables in closed form, for lock-exchange flow with a zero net flow rate. The energy balance allows us to derive the asymptotic radius of the inner current, corresponding to a stable node of the differential equation describing the time evolution of the core radius. We carried out a series of experiments measuring the rheological properties of the fluids, the speed and the radius of the ascending long drop. For some tests, we measured the velocity profile with the ultrasound velocimetry technique. The measured radius of the ascending current compares fairly well with the asymptotic radius as derived through the energy balance, and the measured ascent speed shows a good agreement with the theoretical model. The measured velocity profiles also agree with their theoretical counterparts. We have also developed dynamic similarity conditions to establish whether laboratory physical models, limited by the availability of real fluids with defined rheological characteristics, can be representative of real phenomena on a large scale, such as exchanges in volcanic conduits. Appendix B contains scaling rules for the approximated dynamic similarity of the physical process analysed; these rules serve as a guide for the design of experiments reproducing real phenomena.

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Taylor drop in a closed vertical pipe

Abstract: Abstract

Cited by 6 publications

References 55 publications

Disrupt the upper or the lower conduit? The dual role of gas exsolution in the conduits of persistently active volcanoes

Disrupt the upper or the lower conduit? The dual role of gas exsolution in the conduits of persistently active volcanoes

Interactions Between Gas Slug Ascent and Exchange Flow in the Conduit of Persistently Active Volcanoes

Ascending non-Newtonian long drops in vertical tubes

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