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Author: search.filters.author.Jones JRHas files: Yes

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    Transport and sedimentation of Pyroclastic Density Currents across topographic obstacles
    (Elsevier B.V., 2025-12) Corna L; Lube G; Uhle DH; Brosch E; Jones JR; Manga M; Andrews B
    Pyroclastic density currents (PDCs) can cross significant topographic obstacles. The processes that govern the interaction of PDCs with obstacles remain poorly understood leaving uncertainty in hazard planning and mitigation. Here, we report the results of large-scale experimental PDCs comprising hot volcanic particles and gas propagating across ridge-shaped obstacles. Observations from high-speed video and measurements of the velocity, density and temperature structure of the flows are used to identify the flow processes that occur when PDCs propagate across and become partially blocked by hill-shaped topographic obstacles; and how these characteristics are recorded in PDC deposits. The experiments show that the interaction of PDCs with ridges generate strong local perturbations to the internal flow velocity, density and temperature structure. These flow changes are linked to three main processes: the blocking of the lower, concentrated flow region in front of the obstacle; the compression and acceleration of the non-blocked flow regions on the stoss side; and the flow detachment behind the crest and formation of a turbulent wake before flow re-attachment downstream. Flow-topography interactions result in deposition and erosion rates that vary by three and two orders of magnitude, respectively, which explain the strong asymmetry of PDC deposits across topographic obstacles. The facies architecture of experimental deposits across ridges resembles those of natural PDC deposits from Te Maari and Taupō volcanoes (New Zealand). The findings of this study can guide the interpretation of PDC deposits or be taken into consideration in numerical models simulating the propagation of PDCs across complex topography for hazard forecast.
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    Turbulent particle-gas feedback exacerbates the hazard impacts of pyroclastic density currents
    (Springer Nature Limited, 2024-05-09) Uhle DH; Lube G; Breard ECP; Meiburg E; Dufek J; Ardo J; Jones JR; Brosch E; Corna LRP; Jenkins SF; Doronzo D; Aslin J
    Causing one-third of all volcanic fatalities, pyroclastic density currents create destruction far beyond our current scientific explanation. Opportunities to interrogate the mechanisms behind this hazard have long been desired, but pyroclastic density currents persistently defy internal observation. Here we show, through direct measurements of destruction-causing dynamic pressure in large-scale experiments, that pressure maxima exceed theoretical values used in hazard assessments by more than one order of magnitude. These distinct pressure excursions occur through the clustering of high-momentum particles at the peripheries of coherent turbulence structures. Particle loading modifies these eddies and generates repeated high-pressure loading impacts at the frequency of the turbulence structures. Collisions of particle clusters against stationary objects generate even higher dynamic pressures that account for up to 75% of the local flow energy. To prevent severe underestimation of damage intensities, these multiphase feedback processes must be considered in hazard models that aim to mitigate volcanic risk globally.
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    Modelling the role of oral processing on in vivo aroma release of white rice: Conceptual model and experimental validation
    (Elsevier Ltd, 2021-04) How MS; Jones JR; Morgenstern MP; Gray-Stuart E; Bronlund JE; Saint-Eve A; Trelea IC; Souchon I
    A conceptual model was developed to relate oral processing parameters and aroma release of cooked white rice. The conceptual model indicates that aroma release is dependent on the increase of particle surface area, the dilution effect of saliva and the diffusion of aroma from food residues that can be trapped in the buccal-pouches in the mouth. The model was validated against in vivo retro-nasal aroma release data during the consumption of rice flavoured with two aroma compounds (2-nonanone and ethyl propanoate) by five panellists. The oral processing behaviour of each subject was characterised at four different stages during oral processing by measuring bolus particle size, saliva content and the amount of residue particles that could be washed from the mouth after bolus expectoration. The results showed that aroma release for all subjects were dependent on the particle breakdown pathways used in oral processing. Subjects who reduced the rice to smaller particle sizes, higher pasted fraction and higher bolus residues had higher aroma release as expected from the conceptual model. Accounting for the physiological variables of subjects, the physicochemical parameters of aroma compounds and using a larger number of subjects in future studies will improve the model reliability.
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    Research Report - Repurposing Grape Marc
    (Marlborough District Council, 2020-03-06) Jones JR; McLaren S; Chen Q; Seraj M
    Section 1. Executive Report (page 2) Section 2. Background to the Project (page 25) Section 3. Detail Report - Thermal Processes: Technical and Economic Analysis (page 35) Section 4. Detail Report - Environmental Analysis by Carbon Footprint (page 69)