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2. Maximum Solid Phase Concentration in Geophysical Turbulent Gas‐Particle Flows: Insights From Laboratory Experiments

Author

Weit, A, Roche, O, Dubois, T, and Manga, M

Subjects
Fluid Mechanics and Thermal Engineering, Engineering, gas-particle mixtures, turbulence, clustering, maximum particle concentration, particle Reynolds number, Meteorology & Atmospheric Sciences
Abstract

Abstract: The maximum solid phase concentration in geophysical turbulent gas‐particle mixtures is essential for understanding the flow dynamics but is poorly known. We present laboratory experiments on turbulent mixtures of air and ceramic particles generated in a vertical pipe. The mixtures had maximum bulk concentrations Cmax = 0.7–2.4 vol. % set by the onset of clustering and that increased with the degree of turbulence. Comparison with results of similar experiments with less dense (glass) particles reveals that Cmax increases with the particle Reynolds number according to Cmax = 0.78 × Rep0.17. Published results of experiments at specific Rep in different configurations are consistent with our data, suggesting that the model for Cmax may be generally applicable to turbulent mixtures. From our empirical laws we infer that natural turbulent gas‐particle flows with Rep ~ 102–105 have maximum solid concentrations of ~2–5 vol. %.

Published
2019

4. Experimental Measurement of the Solid Particle Concentration in Geophysical Turbulent Gas‐Particle Mixtures

Author

Weit, A, Roche, O, Dubois, T, and Manga, M

Subjects
gas-particle mixtures, particle concentration, cluster, pyroclastic density currents, volcanic plumes, snow avalanches, Geochemistry, Geology, Geophysics
Abstract

Dilute gas-particle mixtures in which the particles are carried by the turbulent fluid are found in various geophysical contexts, from cold snow avalanches to hot pyroclastic density currents. Though previous studies suggest that such mixtures have maximum particle concentrations of a few volume percent, the dependence of this maximum concentration on the Reynolds number is unclear. We addressed this issue through laboratory experiments in a vertical pipe, where dilute gas-particle mixtures were created by injecting a turbulent air flow from below. Nearly monodisperse mixtures of glass beads of different grain sizes (77 to 1,550 μm) were used with varying bulk concentrations from 0.025 to 8 vol. %. To create quasi-static mixtures, the mean air velocity matched the terminal settling velocity for the grain sizes investigated. The maximum Reynolds numbers of the mixtures were ~104–106. The air pressure indicated full support of the particle weight at concentrations down to 0.025 vol. %. Above a critical particle concentration, at which all the particles were suspended, subsequent additional particles were not maintained in the mixture and led to the formation of clusters that settled downward in the pipe to form a dense fluidized bed. Maximum mean particle concentrations of the dilute mixtures increased from ~1 to ~2.8 vol. % and reached a plateau at increasing mixture Reynolds number. These results give insights into the maximum particle concentrations of geophysical turbulent gas-particle mixtures and may serve to constrain observations as well as the input and output data of models.

Published
2018

6. MRI prostate contouring is not impaired by the use of a radiotherapy image acquisition set-up. An intra- and inter-observer paired comparative analysis with diagnostic set-up images

Author

Sabater, S., Pastor-Juan, M.R., Andres, I., López-Martinez, L., Lopez-Honrubia, V., Tercero-Azorin, M.I., Sevillano, M., Lozano-Setien, E., Jimenez-Jimenez, E., Berenguer, R., Rovirosa, A., Castro-Larefors, S., Magdalena Marti-Laosa, M., Roche, O., Martinez-Terol, F., and Arenas, M.

Published
2021
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31. MeMoVolc consensual document: a review of cross-disciplinary approaches to characterizing small explosive magmatic eruptions

Author

Gurioli, L., Andronico, D., Bachelery, P., Balcone-Boissard, H., Battaglia, J., Boudon, G., Burgisser, A., Burton, M. R., Cashman, K., Cichy, S., Cioni, R., Di Muro, A., Dominguez, L., D’Oriano, C., Druitt, T., Harris, A. J. L., Hort, M., Kelfoun, K., Komorowski, J. C., Kueppers, U., Le Pennec, J. L., Menand, T., Paris, R., Pioli, L., Pistolesi, M., Polacci, M., Pompilio, M., Ripepe, M., Roche, O., Rose-Koga, E., Rust, A., Schiavi, F., Scharff, L., Sulpizio, R., Taddeucci, J., and Thordarson, T.

Published
2015
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