Turbulent entrainment in buoyant jet rising in a stratified crossflow: New constraints from laboratory experiments
Abstract
Predictions for the heights and downwind trajectories of volcanic plumes using integral models are critical for the assessment of risks and climate impacts of explosive eruptions, but are strongly influenced by parameterizations of turbulent entrainment. We compare four popular parameterizations using small scale laboratory experiments spanning the large range of dynamical regimes in which volcanic eruptions occur. We reduce uncertainties on the wind entrainment coefficient β, the leading source of uncertainty in plume models, which quantifies the contribution of wind-driven radial velocity shear to turbulent entrainment. We show that models better predict plume trajectories if: i) β is constant or increases with the plume buoyancy to momentum flux ratio ii) the superposition of the axial and radial velocity shear contributions to the turbulent entrainment is quadratic rather than a linear. Our results have important implications for, e.g., the prediction of the collapse of volcanic columns and production of pyroclastic flows.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.V23E0524C
- Keywords:
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- 1099 General or miscellaneous;
- GEOCHEMISTRY;
- 3699 General or miscellaneous;
- MINERALOGY AND PETROLOGY;
- 8499 General or miscellaneous;
- VOLCANOLOGY