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Flow development and entrainment in turbulent particle-laden jets

June 3, 2023

Explosive eruptions expel volcanic gases and particles at high pressures and velocities. Within this multiphase fluid, small ash particles affect the flow dynamics, impacting mixing, entrainment, turbulence, and aggregation. To examine the role of turbulent particle behavior, we conducted an analogue experiment using a particle-laden jet. We used compressed air as the carrier fluid, considering turbulent conditions at Reynolds numbers from approximately 5,000 to 20,000. Two different particles were examined: 14-μm diameter solid nickel spheres and 13-μm diameter hollow glass spheres. These resulted in Stokes numbers between 1 and 35 based on the convective scale. The particle mass percentage in the mixture is varied from 0.3% to more than 20%. Based on a 1-D volcanic plume model, these Stokes numbers and mass loadings corresponded to millimeter-scale particle diameters at heights of 4–8 km above the vent during large, sustained eruptions. Through particle image velocimetry, we measured the mean flow behavior and the turbulence statistics in the near-exit region, primarily focusing on the dispersed phase. We show that the flow behavior is dominated by the particle inertia, with high Stokes numbers reducing the entrainment by more than 40%. When applied to volcanic plumes, these results suggest that high-density particles can greatly increase the probability of column collapse.

Publication Year 2023
Title Flow development and entrainment in turbulent particle-laden jets
DOI 10.1029/2022JD038108
Authors Laura K. Shannon, Bianca Viggiano, Raul Bayoan Cal, Larry G. Mastin, Alexa R. Van Eaton, Stephen A. Solovitz
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Geophysical Research: Atmospheres
Index ID 70245392
Record Source USGS Publications Warehouse
USGS Organization Volcano Science Center
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