Impact of reduced near-field entrainment of overpressured volcanic jets on plume development
Journal of Geophysical Research
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Abstract
Volcanic plumes are often studied using one-dimensional analytical models, which use an empirical entrainment ratio to close the equations. Although this ratio is typically treated as constant, its value near the vent is significantly reduced due to flow development and overpressured conditions. To improve the accuracy of these models, a series of experiments was performed using particle image velocimetry, a high-accuracy, full-field velocity measurement technique. Experiments considered a high-speed jet with Reynolds numbers up to 467,000 and exit pressures up to 2.93 times atmospheric. Exit gas densities were also varied from 0.18 to 1.4 times that of air. The measured velocity was integrated to determine entrainment directly. For jets with exit pressures near atmospheric, entrainment was approximately 30% less than the fully developed level at 20 diameters from the exit. At pressures nearly three times that of the atmosphere, entrainment was 60% less. These results were introduced into Plumeria, a one-dimensional plume model, to examine the impact of reduced entrainment. The maximum column height was only slightly modified, but the critical radius for collapse was significantly reduced, decreasing by nearly a factor of two at moderate eruptive pressures.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Impact of reduced near-field entrainment of overpressured volcanic jets on plume development |
| Series title | Journal of Geophysical Research |
| DOI | 10.1029/2011JB008862 |
| Volume | 117 |
| Issue | B05209 |
| Year Published | 2012 |
| Language | English |
| Publisher | American Geophysical Union |
| Publisher location | Washington, D.C. |
| Contributing office(s) | Cascades Volcano Observatory, Volcano Hazards Program |
| Description | 13 p. |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Journal of Geophysical Research |
| Country | United States |
| Google Analytic Metrics | Metrics page |