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Experimental simulation of volcanic steam blasts and jets at high pressure ratios

Austin, Joanna M. and Morgenstern, Mara S. and Kieffer, Susan W. (2008) Experimental simulation of volcanic steam blasts and jets at high pressure ratios. Eos, 89 (53). V34A04. ISSN 0096-3941. http://resolver.caltech.edu/CaltechAUTHORS:20141006-104143496

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Abstract

End-member compositions of plumes from volcanic eruptions range from nearly pure steam to heavily particle-laden gas flows. In all cases, if the plumes erupt from a high-pressure reservoir, they are initially supersonic jets that may have complex internal flow structures not easily documented in the field. In the laboratory, some properties of volcanic jets can be investigated with particle-laden flows, but other properties can only be investigated in optically transparent flows. We examine the relation of unsteady jet structure to reservoir conditions for optically transparent flows. We have developed an experimental shock tube facility capable of achieving pressure ratios up to ~150 with reservoirs of different shapes. Time-resolved schlieren visualization is combined with pitot pressure measurements to interrogate the structure of the underexpanded jet flow. We have done preliminary experiments at a pressure ration of 40 with air, with two reservoirs that are 12.6 and 20 cm in length. These initially produce well-defined supersonic jets that have properties (shape of the underexpanded jet; barrel shocks, Mach disk shocks) which we have bench-marked against other experiments and simulations. Estimated durations of the supersonic portions of the flow from pressure decay calculations are ~45 and ~75 ms, respectively. On these time-scales, the experimental jets collapse; the plume boundary and internal barrel shocks tighten and the Mach disk shock moves toward the vent, until subsonic conditions occur.


Item Type:Article
Additional Information:© 2008 American Geophysical Union.
Group:GALCIT
Record Number:CaltechAUTHORS:20141006-104143496
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20141006-104143496
Official Citation:Austin, Joanna M., Morgenstern, Mara S., and Kieffer, Susan W. (2008), Experimental simulation of volcanic steam blasts and jets at high pressure ratios, Eos Trans. AGU, 89(53), Fall meet. Suppl., Abstract V34A-04.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50206
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:06 Oct 2014 23:06
Last Modified:20 Sep 2016 23:02

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