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Exhaust of Underexpanded Jets from Finite Reservoirs

Orescanin, M. M. and Prisco, D. and Austin, J. M. (2010) Exhaust of Underexpanded Jets from Finite Reservoirs. In: 40th Fluid Dynamics Conference and Exhibit. AIAA , Reston, VA. ISBN 978-1-61738-922-1. http://resolver.caltech.edu/CaltechAUTHORS:20140929-134308323

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Abstract

We examine the response of an underexpanded jet to a depleting, finite reservoir with experiments and simulations. An open-ended shock tube facility with variable reservoir length is used to obtain images of nitrogen and helium jet structures at successive instances during the blowdown from initial pressure ratios of up to 250. The reservoir and ambient pressures are simultaneously measured to obtain the instantaneous pressure ratio. We estimate the time-scales for jet formation and reservoir depletion as a function of the specific heat ratio of the gas and the initial pressure ratio. The jet structure formation time-scale is found to become approximately independent of pressure ratio for ratios greater than 50. In the present work, no evidence of time-dependence in the Mach disk shock location is observed for rates of pressure decrease associated with isentropic blowdown of a finite reservoir while the pressure ratio is greater than 15. The shock location in the finite- reservoir jet can be calculated from an existing empirical fit to infinite-reservoir jet data evaluated at the instantaneous reservoir pressure. For pressure ratios below 15, however, the present data deviate from a compilation of data for infinite-reservoir jets. A new fit is obtained to data in the lower pressure regime. The self-similarity of the jet structure is quantified and departure from similarity is noted to begin at pressure ratios lower than about 15, approximately the same ratio which limits existing empirical fits.


Item Type:Book Section
Related URLs:
URLURL TypeDescription
http://arc.aiaa.org/doi/abs/10.2514/6.2010-5108PublisherArticle
http://dx.doi.org/10.2514/6.2010-5108DOIArticle
Additional Information:© 2010 by University of Illinois. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. AIAA 2010-5108. The authors gratefully acknowledge interactions with Prof. Susan Kieffer in this study. This work was supported in part by NSF grant EAR06-09712, NSF grant SK2008-0035 8 ANTC and Charles R. Walgreen endowed funds to Susan W. Kieffer. We are grateful to Dr. James Quirk for the use of his code Amrita. We thank David Buchta for performing modeling runs with a different code to cross-check our results.
Group:GALCIT
Funders:
Funding AgencyGrant Number
NSFEAR06-09712
NSFSK2008-0035 8 ANTC
Charles R. Walgreen endowed fundsUNSPECIFIED
Record Number:CaltechAUTHORS:20140929-134308323
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140929-134308323
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50102
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:29 Sep 2014 21:11
Last Modified:20 Sep 2016 23:02

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