Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published June 2010 | Published
Book Section - Chapter Open

Exhaust of Underexpanded Jets from Finite Reservoirs

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.

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.

Attached Files

Published - 385579.pdf

Files

385579.pdf
Files (1.8 MB)
Name Size Download all
md5:298ff69232068c22dfca4eb8cc0cc45d
1.8 MB Preview Download

Additional details

Created:
August 19, 2023
Modified:
October 17, 2023