Wall pressure unsteadiness and side loads in overexpanded rocket nozzles

Baars, W, Tinney, C, Ruf, J, Brown, A and McDaniels, D 2012, 'Wall pressure unsteadiness and side loads in overexpanded rocket nozzles', AIAA Journal, vol. 50, no. 1, pp. 61-73.

Document type: Journal Article
Collection: Journal Articles

Title Wall pressure unsteadiness and side loads in overexpanded rocket nozzles
Author(s) Baars, W
Tinney, C
Ruf, J
Brown, A
McDaniels, D
Year 2012
Journal name AIAA Journal
Volume number 50
Issue number 1
Start page 61
End page 73
Total pages 13
Publisher American Institute of Aeronautics and Astronautics, Inc.
Abstract Surveys of both the static and dynamic wall pressure signatures on the interior surface of a subscale, cold-flow, and thrust-optimized parabolic nozzle are conducted during fixed nozzle pressure ratios corresponding to free shock separation and restricted shock separation states. The motive is to develop a better understanding for the sources of off-axis loads during the transient startup of overexpanded rocket nozzles. During free shock separation state, pressure spectra reveal frequency content resembling shock wave turbulent boundary-layer interaction. Presumably, when the internal flow is in restricted shock separation state, separation bubbles are trapped by shocks and expansion waves; interactions between the separated flow regions and the waves produce asymmetric pressure distributions. An analysis of the azimuthal modes reveals how the breathing mode encompasses most of the resolved energy and that the side load inducing mode is coherent with the response moment measured by strain gauges mounted upstream of the nozzle on a flexible tube. Finally, the unsteady pressure is locally more energetic during restricted shock separation, albeit direct measurements of the response moments indicate higher side load activity when in free shock separation state. It is postulated that these discrepancies are attributed to cancellation effects between annular separation bubbles.
Subject Aerodynamics (excl. Hypersonic Aerodynamics)
DOI - identifier 10.2514/1.J051075
Copyright notice Copyright © 2011 by W.J. Baars, C.E. Tinney, J.H. Ruf, A.M. Brown, and D.M. McDaniels
ISSN 0001-1452
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