Unsteady Shock Motions in an Over-Expanded Parabolic Rocket Nozzle

Verma, SB and Haidn, O (2014) Unsteady Shock Motions in an Over-Expanded Parabolic Rocket Nozzle. Aerospace Science and Technology, 39. pp. 48-71. ISSN 1270-9638

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Official URL: http://dx.doi.org/10.1016/j.ast.2014.08.003


An experimental investigation has been conducted to identify a flow condition in free shock separation that is found to contribute significantly towards the overall flow unsteadiness in a thrust optimized parabolic nozzle at certain operating conditions. Cold gas tests were conducted with a 1/10th scale, area-ratio 30 thrust optimized parabolic nozzle both under sea-level and high-altitude conditions. Although the latter tests showed absence of fully formed restricted shock separation at any operating condition unlike sea-level tests, the peak rms values at certain operating conditions were still seen to be considerably high and comparable with those experienced during flow transitions in sea-level tests. A detailed statistical analysis of the data revealed that the separated shear-layer in free shock separation condition can come in very close proximity to the nozzle wall but at no point of time randomly impinges on it. This sets the entire back-flow region into pressure fluctuations that is seen to increase the length of intermittent region as well as the overall flow unsteadiness considerably. This in turn is strictly dictated by the relative locations of the normal shock to the separation shock which induces the necessary momentum imbalance of flow across each of these shocks to move the separated shear layer within critical proximities of the nozzle wall. Beyond this critical limit, flow reattachment occurs and a transition from free shock separation to fully formed restricted shock separation occurs.

Item Type: Article
Additional Information: Copyright to this article belongs to M/s. Elsevier Science Ltd
Uncontrolled Keywords: Unsteady shock motion;Intermittency;TOP nozzle;Shear-layer proximity
Subjects: ASTRONAUTICS > Spacecraft Propulsion & Power
Depositing User: Ms. Alphones Mary
Date Deposited: 28 Sep 2015 03:25
Last Modified: 28 Sep 2015 03:25
URI: http://nal-ir.nal.res.in/id/eprint/12396

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