Flow and acoustics of clustered rockets during startup

Citation:

A. Canchero, Tinney, C. E., Murray, N., and Ruf, J. H., “Flow and acoustics of clustered rockets during startup,” AIAA Journal, vol. 54, no. 5, pp. 1660-1669, 2016.

Abstract:

The plume produced by a cluster of two large area-ratio thrust-optimized parabolic
contour nozzles is visualized over a range of nozzle pressure ratios by way of retrore-
flective shadowgraphy. Both nozzles exhibit free-shock separated flow, restricted-shock
separated flow and an end-effects regime prior to flowing full. Transient (startup) op-
erations of the nozzles are studied with the primary focus being the pulsations that
form during the end-effects regime. This occurs at a pressure ratio of 37 for these
nozzles and is associated with elevated sound levels in the immediate vicinity of the
nozzles and vehicle. The shadowgraphy images reveal the formation of turbulent large
scale structures, on the order of the nozzle diameter, during the end-effects regime.
These large scale structures are driven by the intermittent opening of the last trapped
annular separation bubble to the ambient and grow rapidly within the first two nozzle
diameters.

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