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Investigation of shock dynamics in an axisymmetric inlet/isolator with attached boundary layers

Published online by Cambridge University Press:  15 December 2020

Michael D. Leonard  and
V. Narayanaswamy Open the ORCID record for V. Narayanaswamy [Opens in a new window]
Michael D. Leonard
Affiliation:
Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC27695, USA
V. Narayanaswamy*
Affiliation:
Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC27695, USA
*
†Email address for correspondence: vnaraya3@ncsu.edu
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Abstract

Shock oscillations within a model two-dimensional axisymmetric inlet with a constant area isolator are investigated under the condition of maintaining an unseparated boundary layer throughout the inlet/isolator section. Power spectral densities of the wall-pressure fluctuations beneath each shock leg intersecting the isolator surface exhibited a very low frequency broadband oscillation in the 10–100 Hz range as well as a very high frequency broadband oscillations above 10 kHz. Whereas the high frequency oscillations are attributed to the incoming boundary layer fluctuations, detailed investigations into the pressure fluctuation communication pathways within the isolator and their length scale of communication are made to elucidate the origin of the low frequency fluctuations. It was found that the downstream propagation of pressure fluctuations is primarily by the convection of the boundary layer structures and this communication occurred over several boundary layer thicknesses. The upstream propagation occurs through acoustic waves that extend over a distance of one local boundary layer thickness. Based on this understanding, a physical model is constructed, which makes an accurate prediction of pressure power spectrum of the low frequency shock wave oscillations; the model predictions also favourably compare with the shock oscillations in external shock boundary layer interactions without shock-induced flow separation.

JFM classification

Aerodynamics: High-speed flow Compressible Flows: Compressible boundary layers Compressible Flows: Shock waves
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 908 , 10 February 2021 , A42
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Copyright
© The Author(s), 2020. Published by Cambridge University Press

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