A highly confined shock train is investigated in a direct-connect isolator facility with a Mach 2 inflow and a constant-area low-aspect-ratio rectangular test section. High-speed schlieren imaging, wall static pressure measurements, surface oil-flow visualization, and particle image velocimetry from this isolator are synthesized into a three-dimensional schematic of the shock train structure. Against this, the prevailing pseudoshock models in the literature are assessed to evaluate the validity of their underlying assumptions. None of the prevailing pseudoshock models are found to simultaneously model the pressure and Mach number profiles, indicating a gap in the model formation and underlying assumptions when applied to the experimental isolator of interest. The presence of distortion in the isolator flowfield, such as a wall-bounded vortex, is found to skew the structure of the shock train, altering the strength and distribution of the compressive pressure gradient. It is further observed that the separated flow morphology surrounding the shock train is not monolithic, as is typically assumed, adjusting the balance of compressive forces within the shock cells. These findings lead to the conclusion that existing flux-conserved modeling approaches require modification to be effective in distorted and highly confined cases, including closure models that capture the three-dimensional distorted structure of the approach flow and its evolution along the shock train.

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Volume 39, Number 5September 2023

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Louis Edelman acknowledges the financial support of the Office of Naval Research through the National Defense Science and Engineering Graduate Fellowship program and the continued support of the NASA Langley Research Center Flow Physics and Control, Hypersonic Airbreathing Propulsion, and Supersonic/Hypersonic Testing branches.

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Received24 May 2022
Accepted23 April 2023
Published online10 June 2023

Assessment of Pseudoshock Models Against Experiment in a Low-Aspect-Ratio Isolator

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