Scaling of pseudoshock length and pressure rise

Hunt, Robin L.; Edelman, Louis M.; Gamba, Mirko

doi:10.2514/6.2018-1617

Cited by 9 publications

(2 citation statements)

References 9 publications

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“…The goal of the experiment is to measure number density (N) and temperature (T) of an isolator shock train flow field. This challenging flow field contains a supersonic, shock-dominated core flow surrounded by turbulent boundary layers with large separation regions [34,35]. The flow field is contained in a constant area rectangular duct that mimics the isolator section of a high-speed air-breathing engine, where a shock train is found in real life application.…”

Section: Motivating Application: Filtered Rayleigh Scattering Of a Sh...mentioning

confidence: 99%

“…The red shaded region indicates the range of frequencies over which the central frequency of the incident laser is varied for our parametric study. [34,35]. To complicate matters further, the shock train moves in response to changing inflow conditions from the inlet or downstream combustor conditions.…”

Section: Optimization Of An Frs Experiments Of a Complex Flow-fieldmentioning

confidence: 99%

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Fast approximations of spectral lineshapes to enable optimization of a filtered Rayleigh scattering experiment

Hunt

Ground

Hunt

2020

Meas. Sci. Technol.

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Measuring the properties of scattered light is central to many laser-based gas diagnostic techniques, such as filtered Rayleigh scattering (FRS). Alongside the measurements, a model of the scattered light’s spectral lineshape is often used to extract quantitative information about the flow field like pressure, temperature, and velocity. In particular, the Tenti S6 or S7 model are frequently used to model the lineshape of Rayleigh–Brillouin (RB) scattered light. While accurate, it is well attested in the literature that these models can be computationally expensive when evaluated many times, for example, as part of iterative estimation or optimization routines. To overcome this, approximations of these spectral lineshape models can be used instead. In this paper, we develop a method called support vector spectrum approximation (SVSA). This method uses support vector regression and singular value decomposition to create efficient, accurate, and well-conditioned approximations of any existing spectral lineshape model. The SVSA framework improves upon existing approximation methods by allowing quick calculation of spectral lineshapes for arbitrary flow regimes with any number of input parameters over a wide range of values. We demonstrate the efficacy of SVSA in approximating coherent and spontaneous RB scattering spectra. In application, we use SVSA to optimize the design of a filtered Rayleigh scattering experiment of a complex shock-dominated flow. SVSA allows us to comprehensively minimize expected measurement uncertainty of number density and temperature for this experiment. It does this by enabling a high-resolution design of experiments that is otherwise intractable.

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Section: Motivating Application: Filtered Rayleigh Scattering Of a Sh...mentioning

confidence: 99%

Section: Optimization Of An Frs Experiments Of a Complex Flow-fieldmentioning

confidence: 99%

Fast approximations of spectral lineshapes to enable optimization of a filtered Rayleigh scattering experiment

Hunt

Ground

Hunt

2020

Meas. Sci. Technol.

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Simple Physics-Based Model for the Prediction of Shock-Train Location

Vanstone

Lingren

Clemens

2018

Journal of Propulsion and Power

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

Edelman¹,

Gamba²,

Hunt³

et al. 2023

Journal of Propulsion and Power

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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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Scaling of pseudoshock length and pressure rise

Cited by 9 publications

References 9 publications

Fast approximations of spectral lineshapes to enable optimization of a filtered Rayleigh scattering experiment

Fast approximations of spectral lineshapes to enable optimization of a filtered Rayleigh scattering experiment

Simple Physics-Based Model for the Prediction of Shock-Train Location

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

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