Propagation characteristics of laser-induced acoustic sources in hybrid anechoic wind tunnels

Szőke, Máté; Devenport, William J.

doi:10.1016/j.jsv.2021.116294

Cited by 7 publications

(2 citation statements)

References 31 publications

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“…For a detailed description of the laser-optical set-up, experimental apparatus, and data processing procedures, see Szőke et al. (2022) and Szőke & Devenport (2021).…”

Section: Example Iv: Acoustic Signature Of Laser-induced Plasmamentioning

confidence: 99%

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Residual dynamic mode decomposition: robust and verified Koopmanism

2023

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Dynamic mode decomposition (DMD) describes complex dynamic processes through a hierarchy of simpler coherent features. DMD is regularly used to understand the fundamental characteristics of turbulence and is closely related to Koopman operators. However, verifying the decomposition, equivalently the computed spectral features of Koopman operators, remains a significant challenge due to the infinite-dimensional nature of Koopman operators. Challenges include spurious (unphysical) modes and dealing with continuous spectra, which both occur regularly in turbulent flows. Residual dynamic mode decomposition (ResDMD), introduced by Colbrook & Townsend (Rigorous data-driven computation of spectral properties of Koopman operators for dynamical systems. 2021. arXiv:2111.14889), overcomes such challenges through the data-driven computation of residuals associated with the full infinite-dimensional Koopman operator. ResDMD computes spectra and pseudospectra of general Koopman operators with error control and computes smoothed approximations of spectral measures (including continuous spectra) with explicit high-order convergence theorems. ResDMD thus provides robust and verified Koopmanism. We implement ResDMD and demonstrate its application in various fluid dynamic situations at varying Reynolds numbers from both numerical and experimental data. Examples include vortex shedding behind a cylinder, hot-wire data acquired in a turbulent boundary layer, particle image velocimetry data focusing on a wall-jet flow and laser-induced plasma acoustic pressure signals. We present some advantages of ResDMD: the ability to resolve nonlinear and transient modes verifiably; the verification of learnt dictionaries; the verification of Koopman mode decompositions; and spectral calculations with reduced broadening effects. We also discuss how a new ordering of modes via residuals enables greater accuracy than the traditional modulus ordering (e.g. when forecasting) with a smaller dictionary. This result paves the way for more significant dynamic compression of large datasets without sacrificing accuracy.

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“…For a detailed description of the laser-optical set-up, experimental apparatus, and data processing procedures, see Szőke et al. (2022) and Szőke & Devenport (2021).…”

Section: Example Iv: Acoustic Signature Of Laser-induced Plasmamentioning

confidence: 99%

“…During the experiments, 65 realisations of LIP are captured using microphones. Each realisation of LIP is then gated in time such that only the direct propagation path of the LIP remains in the signal (Szőke & Devenport 2021). We use this gated data for our ResDMD analysis.…”

Section: Example Iv: Acoustic Signature Of Laser-induced Plasmamentioning

confidence: 99%

Residual dynamic mode decomposition: robust and verified Koopmanism

2023

Self Cite

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Numerical Aeroacoustic Assessment of a Metacontinuum Device Impinged by a Laser‐Generated Sound Source

Colombo,

Palma,

Iemma

2024

Journal of Engineering

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Significant research efforts have been conducted by many research groups in the last decades to circumvent the acoustic metamaterial concept limitations. Principally, the lack of a reliable methodology for the design of such metamaterial‐based devices and their performance decay when they operate in a moving medium were the main topics of investigation that culminated in a number of possible approaches with a high potential of application in aeroacoustics. One of these approaches is based on the aeroacoustic spacetime reformulation of the problem to recast the governing equations in a generalized form, independent of the kinematic conditions of the supporting medium. In the present paper, the response of a spacetime‐corrected metacontinuum is coupled with a high‐fidelity aeroacoustic model of the hosting fluid to allow for the modelling of actual experimental realizations of a laser‐generated sound source. The availability of a reliable model to couple the convective metacontinuum design with the heat‐release source would make possible the systematic cross‐validation of the numerical simulations with the experimental results obtained in the most advanced testing facilities, paving the way to an effective inclusion of metacontinuum‐based devices in aeronautics and, finally, in a simulation‐based, multidisciplinary design optimization framework. Although the method presented is valid for arbitrary acoustic responses, the numerical simulations presented in this work have been conducted using the classic Cummer–Schurig inertial cloaking as a reference application, which can now be considered a widely accepted benchmark for acoustic metamaterial applications.

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Fluid–Structure Interaction Modeling of Flowfields Within Kevlar-Walled Wind Tunnels

Szőke

Borgoltz

Devenport

2022

Journal of Aircraft

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A detailed three-dimensional (3D) two-way coupled fluid–structure interaction simulation of a hybrid anechoic wind tunnel (HAWT) test section is presented with modeling all important effects, namely, turbulence, Kevlar wall porosity, and deflection. The complete 3D flowfield around a 3-ft chord NACA0012 placed into a HAWT test section is assessed. The Kevlar deflections are captured using finite element analysis, whereas 3D Reynolds-averaged Navier–Stokes computational fluid dynamics simulations are used to resolve the flowfield. Source terms are used to model the transpiration flow across the pores of the Kevlar fabric. Results are validated against an extensive experimental dataset. Aerodynamic properties of the airfoil are validated using airfoil pressure coefficients, airfoil wake pressure coefficients, and lift and drag coefficients. Boundary effects are validated against Kevlar wall pressure coefficients, Kevlar displacement, and transpiration velocity through the Kevlar fabric. Overall, a good agreement has been found among all comparisons presented. While some minor discrepancies were observed, these primarily stem from geometrical irregularities of the model and wind tunnel unresolved in the computational fluid dynamics. Overall, the fluid–structure interaction model now enables a detailed assessment of HAWTs to enhance their performance and can support experimental testing.

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Propagation characteristics of laser-induced acoustic sources in hybrid anechoic wind tunnels

Cited by 7 publications

References 31 publications

Residual dynamic mode decomposition: robust and verified Koopmanism

Residual dynamic mode decomposition: robust and verified Koopmanism

Numerical Aeroacoustic Assessment of a Metacontinuum Device Impinged by a Laser‐Generated Sound Source

Fluid–Structure Interaction Modeling of Flowfields Within Kevlar-Walled Wind Tunnels

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