Computational aeroacoustics beneath high speed transitional and turbulent boundary layers

Ritos, Konstantinos; Drikakis, Dimitris; Kokkinakis, Ioannis; Spottswood, S. Michael

doi:10.1016/j.compfluid.2020.104520

Cited by 19 publications

(7 citation statements)

References 61 publications

(78 reference statements)

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“…With the availability of ever more increasing computational power, high-order large eddy simulation (LES) has gradually started to become more feasible and widely adopted in industrial applications. Furthermore, highresolution and high-order methods for compressible flows featuring shock-waves and turbulence allow performing both implicit Large Eddy Simulations (iLES) and DNS in the same computational framework [1][2][3] .…”

Section: Introductionmentioning

confidence: 99%

Direct numerical simulation of supersonic flow and acoustics over a compression ramp

et al. 2020

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We present Direct Numerical Simulations (DNS) of shock turbulent boundary layers interaction (SBLI) at Mach 2.9 over a 24 • ramp. We study both the numerical accuracy and flow physics. Two classes of spatial reconstruction schemes are employed: the Monotonic Upstream centred Scheme for Conservation Laws (MUSCL) and the Weighted Essentially Non-Oscillatory (WENO), of accuracy ranging from 2 nd to 11 th-order. Using the canonical Taylor-Green vortex (TGV) test-case, a simple and computationally inexpensive rescaling of the candidate stencil values-within the context of the high-order WENO scheme-is proposed for reducing the numerical dissipation, particularly in underresolved simulations. For the compression ramp case, higher-order schemes are shown to capture the size of the SBLI separation zone more accurately, a consequence of resolving much finer turbulence structures. For second and fifthorder schemes, the energy of the unresolved small scale turbulence shifts the cascade of the turbulence kinetic energy spectrum, thus resulting in more energetic large scale turbulent structures. Consequently, the λ-shock foot shifts further downstream leading to a smaller separation bubble size. Nonetheless, other statistical quantities, such as the turbulence anisotropy invariant map and the turbulence kinetic energy budget terms, show little dependence on the type and order of the spatial reconstruction scheme. Finally, using the more accurate 9 th-order WENO results, it is reasoned that the interaction of the λ-shock with the post-shock relaxation region drives the low-frequency oscillation of the λ-shock.

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Section: Introductionmentioning

confidence: 99%

Direct numerical simulation of supersonic flow and acoustics over a compression ramp

et al. 2020

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“…The above is due to the non-linearity of these terms responsible for capturing transitional and turbulent flow features, as well as shock waves and contact discontinuities. CNS3D has been extensively validated against experimental and numerical results [29][30][31][32]44 .…”

Section: Computational Methodologymentioning

confidence: 99%

“…5. Comparison between iLES44 and DNS of a) shape factor H, b) skin friction C f , c) Stanton number St and d) Re θ along the plate. An empirical correlation (Eq.…”

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Flow transition to turbulence and induced acoustics at Mach 6

et al. 2021

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This paper presents the results of implicit Large Eddy Simulation (iLES) and Direct Numerical Simulation (DNS) for flow and acoustics for transitional and turbulent boundary layer over a flat plate at Mach 6. The DNS was about 50 times more refined grid-wise than iLES. Both DNS and iLES were performed using the same numerical schemes, initial and boundary conditions. We compare the different numerical approaches concerning the shape factor, momentumthickness-based Reynolds number, heat flux on the wall, Reynolds stress, and near-wall acoustics. We perform pressure fluctuations spectral analysis and propose a predictive model. We show that iLES captures pretty accurately the flow and acoustic characteristics in the turbulent region. Differences up to 5 dB occur between iLES and DNS in the transition region. iLES also shifts slightly further downstream the end of the transition and underpredicts the shear stress value peak. The iLES captures the near-wall acoustic spectrum roll-off accurately at low and medium frequencies. It underpredicts high frequencies' content due to grid constraints. Overall, iLES gives excellent results compared to the significantly more refined DNS. The results show that high-order numerical simulations can help adapt and validate semi-empirical models for the engineering design and acoustic loading on hypersonic structures.Flow transition to turbulence and induced acoustics at Mach 6

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“…Several experimental and numerical studies of high-speed, turbulent boundary layers have been published [1][2][3][4][5][6][7][8][9][10][11][12] . The above studies provide data that advance understanding of the flow processes and guide the design of engineering models.…”

Section: Introductionmentioning

confidence: 99%

Wavelet analysis of high-speed transition and turbulence over a flat surface

et al. 2022

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This paper presents a study of high speed boundary layers using the wavelet method. We analyze direct numerical simulation data for high-speed, compressible transitional, and turbulent boundary layer flows using orthogonal anisotropic wavelets. The wavelet-based method of extraction of coherent structures is applied to the flow vorticity field, decomposed into coherent and incoherent contributions using thresholding of the wavelet coefficients. We show that the coherent parts of the flow, enstrophy spectra, are close to the statistics of the total flow, and the energy of the incoherent, noise-like background flow is equidistributed. Furthermore, we investigate the distribution of the incoherent vorticity in the transition and turbulent regions and examine the correlation with the near-wall pressure fluctuations. The results of our analysis suggest that the incoherent vorticity part is not a random “noise” and correlates with the actual noise emanating from inside the boundary layer. This could have implications regarding our understanding of the physics of compressible boundary layers and the development of engineering models.

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Computational aeroacoustics beneath high speed transitional and turbulent boundary layers

Cited by 19 publications

References 61 publications

Direct numerical simulation of supersonic flow and acoustics over a compression ramp

Direct numerical simulation of supersonic flow and acoustics over a compression ramp

Flow transition to turbulence and induced acoustics at Mach 6

Wavelet analysis of high-speed transition and turbulence over a flat surface

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