On low-frequency unsteadiness in swept shock wave–boundary layer interactions

Ceci, Alessandro; Palumbo, Andrea; Larsson, Johan; Pirozzoli, Sergio

doi:10.1017/jfm.2023.2

Cited by 15 publications

(4 citation statements)

References 34 publications

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“…The prediction is clearly quite good, perhaps with exception of the single data point corresponding to γ0 = 30 • , θ = 8 • , which has a small separation bubble. Overall, the agreement becomes more satisfactory as the sweep angle increases [6].…”

Section: Results Of the Supersonic Sbli Studymentioning

confidence: 76%

High-fidelity simulation of shock-wave/boundary layer interactions

Ceci

2023

Materials Research Proceedings

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Abstract. We perform direct numerical simulations of impinging shock-boundary layer interaction on a flat plate, in which the shock is not orthogonal to the boundary layer flow. The analysis relies on an idealized configuration, where a spanwise flow component is used to introduce the effect of the sweep angle between a statistically two-dimensional boundary layer and the shock. A quantitative comparison is carried out between the swept case and the corresponding unswept one, and the effect of the domain spanwise width is examined. The analysis reveals that, while the time-averaged swept flow characteristics are basically unaffected by the choice of the domain width, the spectral dynamics of the flow dramatically changes with it. For very narrow domains, a pure two-dimensional, low-frequency component can be detected, which resembles the low-frequency oscillation of the unswept case. The present work is also devoted to compare the performance of Digital Filtering (DF) and Recycling-Rescaling methods (RR) in reaching an equilibrium state for the Direct Numerical Simulation (DNS) of a turbulent boundary layer. We performed two sets of DNS of supersonic and hypersonic boundary layers, based on previous numerical studies. It is found that, overall, the RR method is the most appropriate choice, to quickly reach a correct trend of the wall pressure fluctuations, whereas the DF method is more capable in obtain small deviations of the skin friction coefficient with respect to the benchmark.

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Section: Results Of the Supersonic Sbli Studymentioning

confidence: 76%

High-fidelity simulation of shock-wave/boundary layer interactions

Ceci

2023

Materials Research Proceedings

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“…Recently, Ceci et al. (2023) have proposed that the typical frequencies increase with the skew angle, on account of propagation spanwise travelling disturbances. Figure 15 shows evidence for 2-D-like dynamics in the proximity of the separation and reattachment points, as well as in the secondary APG region.…”

Section: Characterization Of Wall Pressure Fluctuationsmentioning

confidence: 99%

“…Cases under consideration cover a large range of geometric configurations, including impinging planar shocks (Dupont et al 2006;Robinet 2007;Humble et al 2009;Piponniau et al 2009;Pirozzoli & Bernardini 2011a;Touber & Sandham 2011;Sandham et al 2014;Pasquariello, Hickel & Adams 2017;Lusher & Sandham 2020), over-expanded nozzles (Martelli et al 2017), compression ramps (Adams 2000;Ganapathisubramani, Clemens & Dolling 2007;Wu & Martin 2008;Priebe & Martin 2012;Exposito, Gai & Neely 2021;Helm, Martin & Williams 2021) and transonic normal shock waves (Pirozzoli, Bernardini & Grasso 2010;Burton & Babinsky 2012;Sartor et al 2015;Karnick & Venkatraman 2017). Despite the efforts of the research community, the physical mechanisms involved in SBLIs are not yet completely understood, especially concerning the low-frequency unsteadiness associated with the separation shock, whose frequencies are approximately two orders of magnitude lower than those of the upstream boundary layer, and whose underlying cause is still debated (Priebe et al 2016;Adler & Gaitonde 2020;Ceci et al 2023;Gaitonde & Adler 2023).…”

Section: Introductionmentioning

confidence: 99%

On wall pressure fluctuations in conical shock wave/turbulent boundary layer interaction

2023

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The structure and the frequency spectra of wall pressure fluctuations beneath a planar turbulent boundary layer interacting with a conical shock wave at Mach number $M_\infty =2.05$ and Reynolds number $\textit {Re}_\theta \approx 630$ (based on the upstream boundary layer momentum thickness) are examined to elucidate the effects of pressure gradient and flow separation on the characteristics of the wall pressure fluctuations, by exploiting a direct numerical simulation database. Upstream of the interaction, in the zero pressure gradient region, wall pressure statistics compare well with canonical compressible boundary layers in terms of fluctuation intensities and frequency spectra. Across the main interaction zone (APG1), the root-mean-square of wall pressure fluctuations becomes very large (corresponding to approximately 173.3 dB), with maximum increase approximately 12.7 dB from the incoming level. In the second adverse pressure gradient zone (APG2), the root-mean-square of wall pressure fluctuations attains a second peak (corresponding to $164.7$ dB), with an increase of 8.4 dB from the upstream level. Both the APG1 and APG2 regions feature a substantial fraction of flow reversal events, which are, however, scattered and interspersed with regions of attached flow. The wall pressure power spectral density exhibits a broadband and energetic low-frequency component associated with the global unsteadiness of the separation bubble/conical shock system. Analysis of the two-point correlations and wavenumber/frequency spectra of wall pressure fluctuations further suggests that the typical eddies become more elongated along the spanwise direction, as the flow in the separated region tends to escape the centreline, and the convection velocity is significantly reduced.

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“…A modular Python implementation of the proposed stretching is available on the github repository HYPERGRID [37]. The original modules used to compute the boundary layer profiles can be found at the web page https://larsson .umd .edu /code/ (compressibleBLprofiles).…”

Section: Credit Authorship Contribution Statementmentioning

confidence: 99%