Three-dimensionality in shock/boundary layer interactions: a numerical and experimental investigation

Broslawski, Casey; Candler, Graham V.; Bowersox, Rodney D. W.

doi:10.2514/6.2020-3011

Cited by 4 publications

(3 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The spanwise perturbation velocity component, ũy , which was zero at the beginning of the simulation, attains a sinusoidally varying amplitude not only inside the separation bubble, as known from earlier work (e.g. Ginoux 1958;Theofilis et al 2000;Shvedchenko 2009;Dwivedi et al 2020), but also inside the separation and detached shock layers and the shear layers formed downstream of triple points. This result extends the findings of Tumuklu et al (2018aTumuklu et al ( ,b, 2019 in the two-dimensional counterpart of this configuration but, contrary to the two-dimensional limit, in the present three-dimensional environment the observed global instability is unstable with synchronised spanwise-periodic small-amplitude perturbations amplifying exponentially within both the LSB and shock layer.…”

Section: Analysis Of the Three-dimensional Dsmc Signalsupporting

confidence: 59%

“…Compressibility may alter the relative significance of the two scenarios quantitatively, but not qualitatively. In this context, the interpretation of the experiments of Simeonides (1992) and the direct numerical simulations (DNS) work of Navarro-Martinez & Tutty (2005) would fall in the first category of a bubble acting as an amplifier, while the DNS of Shvedchenko (2009) and Egorov et al (2011), the global instability analysis of Dwivedi et al (2019) as well as the combined analysis and experiments of Dwivedi et al (2020) and Hao et al (2021) on the compression corner and the global instability analyses of Robinet (2007), Nichols et al (2017) and Hildebrand et al (2018) in the related problem of shock-generated laminar separation on a flat plate would be examples of the oscillator scenario.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On the synchronisation of three-dimensional shock layer and laminar separation bubble instabilities in hypersonic flow over a double wedge

2022

View full text Add to dashboard Cite

Linear three-dimensional instability is studied in the shock layer and the laminar separation bubble (LSB) induced by shock-wave/boundary-layer interactions in a Mach 7 flow of nitrogen over a double wedge with a $30^{\circ }\text {--}55^{\circ }$ cross-sectional profile. At a free-stream unit Reynolds number $Re=5.2\times 10^{4}\,{\rm m}^{-1}$ this flow exhibits rarefaction effects and has shock thicknesses comparable to the thickness of the boundary layer at separation. Flow features have been fully resolved using a high-fidelity massively parallel implementation of the direct simulation Monte Carlo method that captures the flow evolution from the inception of three-dimensionality, through linear growth of instabilities, to the early stages of nonlinear saturation. It is shown that the LSB sustains self-excited, small-amplitude perturbations that originate past the primary separation line and lead to spanwise-periodic wall striations inside the bubble and downstream of the primary reattachment line, as known from earlier experiments, simulations and instability analyses. A spanwise-periodic instability, synchronised with that in the separation zone, is identified herein for the first time, which exists in the internal structure of the separation and detached shock layers, and manifests itself as spanwise-periodic cats-eyes patterns in the global mode amplitude functions. The growth rate and the spanwise-periodicity length of linear disturbances in the shock layers and the LSB are found to be identical. Linear amplification of the most unstable three-dimensional flow perturbations leads to synchronised low-frequency unsteadiness of the triple point, with a Strouhal number of $St\approx 0.028$ .

show abstract

Section: Analysis Of the Three-dimensional Dsmc Signalsupporting

confidence: 59%

Section: Introductionmentioning

confidence: 99%

On the synchronisation of three-dimensional shock layer and laminar separation bubble instabilities in hypersonic flow over a double wedge

2022

View full text Add to dashboard Cite

show abstract

“…The resulting flow is characterized by separation-reattachment shocks as well as a recirculation zone and it provides a canonical set-up for studying shock-wave-boundary-layer interaction (SWBLI) (Simeonides & Haase 1995). In spite of spanwise homogeneity of laminar base flows over compression corners, both experiments Roghelia et al 2017;Dwivedi et al 2020a) and numerical simulations (Navarro-Martinez & Tutty 2005;Dwivedi et al 2017;Cao et al 2021b) identify three-dimensional (3-D) features in time-averaged separated flows. In particular, streamwise streaks associated with persistent local peaks of heat flux or wall temperature, that appear near reattachment, can trigger transition to turbulence downstream (Simeonides & Haase 1995;Roghelia et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Oblique transition in hypersonic double-wedge flow

Sidharth

Jovanović

2022

J. Fluid Mech.

Self Cite

View full text Add to dashboard Cite

We utilize resolvent and weakly nonlinear analyses in combination with direct numerical simulations (DNS) to identify mechanisms for oblique transition in a Mach $5$ hypersonic flow over an adiabatic slender double wedge. Even though the laminar separated flow is globally stable, resolvent analysis demonstrates significant amplification of unsteady external disturbances to the linearized flow equations. These disturbances are introduced upstream of the separation zone and they lead to the appearance of oblique waves further downstream. We demonstrate that the large amplification of oblique waves arises from the growth of fluctuation shear stress due to streamline curvature of the laminar base flow in the separated shear layer. This is in contrast to the attached boundary layers, where no such mechanism exists. We also use a weakly nonlinear analysis to show that the resolvent operator associated with linearization around the laminar base flow governs the evolution of steady reattachment streaks that arise from quadratic interactions of unsteady oblique waves. These quadratic interactions generate vortical excitations in the reattaching shear layer which lead to the formation of streaks in the recirculation zone and their subsequent amplification, breakdown and transition to turbulence downstream. Our analysis of the energy budget shows that deceleration of the base flow near reattachment is primarily responsible for amplification of steady streaks. Finally, we employ DNS to examine latter stages of transition to turbulence and demonstrate the predictive power of a weakly nonlinear input–output framework in uncovering triggering mechanisms for oblique transition in separated high-speed boundary layer flows.

show abstract