Two-dimensional numerical investigations of small-amplitude disturbances in a boundary layer at Ma=4.8: Compression corner versus impinging shock wave

Pagella, Alessandro; Babucke, Andreas; Rist, Ulrich

doi:10.1063/1.1738414

Cited by 29 publications

(14 citation statements)

References 5 publications

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“…A 2D case is run for a 6 • compression ramp at M = 4.8 and Re = 6, 843. Good agreement is obtained with Ludeke and Sandham [3] and Pagella et al [5]. Simulations are then run in 2D at 12 • at M = 4.8 and Re=3,422 and 6,843.…”

Section: Resultssupporting

confidence: 75%

Instability of Supersonic Ramp Flow with Intermittent Transition to Turbulence

Zhang

Sandham

2017

Direct and Large-Eddy Simulation X

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This paper investigates the global instability of supersonic ramp flow at Mach number 4.8 at different Reynolds numbers through direct numerical simulations. It is found that a critical Reynolds number exist for the flow to become globally unstable. Transition to turbulent happens downstream of the ramp with strong intermittency and is due to the breakdown of streaky structures fed by instability from the ramp separation region.

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Section: Resultssupporting

confidence: 75%

Instability of Supersonic Ramp Flow with Intermittent Transition to Turbulence

Zhang

Sandham

2017

Direct and Large-Eddy Simulation X

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“…Pagella et al 27 investigated the differences between a compression corner and a laminar boundary layer with impinging shock wave and found (a) the two configurations to be identical apart from near the corner and the impinging shock and (b) good agreement between the LST and DNS approaches, albeit for weaker interaction than those considered here. For the present study, the amplitude of the disturbances at different x-locations are normalised with the amplitude at the separation point allowing a direct comparison between DNS and LST.…”

Section: Resultsmentioning

confidence: 66%

Stability and Unsteadiness in a 2D Laminar Shock-Induced Separation Bubble

Sansica

Sandham

2013

43rd Fluid Dynamics Conference

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A computational study of the interaction between an oblique shock-wave and a laminar boundary-layer on a flat plate is carried out to investigate the unsteady character of a two-dimensional (2D) separation bubble at a free-stream Mach number of 1.5. In order to validate the code, a review of the case is presented, highlighting some significant differences compared to previous works that were not run sufficiently far in time. A steady base flow is forced with white noise and a global analysis is carried out to investigate the response of the shockinduced separation bubble. An amplitude sensitivity study is carried out for two different forcing locations, one upstream and one within the separation bubble. Independently of the forcing location all the spectra show a high frequency peak, which is demonstrated to be a Kelvin-Helmholtz instability by the linear e N -method, and an unsteady low-frequency behaviour. For low amplitude forcing applied within the bubble the low-frequency response is linear. For upstream forcing the low-frequency response is driven by the non-linearity of the downstream shedding. The same phenomenon occurs when downstream forcing is applied over a narrow band that does not include low frequencies. The occurrence of low-frequency unsteadiness in a 2D laminar problem shows the possibility to link recent works on turbulent interaction back to simpler laminar problems. In particular it is shown that the low-frequency occurs in the absence of upstream disturbances and that it can be effectively driven by broadband disturbances within the separation bubble, for example arising from weakly non-linear interaction of shear-layer modes instability.

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“…In this work, the response of the initially laminar boundary layer to artificially introduced smallamplitude disturbances was investigated and the results compared well with those of linear stability theory. This work was later extended to the case of a 2D compression ramp flow, also at Mach 4.8 ͑Pagella et al 15 ͒, showing that, when the impinging shock and the shock created by the compression ramp have the same strength, the characteristics of SBLI were identical ͑validating the so-called free interaction concept originated by Chapman et al 16 ͒. This latter work also demonstrated that the response to small-amplitude disturbances was practically identical.…”

Section: Introductionmentioning

confidence: 88%

The effect of Mach number on unstable disturbances in shock/boundary-layer interactions

et al. 2007

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The effect of Mach number on the growth of unstable disturbances in a boundary layer undergoing a strong interaction with an impinging oblique shock wave is studied by direct numerical simulation and linear stability theory ͑LST͒. To reduce the number of independent parameters, test cases are arranged so that both the interaction location Reynolds number ͑based on the distance from the plate leading edge to the shock impingement location for a corresponding inviscid flow͒ and the separation bubble length Reynolds number are held fixed. Small-amplitude disturbances are introduced via both white-noise and harmonic forcing and, after verification that the disturbances are convective in nature, linear growth rates are extracted from the simulations for comparison with parallel flow LST and solutions of the parabolized stability equations ͑PSE͒. At Mach 2.0, the oblique modes are dominant and consistent results are obtained from simulation and theory. At Mach 4.5 and Mach 6.85, the linear Navier-Stokes results show large reductions in disturbance energy at the point where the shock impinges on the top of the separated shear layer. The most unstable second mode has only weak growth over the bubble region, which instead shows significant growth of streamwise structures. The two higher Mach number cases are not well predicted by parallel flow LST, which gives frequencies and spanwise wavenumbers that are significantly different from the simulations. The PSE approach leads to good qualitative predictions of the dominant frequency and wavenumber at Mach 2.0 and 4.5, but suffers from reduced accuracy in the region immediately after the shock impingement. Three-dimensional Navier-Stokes simulations are used to demonstrate that at finite amplitudes the flow structures undergo a nonlinear breakdown to turbulence. This breakdown is enhanced when the oblique-mode disturbances are supplemented with unstable Mack modes.

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Two-dimensional numerical investigations of small-amplitude disturbances in a boundary layer at Ma=4.8: Compression corner versus impinging shock wave

Cited by 29 publications

References 5 publications

Instability of Supersonic Ramp Flow with Intermittent Transition to Turbulence

Instability of Supersonic Ramp Flow with Intermittent Transition to Turbulence

Stability and Unsteadiness in a 2D Laminar Shock-Induced Separation Bubble

The effect of Mach number on unstable disturbances in shock/boundary-layer interactions

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