Global linear stability analysis of high speed flows on compression ramps

Sidharth, G. S.; Candler, Graham V.; Nichols, Joseph W.

doi:10.2514/6.2017-3455

Cited by 5 publications

(1 citation statement)

References 21 publications

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“…While there have been many experimental and numerical investigations of shock waves interacting with both laminar [2][3][4][5][6][7] and turbulent [8][9][10][11][12][13][14][15][16][17][18][19] boundary layers, studies of shock waves interacting with boundary layers at transitional Reynolds numbers are relatively sparse. Interactions with hypersonic boundary layers at transitional Reynolds numbers can produce complex and unexpected behavior.…”

Section: Introductionmentioning

confidence: 99%

Simulation and stability analysis of oblique shock-wave/boundary-layer interactions at Mach 5.92

et al. 2018

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We investigate flow instability created by an oblique shock wave impinging on a Mach 5.92 laminar boundary layer at a transitional Reynolds number. The adverse pressure gradient of the oblique shock causes the boundary layer to separate from the wall, resulting in the formation of a recirculation bubble. For sufficiently large oblique shock angles, the recirculation bubble is unstable to three-dimensional perturbations and the flow bifurcates from its original laminar state. We utilize Direct Numerical Simulation (DNS) and Global Stability Analysis (GSA) to show that this first occurs at a critical shock angle of θ = 12.9• . At bifurcation, the least stable global mode is nonoscillatory, and it takes place at a spanwise wavenumber β = 0.25, in good agreement with DNS results. Examination of the critical global mode reveals that it originates from an interaction between small spanwise corrugations at the base of the incident shock, streamwise vortices inside the recirculation bubble, and spanwise modulation of the bubble strength. The global mode drives the formation of long streamwise streaks downstream of the bubble. While the streaks may be amplified by either the lift-up effect or by Görtler instability, we show that centrifugal instability plays no role in the upstream self-sustaining mechanism of the global mode. We employ an adjoint solver to corroborate our physical interpretation by showing that the critical global mode is most sensitive to base flow modifications that are entirely contained inside the recirculation bubble.

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