Numerical Simulation of Transition in Hypersonic Boundary Layers

Fasel, Hermann F.; Groß, Andreas; Koevary, Clayton; Laible, Andreas C.; Mayer, Christine; Sivasubramanian, Jayahar

doi:10.21236/ada563832

Cited by 3 publications

(1 citation statement)

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“…Even though the DNS results validate the predictions of our analysis, other mechanisms for streak formation are possible. For example, it is well known that unsteady oblique modes can interact nonlinearly to produce streaks in canonical flows (Schmid & Henningson 1992;Berlin et al 1994;Fasel et al 1993;Sandham et al 1995;Chang & Malik 1994). However, even when we conduct simulations using a pair of unsteady oblique inputs (shown in figure 5(c) and with the same amplitude as the previous steady inputs), the dominant responses in DNS are still given by the steady streaky outputs.…”

Section: Validation Of Dominant Output Directions Using Dnsmentioning

confidence: 98%

Reattachment streaks in hypersonic compression ramp flow: an input–output analysis

Dwivedi¹,

Sidharth

Nichols³

et al. 2019

J. Fluid Mech.

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We employ global input-output analysis to quantify amplification of exogenous disturbances in compressible boundary layer flows. Using the spatial structure of the dominant response to time-periodic inputs, we explain the origin of steady reattachment streaks in a hypersonic flow over a compression ramp. Our analysis of the laminar shock/boundary layer interaction reveals that the streaks arise from a preferential amplification of upstream counter-rotating vortical perturbations with a specific spanwise wavelength. These streaks are associated with heat flux striations at the wall near flow reattachment and they can trigger transition to turbulence. The streak wavelength predicted by our analysis compares favorably with observations from two different hypersonic compression ramp experiments. Furthermore, our analysis of inviscid transport equations demonstrates that base flow deceleration contributes to the amplification of streamwise velocity and that the baroclinic effects are responsible for the production of streamwise vorticity. Finally, the appearance of the temperature streaks near reattachment is triggered by the growth of streamwise velocity and streamwise vorticity perturbations as well as by the amplification of upstream temperature perturbations by the reattachment shock.

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