Transitional shockwave/boundary layer interaction experiments in the R2Ch blowdown wind tunnel

Lugrin, Mathieu; Nicolas, F.; Severac, Nicolas; Tobeli, Jean-Pierre; Beneddine, Samir; Garnier, Éric; Esquieu, Sebastien; Bur, Reynald

doi:10.1007/s00348-022-03395-9

Cited by 15 publications

(9 citation statements)

References 47 publications

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“…Benay et al (2006) performed an experimental study of a Mach 5 hollow-cylinder/flare flow and observed periodic and steady streamwise streaks near flow reattachment using surface oil-flow visualization with various Reynolds numbers. As a continuation, similar experiments were recently performed by Lugrin et al (2022) at Mach 5 with three different Reynolds numbers. They observed streamwise streaks with different wavenumbers near reattachment and oblique modes travelling in the shear layer above the recirculation zone using a spectral proper orthogonal decomposition of surface infrared and high-speed schlieren images.…”

Section: Introductionmentioning

confidence: 77%

“…As a continuation, similar experiments were recently performed by Lugrin et al . (2022) at Mach 5 with three different Reynolds numbers. They observed streamwise streaks with different wavenumbers near reattachment and oblique modes travelling in the shear layer above the recirculation zone using a spectral proper orthogonal decomposition of surface infrared and high-speed schlieren images.…”

Section: Introductionmentioning

confidence: 99%

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Global stability of supersonic flow over a hollow cylinder/flare

Li,

Hao

2023

J. Fluid Mech.

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Supersonic flow over a hollow cylinder/flare with a free-stream Mach number of 2.25 is numerically investigated in this study. Axisymmetric computational fluid dynamics simulations and global stability analysis (GSA) are performed for a wide range of cylinder radii and flare deflection angles. The onset of incipient and secondary separation is delayed as the cylinder radius is decreased due to the axisymmetric effects. The GSA reveals that a decrease in cylinder radius also postpones the emergence of global instability. The GSA results agree well with the results of direct numerical simulations for a supercritical case in the linear stage. The saturated flow exhibits pairs of unsteady streamwise streaks downstream of reattachment. The criterion of the global stability boundary established for supersonic flow over a compression corner (Hao et al., J. Fluid Mech, vol. 919, 2021, A4) is extended to its axisymmetric counterpart.

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Section: Introductionmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Global stability of supersonic flow over a hollow cylinder/flare

Li,

Hao

2023

J. Fluid Mech.

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“…This choice is supported by the fact that second Mack modes exhibit strong pressure fluctuations close to the wall, as shown by the optimal response profiles in figure 3(g). Also, that kind of sensor is commonly used in supersonic experimental studies (Lugrin et al 2022).…”

Section: Selecting Actuator and Sensorsmentioning

confidence: 99%

Reactive control of second Mack mode in a supersonic boundary layer with free-stream velocity/density variations

et al. 2023

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We consider closed-loop control of a two-dimensional supersonic boundary layer at $M=4.5$ that aims at reducing the linear growth of second Mack mode instabilities. These instabilities are first characterized with local spatial and global resolvent analyses, which allow us to refine the control strategy and to select appropriate actuators and sensors. After linear input–output reduced-order models have been identified, multi-criteria structured mixed $H_{2}$ / $H_{\infty }$ synthesis allows us to fix beforehand the controller structure and to minimize appropriate norms of various transfer functions: the $H_{2}$ norm to guarantee performance (reduction of perturbation amplification in nominal condition), and the $H_{\infty }$ norm to maintain performance robustness (with respect to sensor noise) and stability robustness (with respect to uncertain free-stream velocity/density variations). Both feedforward and feedback set-ups, i.e. with estimation sensor placed respectively upstream/downstream of the actuator, allow us to maintain the local perturbation energy below a given threshold over a significant distance downstream of the actuator, even in the case of noisy estimation sensors or free-stream density variations. However, the feedforward set-up becomes completely ineffective when convective time delays are altered by free-stream velocity variations of $\pm$ 5 %, which highlights the strong relevance of the feedback set-up for performance robustness in convectively unstable flows.

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“…The next year, Lugrin et al. (2022) published their experimental findings on a hollow cylinder-flare with a sharp leading edge at the R2Ch blowdown tunnel at ONERA. Using heat transfer measurements, they observed clear streaks under the reattached boundary layer at various wavenumbers.…”

Section: Introductionmentioning

confidence: 99%

“…Utilizing spectral proper orthogonal decomposition (SPOD), they determined that transition on that geometry was caused by the linear amplification of oblique modes that interact nonlinearly, creating the streamwise striations observed frequently in experiments. The next year, Lugrin et al (2022) published their experimental findings on a hollow cylinder-flare with a sharp leading edge at the R2Ch blowdown tunnel at ONERA. Using heat transfer measurements, they observed clear streaks under the reattached boundary layer at various wavenumbers.…”

Section: Introductionmentioning

confidence: 99%

Instability and transition onset downstream of a laminar separation bubble at Mach 6

et al. 2023

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Instability measurements of an axisymmetric, laminar separation bubble were made over a sharp cone-cylinder-flare with a $12^{\circ }$ flare angle under hypersonic quiet flow. Two distinct instabilities were identified: Mack's second mode (which peaked between 190 and 290 kHz) and the shear-layer instability in the same frequency band as Mack's first mode (observed between 50 and 150 kHz). Both instabilities were measured with surface pressure sensors and were captured with high-speed schlieren. Linear stability analysis results agreed well with these measured instabilities in terms of both peak frequencies and amplification rates. Lower-frequency fluctuations were also noted in the schlieren data. Bicoherence analysis revealed nonlinear phase-locking between the shear-layer and second-mode instabilities. For the first time in axisymmetric, low-disturbance flow, naturally generated intermittent turbulent spots were observed in the reattached boundary layer. These spots appeared to evolve from shear-layer-instability wave packets convecting downstream. This work presents novel experimental evidence of the hypersonic shear-layer instability contributing directly to transition onset for an axisymmetric model.

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Transitional shockwave/boundary layer interaction experiments in the R2Ch blowdown wind tunnel

Cited by 15 publications

References 47 publications

Global stability of supersonic flow over a hollow cylinder/flare

Global stability of supersonic flow over a hollow cylinder/flare

Reactive control of second Mack mode in a supersonic boundary layer with free-stream velocity/density variations

Instability and transition onset downstream of a laminar separation bubble at Mach 6

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