Instability Measurements on an Axisymmetric Separation Bubble at Mach 6

Benitez, Elizabeth K.; Esquieu, Sebastien; Jewell, Joseph S.; Schneider, Steven P.

doi:10.2514/6.2020-3072

Cited by 32 publications

(15 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…separation length and unsteadiness) and thermomechanical surface loading (Heffner, Chpoun & Lengrand 1993;Benay et al 2006;Running et al 2018). Benitez et al (2020) employed focused laser differential interferometry (FLDI) to interrogate the separated boundary layer on a cone-cylinder-flare model. Low-frequency (50-170 kHz) travelling waves were identified downstream of the compression corner under quiet flow conditions, but could not be located within the separation region.…”

Section: Introductionmentioning

confidence: 99%

Interaction of second-mode disturbances with an incipiently separated compression-corner flow

Butler

Laurence

2021

J. Fluid Mech.

View full text Add to dashboard Cite

show abstract

Section: Introductionmentioning

confidence: 99%

Interaction of second-mode disturbances with an incipiently separated compression-corner flow

Butler

Laurence

2021

J. Fluid Mech.

View full text Add to dashboard Cite

show abstract

“…However, Lele (2013, 2014) have shown that oblique first mode instabilities may also play an important role in the transition process. The separated region may also bring new transitional mechanisms; for instance, recent experiments from Benitez et al (2020) have shown that the shear layer generates new instabilities. Those three-dimensional shearlayer oblique supersonic type instabilities may become the dominant linear instability above the separated region (Sandham and Reynolds, 1990;Reynolds, 1991;Kudryavtsev and Khotyanovsky, 2005;Foysi and Sarkar, 2010).…”

mentioning

confidence: 99%

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

et al. 2022

Self Cite

View full text Add to dashboard Cite

Transitional Shockwave/Boundary Layer Interactions (SBLI) is studied experimentally. Experiments are conducted on a hollow-cylinder flare model in the R2Ch blowdown facility at a Mach number of 5 for three different Reynolds numbers in the transitional regime. Unsteady wall pressure measurements are conducted along with mean and unsteady heat flux measurements and high-speed Schlieren imaging. The images are then processed using Proper Orthogonal Decomposition (POD) and Spectral Proper Orthogonal Decomposition (SPOD) to extract relevant information. Two main phenomena are identified and documented: the oblique modes traveling in the shear layer above the recirculation region and the streaks appearing in the reattachment region. New results illustrating the multiple physical origins of the streaks, either linked with globally unstable modes and convectively unstable mechanisms, are discussed.

show abstract

“…Even though the importance of oblique fluctuations in initiating transition in attached high-speed boundary layers has received significant attention (Ma & Zhong 2005;Sivasubramanian & Fasel 2015;Hader & Fasel 2019), their role in separated high-speed flows has not been studied. Recent experiments (Benitez et al 2020) suggest that their amplification within the recirculation zone can trigger unsteadiness in transitional SBWLI flows. We utilize global resolvent and weakly nonlinear analyses to quantify amplification of unsteady upstream disturbances in a Mach 5 flow over a slender double wedge, and characterize their role in initiating transition to turbulence in high-speed separated boundary layers.…”

Section: Introductionmentioning

confidence: 99%

“…Even in the absence of global instability, high-speed separated flows are highly sensitive to upstream vortical disturbances (Dwivedi et al 2019), and small fluctuations around the laminar 2-D base flow can experience significant non-modal amplification that leads to the appearance of steady reattachment streaks (Dwivedi et al 2020b). Furthermore, recent experiments on the cone-flare configurations (Benitez et al 2020;Butler & Laurence 2021), which represent axisymmetric counterparts of slender double wedges, identify unsteady fluctuations in the separation zone. These fluctuations are significantly amplified in the recirculation zone and they play an important role in transition to turbulence (Butler & Laurence 2021).…”

Section: Introductionmentioning

confidence: 99%

Oblique transition in hypersonic double-wedge flow

Sidharth

Jovanović

2022

J. Fluid Mech.

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

Instability Measurements on an Axisymmetric Separation Bubble at Mach 6

Cited by 32 publications

References 16 publications

Interaction of second-mode disturbances with an incipiently separated compression-corner flow

Interaction of second-mode disturbances with an incipiently separated compression-corner flow

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

Oblique transition in hypersonic double-wedge flow

Contact Info

Product

Resources

About