Understanding effects of nose-cone bluntness on hypersonic boundary layer transition using input-output analysis

Cook, David A.; Thome, John; Brock, Joseph M.; Nichols, Joseph W.; Candler, Graham V.

doi:10.2514/6.2018-0378

Cited by 24 publications

(4 citation statements)

References 13 publications

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“…Significant non-modal amplification of stationary disturbances initiated within the nose-tip vicinity is qualitatively consistent with the observation that transition is highly sensitive to wall roughness in the large-bluntness regime and originates near the nose tip [4]. Cook et al [25] examined the external stability of blunted cones with increasing nose radii and identified the unstable modes appearing in the entropy-layer that dominate second-mode boundarylayer instabilities. Amplification of planar and oblique traveling non-modal disturbances peaking in the entropy-layer has also been reported for blunt cones by Paredes et al [26].…”

Section: Introductionsupporting

confidence: 62%

Role of entropic-instabilities in laminar-turbulent transition on a blunted flat plate

Goparaju¹,

Gaitonde²

2021

Preprint

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The effects of entropic-instabilities on the laminar-turbulent transition dynamics of a blunted flat plate at Mach 4 are numerically investigated through linear and nonlinear approaches. Linear wavepacket analysis reveals amplifying oblique first-modes as well as planar and oblique entropylayer disturbances. The receptivity of entropic-instabilities is found to be largest for actuation seeded in the entropy-layer; the corresponding linear evolution is characterized by an intensification in the wall-normal plane, coupled with streamwise tilting. Disturbances in the entropy-layer interact non-linearly with each other through the oblique breakdown mechanism, inducing streamwise streaks in the boundary-layer. These undergo further destabilization downstream leading to turbulence onset. Different mechanisms of interest are extracted with modal decomposition techniques best suited for each. Dynamic mode decomposition (DMD) reveals sinuous subharmonic oscillations induced by the entropic-disturbances as the dominant streak instability mechanism. On the other hand, spectral proper orthogonal decomposition (SPOD) elicits the slanted hook -shaped structures in the temperature perturbations, which are attributable to the Orr like-mechanism in the entropy-layer. Furthermore, cross-bispectral mode decomposition (CBMD) shows that the temperature perturbations amplify on the crests of the low-speed streaks in the entropy-layer and generates disturbances through triadic interactions. These newer disturbances further interact, resulting in the transfer of perturbation energy into the boundary-layer. This eventually leads to spanwise homogenization and near-wall streak generation, reflecting late nonlinear stages of transition. Towards the end of breakdown region, spectral broadening accompanied by the appearance of an inertial sub-range in the boundary-layer indicates the approach of the flow towards turbulence.

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Section: Introductionsupporting

confidence: 62%

Role of entropic-instabilities in laminar-turbulent transition on a blunted flat plate

Goparaju¹,

Gaitonde²

2021

Preprint

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“…Computational analysis by Cook et al. (2018) and Paredes et al. (2019 c , d ) has shown significant non-modal growth of both planar and oblique travelling disturbances that peak within the entropy layer and above the boundary-layer edge.…”

Section: Introductionmentioning

confidence: 98%

Mechanism for frustum transition over blunt cones at hypersonic speeds

Paredes

Choudhari

2020

J. Fluid Mech.

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“…2018; Towne, Schmidt & Colonius 2018), subsonic aerofoils (Yeh & Taira 2019), turbulent Couette flows (Dawson & McKeon 2019) and hypersonic boundary layer transitions (Cook et al. 2018; Dwivedi et al. 2018).…”

Section: Introductionmentioning

confidence: 99%

“…For example, under the correct scaling of the wall-parallel wavenumbers, the self-similar hierarchies of response modes give rise to self-similar families of vortical structures. However, there has been less work applying this operator based decomposition to fully-developed compressible flows, with the exception of the recent studies on compressible jet flows (Jeun et al 2016;Towne et al 2018;Schmidt et al 2018), subsonic aerofoils (Yeh & Taira 2019), turbulent Couette flows (Dawson & McKeon 2019), and hypersonic boundary layer transitions (Cook et al 2018;Dwivedi et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Resolvent-based study of compressibility effects on supersonic turbulent boundary layers

2019

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The resolvent formulation of McKeon & Sharma (2010) is extended to the compressible Navier-Stokes equations. Resolvent analysis is applied to the supersonic turbulent boundary layer in order to study the validity of Morkovin's hypothesis, which postulates that high-speed turbulence structure in zero pressure-gradient turbulent boundary layers remains largely the same as its incompressible counterpart. Supersonic turbulent boundary layers with adiabatic wall boundary conditions at Mach numbers ranging from 2 to 4 are considered. Resolvent analysis highlights two distinct regions of the supersonic turbulent boundary layer in the wave parameter space: the relatively supersonic region and the relatively subsonic region. In the relatively supersonic region, where the flow is supersonic relative to the freestream, resolvent modes display structures consistent with Mach wave radiation that are absent in the incompressible regime. In the relatively subsonic region, we show that the low-rank approximation of the resolvent operator is an effective approximation of the full system and that the response modes predicted by the model exhibit universal and geometrically self-similar behaviour via a transformation given by the semi-local scaling. Moreover, with semi-local scaling, we show that the resolvent modes follow the same scaling law as their incompressible counterparts in this region, which has implications for modelling and the prediction of turbulent high-speed wall-bounded flows. We also show that the thermodynamic variables exhibit similar mode shapes to the streamwise velocity modes, supporting the strong Reynolds analogy. Finally, we demonstrate that the principal resolvent modes can be used to capture the energy distribution between momentum and thermodynamic fluctuations.

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Understanding effects of nose-cone bluntness on hypersonic boundary layer transition using input-output analysis

Cited by 24 publications

References 13 publications

Role of entropic-instabilities in laminar-turbulent transition on a blunted flat plate

Role of entropic-instabilities in laminar-turbulent transition on a blunted flat plate

Mechanism for frustum transition over blunt cones at hypersonic speeds

Resolvent-based study of compressibility effects on supersonic turbulent boundary layers

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