Receptivity of Hypersonic Boundary Layers to Acoustic and Vortical Disturbances (Invited)

Balakumar, Ponnampalam

doi:10.2514/6.2015-2473

Cited by 23 publications

(10 citation statements)

References 58 publications

(78 reference statements)

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“…The respective gains are summarized in table 2. Firstly, the slow acoustic waves yielded a gain ≈1.9 times greater than that of the fast acoustic waves, which corroborates the general understanding that slow waves dominate acoustically induced transition onset in adiabatic-wall high-speed boundary layers (MZ3; Balakumar 2015). Vortical waves yielded a gain nearly identical to G c all , suggesting that transient streamwise jets excited by vortical disturbances is the dominant receptivity mechanism for the current configuration.…”

Section: Optimal Global Receptivity Analysissupporting

confidence: 77%

Global receptivity analysis: physically realizable input–output analysis

2023

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In the context of transition analysis, linear input–output analysis determines the worst-case disturbances to a laminar base flow based on a generic right-hand-side volumetric/boundary forcing term. The worst-case forcing is not physically realizable, and, to our knowledge, a generic framework for posing physically realizable worst-case disturbance problems is lacking. In natural receptivity analysis, disturbances are forced by matching (typically local) solutions within the boundary layer to outer solutions consisting of free-stream vortical, entropic and acoustic disturbances. We pose a scattering formalism to restrict the input forcing to a set of realizable disturbances associated with plane-wave solutions of the outer problem. The formulation is validated by comparing with direct numerical simulations of a Mach 4.5 flat-plate boundary layer. We show that the method provides insight into transition mechanisms by identifying those linear combinations of plane-wave disturbances that maximize energy amplification over a range of frequencies. We also discuss how the framework can be extended to accommodate scattering from shocks and in shock layers for supersonic flow.

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Section: Optimal Global Receptivity Analysissupporting

confidence: 77%

Global receptivity analysis: physically realizable input–output analysis

2023

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“…20 show the results for the sharp cone Cases 1, 2, and 3 and Figs.21 and 24show the results for the blunt cone Cases 4 and 5.…”

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confidence: 88%

“…The receptivity process in hypersonic flows has been investigated for flow over flat plates, wedges, and cones at different flow conditions. 20 It was found that amplitudes of the instability waves generated by the slow acoustic freestream disturbances are about 3-5 times the amplitude of the freestream disturbances. The next part of the problem is to determine criteria that can be used to estimate the transition onset point.…”

Section: Secondary Instability and Breakdown To Turbulencementioning

confidence: 99%

Transition Prediction in Hypersonic Boundary Layers Using Receptivity and Freestream Spectra

Balakumar

Chou

2018

AIAA Journal

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Boundary-layer transition in hypersonic flows over a straight cone can be predicted using measured freestream spectra, receptivity, and threshold values for the wall pressure fluctuations at the transition onset points. Simulations are performed for hypersonic boundary-layer flows over a 7-degree half-angle straight cone with varying bluntness at a freestream Mach number of 10. The steady and the unsteady flow fields are obtained by solving the two-dimensional Navier-Stokes equations in axisymmetric coordinates using a 5 th -order accurate weighted essentially non-oscillatory (WENO) scheme for space discretization and using a third-order total-variation-diminishing (TVD) Runge-Kutta scheme for time integration. The calculated N-factors at the transition onset location increase gradually with increasing unit Reynolds numbers for flow over a sharp cone and remain almost the same for flow over a blunt cone. The receptivity coefficient increases slightly with increasing unit Reynolds numbers. They are on the order of 4 for a sharp cone and are on the order of 1 for a blunt cone. The location of transition onset predicted from the simulation including the freestream spectrum, receptivity, and the linear and the weakly nonlinear evolutions yields a solution close to the measured onset location for the sharp cone. The simulations over-predict transition onset by about twenty percent for the blunt cone.

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“…For flows over flat plates and sharp cones, this work has been extended to predict that slow acoustic waves in the free-stream, outside of the shock, are the most important waves for activation of the Mack mode. However, free-stream vortical waves also play a role, and can also activate modal boundary layer growth [14][15][16]. Recent experiments involving schlieren imaging of Mach 6 flow over ogive-cylinder geometries revealed the presence of low-frequency instabilities in addition to the highfrequency Mack 2 nd mode [17].…”

Section: Introductionmentioning

confidence: 99%

Free-stream receptivity of a hypersonic blunt cone using input–output analysis and a shock-kinematic boundary condition

Cook

Nichols

2022

Theor. Comput. Fluid Dyn.

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Understanding the receptivity of hypersonic flows to free-stream disturbances is crucial for predicting laminar to turbulent boundary layer transition. Input-output analysis as a receptivity tool considers which free-stream disturbances lead to the largest response from the boundary layer using the global linear dynamics. Two technical challenges are addressed. First, we extend recent work by Kamal et al. [1] and restrict the allowable forcing to physically realizable inputs via a free-stream boundary modification to the classic input-output formulation. Second, we develop a hierarchical input-output (H-IO) analysis which allows us to solve the three-dimensional problem at a fraction of the computational cost otherwise associated with directly inverting the fully three-dimensional resolvent operator. Next, we consider Mach 5.8 flows over a sharp cone and blunt cone with a 3.6 mm spherically blunt tip. H-IO correctly predicts that the sharp cone boundary layer is most receptive to slow acoustic waves at an optimal incidence angle of 10 • , validating the method. We then investigate the effect of free-stream disturbances on the blunt cone boundary layer, and identify two distinct vorticity-dominated receptivity mechanisms for the oblique first mode instability at 10 kHz and an entropy layer instability at 75 kHz. Our results reveal these receptivity processes to be highly three-dimensional in nature, involving both the nose-tip and excitation along narrow bands at certain azimuthal angles along the oblique shock downstream. We interpret these processes in terms of critical angles from linear shock/perturbation interaction theory.

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Receptivity of Hypersonic Boundary Layers to Acoustic and Vortical Disturbances (Invited)

Cited by 23 publications

References 58 publications

Global receptivity analysis: physically realizable input–output analysis

Global receptivity analysis: physically realizable input–output analysis

Transition Prediction in Hypersonic Boundary Layers Using Receptivity and Freestream Spectra

Free-stream receptivity of a hypersonic blunt cone using input–output analysis and a shock-kinematic boundary condition

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