On shock-wave unsteadiness in separated flows

Subrahmanyam, D.; Kumar, Ghanendra; Sasidharan, Vaisakh

doi:10.1007/s12046-023-02177-1

Cited by 1 publication

(4 citation statements)

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“…2021; Duvvuri et al. 2023 and references therein). Early experimental studies of the flow clearly revealed unsteady and periodic flow phenomena (Maull 1960; Wood 1962; Kenworthy & Richards 1975; Kenworthy 1978).…”

Section: Introductionmentioning

confidence: 99%

“…For given flow Reynolds and Mach numbers, the state of flow unsteadiness is determined by Λ. See Duvvuri et al (2023) for a more detailed discussion on the unsteady flow states of pulsation and oscillation. show that even as flow moves into a higher dimensional geometric parameter space from the single-parameter spike-cylinder geometry, it only exhibits two distinct states of unsteadiness: pulsation and oscillation.…”

Section: Introductionmentioning

confidence: 99%

“…the separated boundary layer) that forms over the separation region/bubble is susceptible to flow instabilities, and growth of disturbances arising from such instabilities leads to interesting unsteady coupled dynamics of the overall flow system. These types of unsteady flows are distinct from SBLI and are classified as shock wave/separation region interaction (SSRI) problems (Duvvuri, Kumar & Sasidharan 2023).

Figure 1.Schematic illustrations of different flows with SBLI and SSRI.…”

Section: Introductionmentioning

confidence: 99%

“…See Duvvuri et al. (2023) for a more detailed discussion on the unsteady flow states of pulsation and oscillation.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A model for frequency scaling of flow oscillations in high-speed double cones

Kumar,

Sasidharan,

Kumara

et al. 2024

J. Fluid Mech.

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Coherent small-amplitude unsteadiness of the shock wave and the separation region over a canonical double cone flow, termed in literature as oscillation-type unsteadiness, is experimentally studied at Mach 6. The double cone model is defined by three non-dimensional geometric parameters: fore- and aft-cone angles ( $\theta _1$ and $\theta _2$ ), and ratio of the conical slant lengths ( $\varLambda$ ). Previous studies of oscillations have been qualitative in nature, and mostly restricted to a special case of the cone model with fixed $\theta _1 = 0^\circ$ and $\theta _2 = 90^\circ$ (referred to as the spike-cylinder model), where $\varLambda$ becomes the sole governing parameter. In the present effort we investigate the self-sustained flow oscillations in the $\theta _1$ - $\varLambda$ parameter space for fixed $\theta _2 = 90^\circ$ using high-speed schlieren visualisation. The experiments reveal two distinct subtypes of oscillations, characterised by the motion (or lack thereof) of the separation point on the fore-cone surface. The global time scale associated with flow oscillation is extracted using spectral proper orthogonal decomposition. The non-dimensional frequency (Strouhal number) of oscillation is seen to exhibit distinct scaling for the two oscillation subtypes. The relationship observed between the local flow properties, instability of the shear layer, and geometric constraints on the flow suggests that an aeroacoustic feedback mechanism sustains the oscillations. Based on this understanding, a simple model with no empiricism is developed for the Strouhal number. The model predictions are found to match well with experimental measurements. The model provides helpful physical insight into the nature of the self-sustained flow oscillations over a double cone at high speeds.

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