Role of Boundary-Layer on Unsteadiness on a Mach 2 Swept-Ramp Shock/Boundary-Layer Interaction Using 50 kHz PIV

Vanstone, Leon; Saleem, Mohammad; Seckin, Serdar; Clemens, Noel T.

doi:10.2514/6.2017-0757

Cited by 15 publications

(4 citation statements)

References 19 publications

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“…In this respect we note that the two key elements which we have identified as being responsible for the observed low-frequency unsteadiness, namely spanwise undulation of the separation line and convection of pressure disturbances, have been observed previously in several studies of swept SBLIs. In fact, the presence of ripples in the instantaneous separation line was first pinpointed in the studies of Vanstone et al (2017) and Vanstone & Clemens (2019). They found that these structures move at approximately 70-80 % of the cross-stream velocity, hence well in line with the present study.…”

Section: Discussionsupporting

confidence: 89%

“…Depending on the shock strength and the sweep angle, the interaction is characterized by either parallel or diverging separation/reattachment lines along the spanwise direction, which correspond to cylindrical or conical symmetry conditions, respectively (Settles, Perkins & Bogdonoff 1980). This is the case for flows over swept compression ramps (Settles et al 1980;Erengil & Dolling 1993;Vanstone et al 2017;Adler & Gaitonde 2018, 2020, around sharp fins (Schmisseur & Dolling 1994;Gaitonde et al 1999;Arora, Mears & Alvi 2019) and for swept impinging oblique SBLIs (Doehrmann et al 2018;Padmanabhan et al 2021). All the above studies of swept SBLIs agree about the importance of three-dimensional effects on low-frequency unsteadiness, with consensus on an increase of the typical frequencies with the sweep angle.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On low-frequency unsteadiness in swept shock wave–boundary layer interactions

et al. 2023

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We derive a scaling law for the characteristic frequencies of wall pressure fluctuations in swept shock wave/turbulent boundary layer interactions in the presence of cylindrical symmetry, based on analysis of a direct numerical simulations database. Direct numerical simulations in large domains show evidence of spanwise rippling of the separation line, with typical wavelength proportional to separation bubble size. Pressure disturbances around the separation line are shown to be convected at a phase speed proportional to the cross-flow velocity. This information is leveraged to derive a simple model for low-frequency unsteadiness, which extends previous two-dimensional models (Piponniau et al., J. Fluid Mech., vol. 629, 2009, pp. 87–108), and which correctly predicts growth of the typical frequency with the sweep angle. Inferences regarding the typical frequencies in more general swept shock wave/turbulent boundary layer interactions are also discussed.

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Section: Discussionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

On low-frequency unsteadiness in swept shock wave–boundary layer interactions

et al. 2023

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“…In addition, pulseburst PIV data have been acquired in the Multiphase Shock Tube to study the transient onset of a von Kármán vortex street shed from a cylinder [18] and particle drag in a shocked dense gas-solid flow [19]. Pulse-burst PIV has seen an extension to longer acquisition periods by Miller et al [20] and supersonic application by Vanstone et al [21] and Beresh et al [22]. In all these cases, temporal phenomena were measured by the high repetition rates of pulse-burst PIV and are key to understanding the dominant physics describing the behavior of each of these flows.…”

Section: Introductionmentioning

confidence: 99%

‘Postage-stamp PIV’: small velocity fields at 400 kHz for turbulence spectra measurements

Beresh

Henfling

Spillers

et al. 2018

Meas. Sci. Technol.

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Time-resolved particle image velocimetry recently has been demonstrated in high-speed flows using a pulse-burst laser at repetition rates reaching 50 kHz. Turbulent behavior can be measured at still higher frequencies if the field of view is greatly reduced and lower laser pulse energy is accepted. Current technology allows image acquisition at 400 kHz for sequences exceeding 4000 frames but for an array of only 128 × 120 pixels, giving the moniker of ‘postage-stamp PIV’. The technique has been tested far downstream of a supersonic jet exhausting into a transonic crossflow. Two-component measurements appear valid until 120 kHz, at which point a noise floor emerges whose magnitude is dependent on the reduction of peak locking. Stereoscopic measurement offers three-component data for turbulent kinetic energy spectra, but exhibits a reduced signal bandwidth and higher noise in the out-of-plane component due to the oblique camera images. The resulting spectra reveal two regions exhibiting power-law dependence describing the turbulent decay. The frequency response of the present measurement configuration exceeds nearly all previous velocimetry measurements in high speed flow.

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“…In this respect, we note that in spanwise homogeneous SBLIs, typical low-frequency oscillations arising around the separation point have a typical frequency St L ≈ 0.03, hence two orders of magnitude less than the dominant frequencies in the boundary layer. Experiments and numerical studies of SBLIs in the presence of flow skewing, including compression ramps (Erengil & Dolling 1993;Vanstone et al 2017;Adler & Gaitonde 2018, sharp fins (Schmisseur & Dolling 1994;Gaitonde et al 1999 Figure 15 shows evidence for 2-D-like dynamics in the proximity of the separation and reattachment points, as well as in the secondary APG region. This is the likely consequence that the dynamics in the symmetry plane is similar to nominally 2-D interactions.…”

Section: Frequency Spectramentioning

confidence: 99%

On wall pressure fluctuations in conical shock wave/turbulent boundary layer interaction

2023

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The structure and the frequency spectra of wall pressure fluctuations beneath a planar turbulent boundary layer interacting with a conical shock wave at Mach number $M_\infty =2.05$ and Reynolds number $\textit {Re}_\theta \approx 630$ (based on the upstream boundary layer momentum thickness) are examined to elucidate the effects of pressure gradient and flow separation on the characteristics of the wall pressure fluctuations, by exploiting a direct numerical simulation database. Upstream of the interaction, in the zero pressure gradient region, wall pressure statistics compare well with canonical compressible boundary layers in terms of fluctuation intensities and frequency spectra. Across the main interaction zone (APG1), the root-mean-square of wall pressure fluctuations becomes very large (corresponding to approximately 173.3 dB), with maximum increase approximately 12.7 dB from the incoming level. In the second adverse pressure gradient zone (APG2), the root-mean-square of wall pressure fluctuations attains a second peak (corresponding to $164.7$ dB), with an increase of 8.4 dB from the upstream level. Both the APG1 and APG2 regions feature a substantial fraction of flow reversal events, which are, however, scattered and interspersed with regions of attached flow. The wall pressure power spectral density exhibits a broadband and energetic low-frequency component associated with the global unsteadiness of the separation bubble/conical shock system. Analysis of the two-point correlations and wavenumber/frequency spectra of wall pressure fluctuations further suggests that the typical eddies become more elongated along the spanwise direction, as the flow in the separated region tends to escape the centreline, and the convection velocity is significantly reduced.

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Role of Boundary-Layer on Unsteadiness on a Mach 2 Swept-Ramp Shock/Boundary-Layer Interaction Using 50 kHz PIV

Cited by 15 publications

References 19 publications

On low-frequency unsteadiness in swept shock wave–boundary layer interactions

On low-frequency unsteadiness in swept shock wave–boundary layer interactions

‘Postage-stamp PIV’: small velocity fields at 400 kHz for turbulence spectra measurements

On wall pressure fluctuations in conical shock wave/turbulent boundary layer interaction

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