Effects of upstream boundary layer on the unsteadiness of shock-induced separation

Ganapathisubramani, Bharathram; Clemens, Noel T.; Dolling, D. S.

doi:10.1017/s0022112007006799

Cited by 295 publications

(194 citation statements)

References 39 publications

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“…The emergence of timeresolved particle image velocimetry (PIV) approaches made the above considerations possible. For example, Ganapathisubramani et al [18] have recently reported very long coherent structures of about fifty boundary-thicknesses long (termed "superstructures"), using PIV and Taylor's hypothesis (note that the use of Taylor's hypothesis may be valid as shown by Dennis and Nickels [8]). In their paper, one can find the scaling argument that the low frequency induced by the superstructure scales on U ∞ /2λ , where U ∞ is the upstream freestream velocity and λ the size of the superstructure.…”

Section: Introductionmentioning

confidence: 99%

Large-eddy simulation of low-frequency unsteadiness in a turbulent shock-induced separation bubble

Touber

Sandham

2009

Theor. Comput. Fluid Dyn.

447

245

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The need for better understanding of the low-frequency unsteadiness observed in shock wave/turbulent boundary layer interactions has been driving research in this area for several decades. We present here a large-eddy simulation investigation of the interaction between an impinging oblique shock and a Mach 2.3 turbulent boundary layer. Contrary to past large-eddy simulation investigations on shock/turbulent boundary layer interactions, we have used an inflow technique which does not introduce any energetically-significant low frequencies into the domain, hence avoiding possible interference with the shock/boundary layer interaction system. The large-eddy simulation has been run for much longer times than previous computational studies making a Fourier analysis of the low frequency possible. The broadband and energetic low-frequency component found in the interaction is in excellent agreement with the experimental findings. Furthermore, a linear stability analysis of the mean flow was performed and a stationary unstable global mode was found. The long-run large-eddy simulation data were analyzed and a phase change in the wall pressure fluctuations was found to coincide with the global-mode structure, leading to a possible driving mechanism for the observed low-frequency motions.Keywords shock boundary layer interaction · global mode · compressible turbulence · LES · low-frequency unsteadiness · separation bubble · digital filter · inflow turbulence PACS 47.40.Nm · 47.40.Ki · 47.27.ep

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Section: Introductionmentioning

confidence: 99%

Large-eddy simulation of low-frequency unsteadiness in a turbulent shock-induced separation bubble

Touber

Sandham

2009

Theor. Comput. Fluid Dyn.

447

245

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“…Ganapathisubramani, Clemens & Dolling 2007a, Humble et al 2009). The present characterization of the boundary layer may contribute to this topic by providing reference data for the undisturbed turbulent flow structure.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional vortex organization in a high-Reynolds-number supersonic turbulent boundary layer

et al. 2010

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Tomographic particle image velocimetry was used to quantitatively visualize the three-dimensional coherent structures in a supersonic (Mach 2) turbulent boundary layer in the region between y/δ = 0.15 and 0.89. The Reynolds number based on momentum thickness Re θ = 34 000. The instantaneous velocity fields give evidence of hairpin vortices aligned in the streamwise direction forming very long zones of lowspeed fluid, consistent with Tomkins & Adrian (J. Fluid Mech., vol. 490, 2003, p. 37). The observed hairpin structure is also a statistically relevant structure as is shown by the conditional average flow field associated to spanwise swirling motion. Spatial low-pass filtering of the velocity field reveals streamwise vortices and signatures of large-scale hairpins (height > 0.5δ), which are weaker than the smaller scale hairpins in the unfiltered velocity field. The large-scale hairpin structures in the instantaneous velocity fields are observed to be aligned in the streamwise direction and spanwise organized along diagonal lines. Additionally the autocorrelation function of the wallnormal swirling motion representing the large-scale hairpin structure returns positive correlation peaks in the streamwise direction (at 1.5δ distance from the DC peak) and along the 45 • diagonals, which also suggest a periodic arrangement in those directions. This is evidence for the existence of a spanwise-streamwise organization of the coherent structures in a fully turbulent boundary layer.

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“…There are two possible sources of the oscillation, upstream flow fluctuation or fluctuation propagating from the downstream of the shock wave. Ganapathisubramani et al [2,3] obtained a correlation between velocity fluctuation in the incoming flow and shock-foot motion; large-scale oscillation in the separation region had a low characteristic frequency, less than 1 kHz. Andreopoulos and Muck [4] argued that the turbulence of the incoming flow induced shock-wave oscillations.…”

Section: Introductionmentioning

confidence: 99%

Suppression of Low-Frequency Shock Oscillations over Boundary Layers by Repetitive Laser Pulse Energy Deposition

et al. 2016

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Abstract:The effect of repetitive energy deposition on low Strouhal number oscillations of the shock wave induced by boundary-layer interaction over a cylinder-flare model was studied. The fluctuation of the energy deposition frequency was induced in the flow, because the bubble generated by the energy deposition flowed downstream along the surface repeatedly. The region before the bubble size was affected by the energy deposition directly, so the fluctuation frequency was equal to the energy deposition frequency. However, the flare shock behavior at a position farther from the surface than the bubble size was also affected strongly by the energy deposition. For low-frequency unsteadiness and the effect of energy deposition on its unsteadiness, two categories have been observed. In the relatively small flare angle case, the flare shock was oscillated owing to the fluctuation induced by the boundary-layer interaction at the shock foot, and its oscillation occurred at 2.1 kHz with a small amplitude. The amplitude of this oscillation was decreased by highly repetitive energy depositions, and its amplitude could not be detected at a highly repetitive energy deposition. In the longer cylinder section case, the region of the shock-wave interaction was widened, and the amplitude of the flare shock oscillation was increased. In this case, the amplitude drastically decreased because of energy deposition.

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Effects of upstream boundary layer on the unsteadiness of shock-induced separation

Cited by 295 publications

References 39 publications

Large-eddy simulation of low-frequency unsteadiness in a turbulent shock-induced separation bubble

Large-eddy simulation of low-frequency unsteadiness in a turbulent shock-induced separation bubble

Three-dimensional vortex organization in a high-Reynolds-number supersonic turbulent boundary layer

Suppression of Low-Frequency Shock Oscillations over Boundary Layers by Repetitive Laser Pulse Energy Deposition

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