Steady longitudinal vortices in supersonic turbulent separated flows

Schülein, Erich; Trofimov, V. M.

doi:10.1017/s0022112010006105

Cited by 21 publications

(24 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…figures 5, 6, 11, and 12, the spanwise length scale of these regions is approximately δ, which is in agreement with the value reported in Loginov et al (2006). The spanwise wavelength of a pair of momentum perturbation regions is thus 2δ, and this value agrees with the natural spanwise wavelength of streamwise vortex pairs in STBLI flows, which was determined by Schülein & Trofimov (2011). Using small vortex generators, they artificially introduced disturbances upstream of compression-ramp STBLIs and studied the properties of the streamwise vortices formed in the interaction.…”

Section: Discussionsupporting

confidence: 86%

“…at conditions that are almost identical to those investigated here, the natural spanwise wavelength is close to 2δ. Schülein & Trofimov (2011) found this value to be insensitive to the Reynolds number and to depend on downstream properties such as the ramp angle and interaction strength.…”

Section: Discussionmentioning

confidence: 98%

“…In STBLI flows, these structures are most commonly observed using surface oil flow visualizations (e.g. Settles, Fitzpatrick & Bogdonoff 1979;Smits & Dussauge 2006;Schülein & Trofimov 2011), and they have also been observed in the time-averaged flow obtained from LES (Loginov et al 2006).…”

mentioning

confidence: 92%

“…As suggested by Loginov et al (2006) and Schülein & Trofimov (2011), the structures are expected to display some degree of unsteadiness in a turbulent shock/boundary layer interaction, especially if steady disturbances in the upstream boundary layer, which tend to pin the structures to preferred spanwise locations, are absent or insignificant. In this paper, we present evidence for unsteady Görtler-type vortices in a Mach 3 compression-ramp STBLI.…”

mentioning

confidence: 95%

See 3 more Smart Citations

Low-frequency dynamics in a shock-induced separated flow

et al. 2016

View full text Add to dashboard Cite

The low-frequency unsteadiness in the direct numerical simulation of a Mach 2.9 shock wave/turbulent boundary layer interaction with mean flow separation is analysed using dynamic mode decomposition (DMD). The analysis is applied both to threedimensional and spanwise-averaged snapshots of the flow. The observed low-frequency DMD modes all share a common structure, characterized by perturbations along the shock, together with streamwise-elongated regions of low and high momentum that originate at the shock foot and extend into the downstream flow. A linear superposition of these modes, with dynamics governed by their corresponding DMD eigenvalues, accurately captures the unsteadiness of the shock. In addition, DMD analysis shows that the downstream regions of low and high momentum are unsteady and that their unsteadiness is linked to the unsteadiness of the shock. The observed flow structures in the downstream flow are reminiscent of Görtler-like vortices that are present in this type of flow due to an underlying centrifugal instability, suggesting a possible physical mechanism for the low-frequency unsteadiness in shock wave/turbulent boundary layer interactions.

show abstract

Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 98%

mentioning

confidence: 92%

mentioning

confidence: 95%

See 2 more Smart Citations

Low-frequency dynamics in a shock-induced separated flow

et al. 2016

View full text Add to dashboard Cite

show abstract

“…Another aspect is their short integration time, which might not capture lowfrequency modulations of such flow structures. In accordance with experimental observations (Görtler 1941;Floryan 1991;Schülein & Trofimov 2011) as well as numerical findings (Loginov et al 2006;Grilli et al 2013), the spanwise width of each vortex pair is approximately 2 δ 0 . The spanwise width of our computational domain of L z = 4.5 δ 0 in combination with periodic boundary conditions allows flow structures with a spanwise wavelength of at most 4.5 δ 0 to be captured.…”

Section: Instantaneous and Mean Flow Organisationsupporting

confidence: 89%

Unsteady effects of strong shock-wave/boundary-layer interaction at high Reynolds number

2017

View full text Add to dashboard Cite

We analyse the low-frequency dynamics of a high-Reynolds-number impinging shockwave/turbulent boundary-layer interaction (SWBLI) with strong mean-flow separation. The flow configuration for our grid-converged large-eddy simulations (LES) reproduces recent experiments for the interaction of a Mach 3 turbulent boundary layer with an impinging shock that nominally deflects the incoming flow by 19.6○ . The Reynolds number based on the incoming boundary layer thickness of Re δ0 ≈ 203 ⋅ 10 3 is considerably higher than in previous LES studies. The very long integration time of 3805 δ 0 U 0 allows for an accurate analysis of low-frequency unsteady effects. Experimental wallpressure measurements are in good agreement with the LES data. Both datasets exhibit the distinct plateau within the separated-flow region of a strong SWBLI. The filtered three-dimensional flow field shows clear evidence of counter-rotating streamwise vortices originating in the proximity of the bubble apex. Contrary to previous numerical results on compression ramp configurations, these Görtler-like vortices are not fixed at a specific spanwise position, but rather undergo a slow motion coupled to the separationbubble dynamics. Consistent with experimental data, power spectral densities (PSD) of wall-pressure probes exhibit a broadband and very energetic low-frequency component associated with the separation-shock unsteadiness. Sparsity-promoting dynamic mode decompositions (SPDMD) for both spanwise-averaged data and wall-plane snapshots yield a classical and well-known low-frequency breathing mode of the separation bubble, as well as a medium-frequency shedding mode responsible for reflected and reattachment shock corrugation. SPDMD of the two-dimensional skin-friction coefficient further identify streamwise streaks at low frequencies that cause large-scale flapping of the reattachment line. The PSD and SPDMD results of our impinging SWBLI support the theory that an intrinsic mechanism of the interaction zone is responsible for the lowfrequency unsteadiness, in which Görtler-like vortices might be seen as a continuous (coherent) forcing for strong SWBLI.

show abstract