Transition scenario in hypersonic axisymmetrical compression ramp flow

Lugrin, Mathieu; Beneddine, Samir; Leclercq, Colin; Garnier, Éric; Bur, Reynald

doi:10.1017/jfm.2020.833

Cited by 34 publications

(51 citation statements)

References 62 publications

(163 reference statements)

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“…It can be observed that Δx + and Δz + are smaller than 10 except for the turbulent regions and the regions near the attachment line. The grid resolution is close to or even better than some other numerical simulations of boundary layer transition on 3-D configurations (Li et al 2008(Li et al , 2010Lugrin et al 2021). Table 2 presents the number of grid points per wavelength of the most amplified waves in various regions, showing that the spatial discretization is able to resolve all but the attachment-line instability.…”

Section: Discussionmentioning

confidence: 63%

“…Detailed grid resolution presented in Appendix A shows that the flow upstream of the late transition stage is fully resolved with respect to DNS standards, except for the attachment-line instabilities. When the flow becomes turbulent and the wall-shear stress is maximum, the boundary layer based on this mesh sizing becomes slightly under-resolved and the resolution is in between the typical LES and DNS resolutions (Garnier, Adams & Sagaut 2009;Lugrin et al 2021). Therefore, the computation corresponds to a quasi-direct numerical simulation (QDNS, such as defined by Spalart 2000).…”

Section: Numerical Simulationsmentioning

confidence: 99%

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Boundary layer transition and linear modal instabilities of hypersonic flow over a lifting body

Chen

Dong

et al. 2022

J. Fluid Mech.

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Boundary layer transition over a lifting body of 1.6 m length at $2^\circ$ angle of attack has been simulated at Mach 6 and a unit Reynolds number $1.0 \times 10^7$ m $^{-1}$ . The model geometry is the same as the Hypersonic Transition Research Vehicle designed by the China Aerodynamics Research and Development Center. Four distinct transitional regions are identified, i.e. windward vortex region, shoulder vortex region, windward cross-flow region and shoulder cross-flow region. Multi-dimensional linear stability analyses by solving the two-dimensional eigenvalue problem (spatial BiGlobal approach) and the plane-marching parabolized stability equations (PSE3D approach) are further carried out to uncover the dominant instabilities in the last three regions as well as the shoulder attachment-line region. The shoulder vortex is conducive to both inner and outer modes of shear-layer instability, of which the latter most likely trigger the vortex breakdown. A novel method is presented to substantially reduce the computational cost of BiGlobal and PSE3D in resolving the cross-flow instabilities in cross-flow regions. The peak frequencies of cross-flow modes lie between 15 and 45 kHz. Whereas oblique second Mack modes are marginally unstable in the windward cross-flow region, they could be strong enough to compete with the cross-flow modes in the shoulder cross-flow region. In the shoulder attachment-line region, there exists only one unstable mode of Mack instability, differing from previous studies that show a hierarchy of modes in the context of symmetrical attachment-line flows. Results of the numerical simulation and multi-dimensional stability analyses are compared when possible, showing a fair agreement between the two approaches and highlighting the necessity of considering non-parallel effects.

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Section: Discussionmentioning

confidence: 63%

Section: Numerical Simulationsmentioning

confidence: 99%

Boundary layer transition and linear modal instabilities of hypersonic flow over a lifting body

Chen

Dong

et al. 2022

J. Fluid Mech.

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“…Both SPOD and resolvent analyses have been extensively applied to flows such as wall-bounded flows (see Cossu, Pujals & Depardon 2009;Hellström & Smits 2014;Beneddine et al 2016;Tutkun & George 2017;Abreu et al 2020;Lugrin et al 2021), jets (Schmidt et al 2018;Lesshafft et al 2019) and airfoils (Symon, Sipp & McKeon 2019;Yeh & Taira 2019), to mention a few.…”

Section: Introductionmentioning

confidence: 99%

Identification and reconstruction of high-frequency fluctuations evolving on a low-frequency periodic limit cycle: application to turbulent cylinder flow

et al. 2022

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Oftentimes, turbulent flows exhibit a high-frequency turbulent component developing on a strong low-frequency periodic motion. In such cases, the low-frequency motion may strongly influence the spatio-temporal features of the high-frequency component. A typical example of such behaviour is the flow around bluff bodies, for which the high-frequency turbulent component, characterized by Kelvin–Helmholtz structures associated with thin shear layers, depends on the phase of the low-frequency vortex-shedding motion. In this paper, we propose extended versions of spectral proper orthogonal decomposition (SPOD) and of resolvent analysis that respectively extract and reconstruct the high-frequency turbulent fluctuation field as a function of the phase of the low-frequency periodic motion. These approaches are based on a quasi-steady (QS) assumption, which may be justified by the supposedly large separation between the frequencies of the periodic and turbulent components. After discussing their relationship to more classical Floquet-like analyses, the new tools are illustrated on a simple periodically varying linear Ginzburg–Landau model, mimicking the overall characteristics of a turbulent bluff-body flow. In this simple model, we in particular assess the validity of the QS approximation. Then, we consider the case of turbulent flow around a squared-section cylinder at a Reynolds number of $Re=22\,000$ , for which we show reasonable agreement between the extracted spatio-temporal fluctuation field and the prediction of QS resolvent analysis at the various phases of the periodic vortex-shedding motion.

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“…They therefore pointed out that it is necessary to distinguish the streamwise streaks from the convective instability waves in order to explore the transition nature. Recently, Lugrin et al (2021b) investigated the experiments of Benay et al (2006) using a high-fidelity simulation and revealed several possible transition paths via perturbing the incoming flow with a white noise. However, their study only focused on the convective instabilities and ignored the intrinsic instability.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, Lugrin et al. (2021 b ) investigated the experiments of Benay et al. (2006) using a high-fidelity simulation and revealed several possible transition paths via perturbing the incoming flow with a white noise.…”

Section: Introductionmentioning

confidence: 99%

Transition to turbulence in hypersonic flow over a compression ramp due to intrinsic instability

et al. 2022

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In this work, a transition process in a hypersonic flow over a cold-wall compression ramp is studied using direct numerical simulation (DNS) and global stability analysis (GSA). The free-stream Mach number and the Reynolds number based on the flat-plate length are 7.7 and $8.6 \times 10^5$ , respectively. The shock-induced pressure rise causes the boundary layer to separate on the flat plate, forming a separation bubble around the corner. Without introducing any external disturbances, the DNS captures the transition to turbulence downstream of flow reattachment. The DNS results agree well with the experimental data as well as theoretical predictions. To uncover the intrinsic instability in the flow system, GSA is employed to investigate the three-dimensionality of the two-dimensional base flow. Several stationary and oscillatory unstable modes are revealed, which result in spanwise periodicity inside and downstream of the separation bubble. The GSA and DNS results indicate that the intrinsic instability of the flow system triggers the formation of streamwise counter-rotating vortices and boundary-layer streaks near reattachment. The downstream transition to turbulence starts from the breakdown of the streamwise vortices and streaks. Moreover, the second harmonic of the most unstable global mode and a broadband low-frequency unsteadiness occur in the saturated flow, which has a significant influence on the transition process. In summary, the present study demonstrates a transition process in a hypersonic compression-ramp flow as a result of the intrinsic instability of the flow system.

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Transition scenario in hypersonic axisymmetrical compression ramp flow

Abstract: Abstract

Cited by 34 publications

References 62 publications

Boundary layer transition and linear modal instabilities of hypersonic flow over a lifting body

Boundary layer transition and linear modal instabilities of hypersonic flow over a lifting body

Identification and reconstruction of high-frequency fluctuations evolving on a low-frequency periodic limit cycle: application to turbulent cylinder flow

Transition to turbulence in hypersonic flow over a compression ramp due to intrinsic instability

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