Three-dimensionality of hypersonic laminar flow over a double cone

Hao, Jiaao; Fan, Jianhui; Wen, Chih-Yung

doi:10.1017/jfm.2021.1137

Cited by 26 publications

(34 citation statements)

References 56 publications

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“…Both stationary and oscillatory global modes were revealed using GSA (see, e.g. Nichols et al 2017;Sidharth et al 2018;Hao et al 2022). The formation of streamwise streaks and low-frequency unsteadiness in such flows are closely linked to the intrinsic instability.…”

Section: Discussionmentioning

confidence: 99%

“…It is interesting to note that self-excited instability is ubiquitous in separated flows involving SWBLI. Examples are compression-ramp flow (Egorov, Neiland & Shredchenko 2011;Sidharth et al 2017), shock impingement on a flat plate (Robinet 2007;Nichols et al 2017), double-wedge flow (Sidharth et al 2018), double-cone flow (Hao et al 2022) and flow over a hollow cylinder/flare (Brown et al 2009;Lugrin et al 2021a). Both stationary and oscillatory global modes were revealed using GSA (see, e.g.…”

Section: Discussionmentioning

confidence: 99%

“…2018), double-cone flow (Hao et al. 2022) and flow over a hollow cylinder/flare (Brown et al. 2009; Lugrin et al.…”

Section: Discussionmentioning

confidence: 99%

“…2018; Hao et al. 2022). The formation of streamwise streaks and low-frequency unsteadiness in such flows are closely linked to the intrinsic instability.…”

Section: Discussionmentioning

confidence: 99%

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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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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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

et al. 2022

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“…double-cone flow (Hao et al. 2022), shock impingement on a flat plate (Robinet 2007; Hildebrand et al. 2018) and flow over a hollow cylinder/flare (Brown et al.…”

Section: Introductionmentioning

confidence: 99%

Stability of hypersonic flow over a curved compression ramp

Hao¹,

Guo²,

Wen³

et al. 2023

J. Fluid Mech.

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In this work, the stability of hypersonic flow over a curved compression ramp is studied using several stability analysis tools and direct numerical simulations (DNS). The free-stream Mach number and the unit Reynolds number are 7.7 and $4.2 \times 10^6$ m $^{-1}$ , respectively. Corner rounding is considered to alter the separation bubble flow so as to suppress the intrinsic instability of the compression-ramp flow. The variation of intrinsic instability is confirmed by global stability analysis. Subsequently, resolvent analysis is employed to examine the response of intrinsically stable flows to external disturbances. It is shown that the considered flows strongly amplify low-frequency streamwise streaks with a preferential spanwise wavelength. This result is verified using DNS by introducing a random forcing upstream of the separation point. Furthermore, both resolvent analysis and DNS demonstrate that the separation bubble contributes little to the selection of the spanwise wavelength of streamwise streaks. The combined effects of convective and intrinsic instabilities are also explored using DNS. A better agreement with experimental data is achieved after introducing upstream disturbances in an inherently unstable flow.

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