Dilatational-wave-induced aerodynamic cooling in transitional hypersonic boundary layers

Zhu, Yiding; Gu, Dejian; Zhu, Wenkai; Chen, Shiyi; Lee, Cunbiao; Oran, Elaine S.

doi:10.1017/jfm.2020.1044

Cited by 21 publications

(11 citation statements)

References 50 publications

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“…The experiments were performed in the Mach 6 hypersonic wind tunnel at Peking University (Zhu et al 2018). The tunnel is a blow-down hypersonic facility, which can provide Mach 6 air flow through a relatively short axisymmetric nozzle, with a 160 mm exit diameter and open-jet test section.…”

Section: Experimental Apparatusmentioning

confidence: 99%

“…Second-mode instability is inviscid and behaves as acoustic waves reflecting between the solid wall and the sonic line in hypersonic boundary layers, and plays an increasingly important role as the Mach number increases (Fedorov 2011). Zhu et al (2018) identified that the second-mode instability is correlated with high-frequency fluid compression and expansion, and results in an additional heating peak before transition. This newly discovered mechanism of dilatational heating differs from the traditional theory that aerodynamic heating is due mainly to viscous dissipation, and has been described as a new principle for aerodynamic heating (Sun & Oran 2018).…”

Section: Introductionmentioning

confidence: 99%

“…This newly discovered mechanism of dilatational heating differs from the traditional theory that aerodynamic heating is due mainly to viscous dissipation, and has been described as a new principle for aerodynamic heating (Sun & Oran 2018). Based on the phase relationship between the pressure and the dilatation, a criterion of dilatational heating is proposed Lee & Jiang 2019;Zhu et al 2021).…”

Section: Introductionmentioning

confidence: 99%

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Instability evolution in the hypersonic boundary layer over a wavy wall

Zhu

Lee

et al. 2022

J. Fluid Mech.

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The effects of a wavy wall on the stability of a hypersonic boundary layer on a flared cone are investigated by detailed experimental measurements and direct numerical simulations. The non-contact optical measurement method of focused laser differential interferometry is used to measure the disturbance development within the wavy region. The measurement results show that the second mode for the wavy wall is suppressed significantly compared with the smooth wall, and that multiple disturbances at low frequencies appear within the wavy region. Numerical corroboration against experimental measurements reveals good quantitative agreement. It is found that the disturbances at $f=360$ kHz on the wavy wall are suppressed appreciably, which are very significant on the smooth wall. And the disturbances at $f=140$ kHz and $f=260$ kHz develop within the wavy region, and increase considerably. Also, the disturbances achieve a significant increase over the first half of a wavy trough and become more stable over the second half of a wavy trough. The physical mechanism is found to be due to the change in wall geometry and is attributed to the spatially modulated mean flow. The disturbance growth rate is closely related to the level of the mean-flow distortion.

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Section: Experimental Apparatusmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Instability evolution in the hypersonic boundary layer over a wavy wall

Zhu

Lee

et al. 2022

J. Fluid Mech.

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“…, respectively [28]. The admittance of the acoustic metasurface is a complex number and can be expressed as A = |A|e iθ , where |A| denotes the admittance magnitude and θ denotes the admittance phase.…”

Section: Fig 1 Schematic Illustration Of the Acoustic Metasurface With Subwavelength Groovesmentioning

confidence: 99%

“…More updated progresses could be found in Refs. [25][26][27][28]. Recently, Zhao et al [31] expanded the research subjects by introducing the acoustic metasurface concept.…”

Section: Introductionmentioning

confidence: 99%

Broadband Design of Acoustic Metasurfaces for the Stabilization of a Mach 4 Boundary Layer Flow

Zhao

Xiao

Wen

et al. 2021

Preprint

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A piecewise acoustic metasurface is designed to suppress the first mode while marginally amplifying the Mack second mode in a Mach 4 flat-plate boundary layer (BL) flow. The results of linear stability theory (LST) and the eN method demonstrate the stabilization effect and transition delay performance, respectively. However, the direct numerical simulation (DNS) results indicate that the designed broadband acoustic metasurface actually weakly excites the first mode with a slightly larger fluctuating pressure amplitude at the surface, which is in contrast to the analysis of LST. The discrepancies are found to lie in the ‘roughness’ effect caused by the recirculation zones inside the microslits and the alternating expansion and compression waves induced at the slit edges, which significantly amplifies the first mode. For further clarification of the competitive mechanism between the acoustic stabilization and ‘roughness’ destabilization effects of metasurfaces on the first mode, a carefully designed metasurface is installed at the maximum growth rate region, which excites the first mode on the metasurface but inhibits its development downstream.

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Generation of acoustic waves in the hypersonic boundary layer over a wavy wall

Zhu

et al. 2022

Sci. China Phys. Mech. Astron.

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Dilatational-wave-induced aerodynamic cooling in transitional hypersonic boundary layers

Abstract: Abstract

Cited by 21 publications

References 50 publications

Instability evolution in the hypersonic boundary layer over a wavy wall

Instability evolution in the hypersonic boundary layer over a wavy wall

Broadband Design of Acoustic Metasurfaces for the Stabilization of a Mach 4 Boundary Layer Flow

Generation of acoustic waves in the hypersonic boundary layer over a wavy wall

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