Harmonic linearized Navier-Stokes equation on describing the effect of surface roughness on hypersonic boundary-layer transition

Zhao, Lijuan; Dong, Ming; Yang, Yanguang

doi:10.1063/1.5086912

Cited by 33 publications

(13 citation statements)

References 38 publications

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“…Computational and theoretical studies have also examined the influence of roughness on high-speed boundary-layer stability (Duan, Wang & Zhong 2010;Marxen et al 2010;Riley et al 2014;Groskopf & Kloker 2016;Zhao et al 2019;Dong & Zhao 2021;Haley & Zhong 2023). We first consider the impact of 2-D modifications of the surface.…”

Section: Effects Of Roughness On Transition To Turbulencementioning

confidence: 99%

“…However, placement near the trailing edge enhanced stability. Most recently, Zhao et al (2019) used the harmonic linearized Navier-Stokes equations to evaluate the effect of a 2-D hump or indentation on a flat wall on boundary-layer stability. They confirmed that the synchronization points of the instability waves are critical modulators of the impact of roughness.…”

Section: Effects Of Roughness On Transition To Turbulencementioning

confidence: 99%

“…Nonetheless, the potential thermal and mechanical benefits of a sustained laminar state in flight are such that roughness has previously been explored as an effective strategy to delay transition in high-speed boundary layers (Fujii 2006; Marxen, Iaccarino & Shaqfeh 2010; Riley, McNamara & Johnson 2014; Fong et al. 2015; Zhao, Dong & Yang 2019). In the present effort, we examine the influence of roughness location and shape on laminar-to-turbulence transition in a Mach 4.5 zero-pressure-gradient boundary layer using direct numerical simulation (DNS), and explain the observed shifts in transition location.…”

Section: Introductionmentioning

confidence: 99%

“…2014; Groskopf & Kloker 2016; Zhao et al. 2019; Dong & Zhao 2021; Haley & Zhong 2023). We first consider the impact of 2-D modifications of the surface.…”

Section: Introductionmentioning

confidence: 99%

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Optimal two-dimensional roughness for transition delay in high-speed boundary layer

Jahanbakhshi,

Zaki

2023

J. Fluid Mech.

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The influence of surface roughness on transition to turbulence in a Mach 4.5 boundary layer is studied using direct numerical simulations. Transition is initiated by the nonlinearly most dangerous inflow disturbance, which causes the earliest possible breakdown on a flat plate for the prescribed inflow energy and Mach number. This disturbance primarily comprises two normal second-mode instability waves and an oblique first mode. When localized roughness is introduced, its shape and location relative to the synchronization points of the inflow waves are confirmed to have a clear impact on the amplification of the second-mode instabilities. The change in modal amplification coincides with the change in the height of the near-wall region where the instability wave speed is supersonic relative to the mean flow; the net effect of a protruding roughness is destabilizing when placed upstream of the synchronization point and stabilizing when placed downstream. Assessment of the effect of the roughness location is followed by an optimization of the roughness height, abruptness and width with the objective of achieving maximum transition delay. The optimization is performed using an ensemble-variational (EnVar) approach, while the location of the roughness is fixed upstream of the synchronization points of the two second-mode waves. The optimal roughness disrupts the phase of the near-wall pressure waves, suppresses the amplification of the primary instability waves and mitigates the nonlinear interactions that lead to breakdown to turbulence. The outcome is a sustained non-turbulent flow throughout the computational domain.

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Section: Effects Of Roughness On Transition To Turbulencementioning

confidence: 99%

Section: Effects Of Roughness On Transition To Turbulencementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…2014; Groskopf & Kloker 2016; Zhao et al. 2019; Dong & Zhao 2021; Haley & Zhong 2023). We first consider the impact of 2-D modifications of the surface.…”

Section: Introductionmentioning

confidence: 99%

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Optimal two-dimensional roughness for transition delay in high-speed boundary layer

Jahanbakhshi,

Zaki

2023

J. Fluid Mech.

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“…where δ 99 = 8.7 denotes the nominal boundary-layer thickness at x = x 0 and J = 580. Such an allocation ensures that half of the total grid points are allocated to the boundary layer, which has also been used in our previous work (Zhao, Dong & Yang 2019;Song et al 2022).…”

Section: Nonlinear Evolution Of the Boundary-layer Perturbationsmentioning

confidence: 99%

Effect of cone rotation on the nonlinear evolution of Mack modes in supersonic boundary layers

Song,

Dong,

Zhao

2023

J. Fluid Mech.

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In this paper, we present a systematic study of the nonlinear evolution of the travelling Mack modes in a Mach 3 supersonic boundary layer over a rotating cone with a $7^{\circ }$ half-apex angle using the nonlinear parabolic stability equation (NPSE). To quantify the effect of cone rotation, six cases with different rotation rates are considered, and from the same streamwise position, a pair of oblique Mack modes with the same frequency but opposite circumferential wavenumbers are introduced as the initial perturbations for NPSE calculations. As the angular rotation rate $\varOmega$ increases such that $\bar \varOmega$ (defined as the ratio of the rotation speed of the cone to the streamwise velocity at the boundary-layer edge) varies from 0 to $O(1)$ , three distinguished nonlinear regimes appear, namely the oblique-mode breakdown, the generalised fundamental resonance and the centrifugal-instability-induced transition. For each regime, the mechanisms for the amplifications of the streak mode and the harmonic travelling waves are explained in detail, and the dominant role of the streak mode in triggering the breakdown of the laminar flow is particularly highlighted. Additionally, from the linear stability theory, the dominant travelling mode undergoes the greatest amplification for a moderate $\varOmega$ , which, according to the $e^N$ transition-prediction method, indicates premature transition to turbulence. However, this is in contrast to the NPSE results, in which a delay of the transition onset is observed for a moderate $\varOmega$ . Such a disagreement is attributed to the different nonlinear regimes appearing for different rotation rates. Therefore, the traditional transition-prediction method based on the linear instability should be carefully employed if multiple nonlinear regimes may appear.

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Stabilization of hypersonic boundary layer by combining micro-blowing and a porous coating

Liu,

Zhao,

Wen

et al. 2023

Acta Mech

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Harmonic linearized Navier-Stokes equation on describing the effect of surface roughness on hypersonic boundary-layer transition

Cited by 33 publications

References 38 publications

Optimal two-dimensional roughness for transition delay in high-speed boundary layer

Optimal two-dimensional roughness for transition delay in high-speed boundary layer

Effect of cone rotation on the nonlinear evolution of Mack modes in supersonic boundary layers

Stabilization of hypersonic boundary layer by combining micro-blowing and a porous coating

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