The effects of Mach and Reynolds number on the flow mixing properties of micro-ramp vortex generators in a supersonic boundary layer

Giepman, Rogier; Srivastava, Aabhas; Schrijer, F.F.J.; Oudheusden, B.W. van

doi:10.2514/6.2015-2779

Cited by 4 publications

(9 citation statements)

References 23 publications

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“…The flow field behind the Anderson micro ramps has been explored in great detail in the literature [9,16,18,25].…”

Section: Fig 1 Micro Ramp Geometrymentioning

confidence: 99%

“…Fig.17Stream-wise evolution of wake velocity with the present scaling, all configurations, including data from literature[12,25].…”

mentioning

confidence: 96%

“…The momentum addition near the wall is primarily governed by the stream-wise counter-rotating vortex pair (hereafter referred to as primary vortices), while the hairpin/ring like vortices only intermittently alter the effectiveness of the primary vortex pair [2,18]. The effects of Mach number, Reynolds number and device height on the various characteristics of the micro ramp wake have been addressed [12,25]. Various micro ramp configurations have also been tested to mitigate the shock induced separation [2].…”

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confidence: 99%

“…The effect of different micro ramp sizes, i.e. different device heights relative to the oncoming boundary layer thickness, on the wake properties has been investigated in the past [25,26]. These studies reported that the device height, regardless of the oncoming boundary layer thickness, can be used as the primary length scale while scaling the micro ramp wake properties.…”

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confidence: 99%

“…Fig. 16 Stream-wise evolution of wake velocity for (a) half-span angle sweep and (b) ramp angle sweep,including data from literature[12,25].…”

mentioning

confidence: 99%

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Relation Between Geometry and Wake Characteristics of a Supersonic Microramp

2021

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“…The flow field behind the Anderson micro ramps has been explored in great detail in the literature [9,16,18,25].…”

Section: Fig 1 Micro Ramp Geometrymentioning

confidence: 99%

“…Fig.17Stream-wise evolution of wake velocity with the present scaling, all configurations, including data from literature[12,25].…”

mentioning

confidence: 96%

mentioning

confidence: 99%

mentioning

confidence: 99%

“…Fig. 16 Stream-wise evolution of wake velocity for (a) half-span angle sweep and (b) ramp angle sweep,including data from literature[12,25].…”

mentioning

confidence: 99%

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Relation Between Geometry and Wake Characteristics of a Supersonic Microramp

2021

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Direct numerical simulation of supersonic boundary layers over a microramp: effect of the Reynolds number

Della Posta,

Blandino,

Modesti

et al. 2023

J. Fluid Mech.

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Microvortex generators are passive control devices smaller than the boundary layer thickness that energise the boundary layer to prevent flow separation with limited induced drag. In this work, we use direct numerical simulations (DNS) to investigate the effect of the Reynolds number in a supersonic turbulent boundary layer over a microramp vortex generator. Three friction Reynolds numbers are considered, up to $Re_\tau = 2000$ , for fixed free stream Mach number $M_\infty =2$ and fixed relative height of the ramp with respect to the boundary layer thickness. The high-fidelity data set sheds light on the instantaneous and highly three-dimensional organisation of both the wake and the shock waves induced by the microramp. The full access to the flow field provided by DNS allows us to develop a qualitative model of the near wake, explaining the internal convolution of the Kelvin–Helmholtz vortices around the low-momentum region behind the ramp. The overall analysis shows that numerical results agree excellently with recent experimental measurements in similar operating conditions and confirms that microramps effectively induce a significantly fuller boundary layer even far downstream of the ramp. Moreover, results highlight significant Reynolds number effects, which in general do not scale with the ramp height. Increasing Reynolds number leads to enhanced coherence of the typical vortical structures in the field, faster and stronger development of the momentum deficit region, increased upwash between the primary vortices from the sides of the ramp – and thus increased lift-up of the wake – and faster transfer of momentum towards the wall.

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High-fidelity simulations of microramp-controlled shock wave/boundary layer interaction

Della Posta,

Martelli,

Salvadore

et al. 2024

J. Fluid Mech.

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Microvortex generators (MVGs) are a promising solution to control shock wave/turbulent boundary layer interactions (SBLIs), especially in supersonic inlets. In this study, we examine the effects of a microramp vortex generator on an SBLI generated by an oblique shock wave and a turbulent boundary layer using direct numerical simulations (DNSs). Two cases, with and without the presence of a microramp, are compared in terms of their mean and unsteady flow features at free-stream Mach number equal to 2 and friction Reynolds number at the inviscid shock impingement equal to 600. The long integration period allows us to assess how microramps affect the typical low-frequency unsteadiness observed in SBLIs, and the data generated may serve as a reference for simulations of lower fidelity or reduced order models. The analysis shows that the three-dimensional microramp wake alters the interaction region dramatically, inducing a significant spanwise modulation and topology change of the separation. For example, tornado-like structures redistribute the flow in both the spanwise and wall-normal directions inside the recirculation region. The increase in momentum close to the wall by the ramp vortices effectively delays the onset of the separation and, thus, the separation length, but at the same time leads to a significant increase in the intensity of the wall-pressure fluctuations. We then characterise the mutual interaction between the arch-like vortices around the ramp wake and the SBLI. The specific spanwise vorticity shows that these vortices follow the edge of the separation and their intensity, apart from mean compressibility effects, is not affected by the shocks. The shocks, instead, are deformed in shape by the periodic impingement of the vortices, although the spectral analysis did not reveal any significant trace of their shedding frequency in the separation region. These Kelvin–Helmholtz vortices, however, may be relevant in the closure of the separation bubble. Fourier analysis also shows a constant increase, in both value and magnitude, in the low-frequency peak all along the span, suggesting that the motion of the separation shock remains coherent while being disturbed by the arch-like vortices and oscillating at a higher frequency in absolute terms.

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The effects of Mach and Reynolds number on the flow mixing properties of micro-ramp vortex generators in a supersonic boundary layer

Cited by 4 publications

References 23 publications

Relation Between Geometry and Wake Characteristics of a Supersonic Microramp

Relation Between Geometry and Wake Characteristics of a Supersonic Microramp

Direct numerical simulation of supersonic boundary layers over a microramp: effect of the Reynolds number

High-fidelity simulations of microramp-controlled shock wave/boundary layer interaction

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