Salient and smooth edge ramps inducing turbulent boundary layer separation: Flow characterization for control perspective

Debien, Antoine; Aubrun, Sandrine; Mazellier, Nicolas; Kourta, Azeddine

doi:10.1016/j.crme.2014.05.003

Cited by 8 publications

(5 citation statements)

References 16 publications

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“…as much as a 75 % reduction of its baseline value) for St A,min ≈ 0.25 to 0.35. St A,min corresponds to St L = St A L * R ≈ 0.45 to 0.55, which matches relatively well the natural shedding frequency of the separated shear layer, estimated at St L ≈ 0.53 to 0.66 by Debien et al [6]. For St A > St A,min , L * R increases once again, recovering its baseline value for St A ≈ 1.…”

Section: Flow Forcing and Its Effects On Scalingsupporting

confidence: 88%

“…Over the first half of the recirculation region, the separated shear layer seems to behave almost as a free shear layer [3]. Similarities include the value of its growth rate [4,5] as well as the presence of a convective instability ( [6,7], among others) reminding the convection of large-scale structures reported by Brown and Roshko [8] in free shear layers. Downstream of the reattachment point, the flow slowly relaxes to a new boundary layer [9].…”

Section: Introductionsupporting

confidence: 60%

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Mass entrainment-based model for separating flows

et al. 2018

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Recent studies have shown that entrainment effectively describes the behaviour of natural and forced separating/reattaching flows developing behind bluff bodies, potentially paving the way to new, scalable separation control strategies. In this perspective, we propose a new interpretative framework for separated flows, based on mass entrainment. The cornerstone of the approach is an original model of the mean flow, representing it as a stationary vortex scaling with the mean recirculation length. We test our model on a set of mean separated topologies, obtained by forcing the flow over a descending ramp with a rack of synthetic jets. Our results show that both the circulation of the vortex and its characteristic size scale simply with the intensity of the backflow (i.e. the amount of mass going through the recirculation region). This suggests that the vortex model captures the essential functioning of mean mass entrainment, and that it could be used to model and/or predict the mean properties of separated flows. In addition, we use the vortex model to show that the backflow (i.e. an integral quantity) can be estimated from a single wall-pressure measurement (i.e. a pointwise quantity). Since the backflow also appears to be anticorrelated to the characteristic velocity of the synthetic jets, this finding suggests that industrially deployable, closed-loop control systems based on mass entrainment might be within reach.

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Section: Flow Forcing and Its Effects On Scalingsupporting

confidence: 88%

Section: Introductionsupporting

confidence: 60%

Mass entrainment-based model for separating flows

et al. 2018

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“…In the case of the ramp with a sufficient inclination angle, the adverse pressure gradient generated promotes the flow separation. The location of the separation depends on the nature of the edge (Thacker et al 2012;Debien et al 2014). In the case of a model with a salient edge, the separation point is fixed at the ramp edge.…”

Section: Introductionmentioning

confidence: 99%

Analysis and characterization of ramp flow separation

2015

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“…Of the geometries used, most fall in the range of L/W ∼ 1 (L/W = 0.98 in the current study). Exceptions were the studies by Debien et al (2014) and Lin (1992), whose values of L/W = 0.24 and 0.176, respectively, were due to a uniquely wide, 2 m, test section and a comparatively small ramp length, respectively. It is interesting to note that these two studies did not mention three-dimensional effects and the flows were treated in terms of two-dimensional terminology.…”

Section: Flow Separation Topographymentioning

confidence: 92%

Experimental characterization of smooth body flow separation topography and topology on a two-dimensional geometry of finite span

et al. 2022

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A smooth body, adverse pressure gradient (APG), turbulent boundary layer (TBL) separation is experimentally studied. The geometry features canonical TBL development prior to encountering a smooth, two-dimensional convex ramp geometry of finite span onto which a streamwise APG that is fully adjustable is imposed. Both large- and small-scale separations are studied, and all data are archived on the NASA Turbulence Modeling Resource website. This paper describes the large-scale separation case with focus on the surface topography and topology of both separation and reattachment. Despite the spanwise uniform approach TBL and ramp geometry, the separation is highly three-dimensional but the reattachment is spanwise uniform. The surface flow topology is characterized by the ‘owl-face pattern of the fourth kind’ – found to be highly repeatable over multiple experiments. This ubiquitous topology has been reported for a variety of flows including inclined bodies of revolution. It is demonstrated that the APG and the secondary flow associated with the sidewall–ramp juncture is responsible for the formation of the surface separation patterns.

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Salient and smooth edge ramps inducing turbulent boundary layer separation: Flow characterization for control perspective

Cited by 8 publications

References 16 publications

Mass entrainment-based model for separating flows

Mass entrainment-based model for separating flows

Analysis and characterization of ramp flow separation

Experimental characterization of smooth body flow separation topography and topology on a two-dimensional geometry of finite span

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