The effects of stream turbulence on separation bubbles

Hillier, R.; Cherry, Nigel

doi:10.1016/0167-6105(81)90007-6

Cited by 165 publications

(84 citation statements)

References 5 publications

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“…Spectra of velocity fluctuations in the separated shear layer exhibit strong peaks at the frequency of vortex shedding [10,17,18,26], but can have additional peaks at low frequencies which are associated with bubble 'flapping' [32,48,50,53,54], and/or peaks at the subharmonic of the shedding frequency which are associated with vortex merging [17,20,55]. Bubble flapping is associated with fluctuations within the separation bubble that are not related to the shedding of shear layer vortices [17], and result in an unsteady up and down motion of the separated shear layer [31,48].…”

Section: Figure 21mentioning

confidence: 99%

Effects of free-stream turbulence intensity on laminar separation bubbles

Istvan

Kurelek

Yarusevych

2016

46th AIAA Fluid Dynamics Conference

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Section: Figure 21mentioning

confidence: 99%

Effects of free-stream turbulence intensity on laminar separation bubbles

Istvan

Kurelek

Yarusevych

2016

46th AIAA Fluid Dynamics Conference

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“…FST results in an earlier transition to turbulence and hence usually a shorter separation bubble (Hillier and Cherry, 10 Kalter and Fernholz, 11 Yang and Abdalla, 4 and Castro and Haque 12 ). McAuliffe and Yaras 5 studied the effect of elevated FST (1.45% at separation) on a laminar separated boundary layer due to an adverse pressure gradient over a flat plate.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of the primary instability in a separated boundary layer transition under elevated free-stream turbulence

Langari

Yang

2013

Physics of Fluids

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Numerical studies of laminar-to-turbulent transition in a separation bubble subjected to two free-stream turbulence levels (FST) have been performed using Large-Eddy Simulation (LES). Separation of the laminar boundary layer occurs at a curvature change over a plate with a semi-circular leading edge at Re = 3450 based on the plate thickness and the uniform inlet velocity. A numerical trip is used to produce the targeted free-stream turbulence levels and the decay of free-stream turbulence is well predicted. A dynamic sub-grid-scale model is employed in the current study and a good agreement has been obtained between the LES results and the experimental data. Detailed analysis of the LES data has been carried out to investigate the primary instability mechanism. The flow visualisations and spectral analysis of the separated shear layer reveal that the 2D Kelvin-Helmholtz instability mode, well known to occur at low FST levels, is bypassed at higher levels leading to earlier breakdown to turbulence. C 2013 AIP Publishing LLC.[http://dx

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“…This difference in σ u /u * might be attributed to the lack of large-scale "inactive motion" in the boundary layer (Raupach et al, 1986). Nevertheless, the structure of the separation bubble is mostly dependent on the smallscale turbulent characteristics of the freestream near separated flow regions (Hillier and Cherry, 1981).…”

Section: Experimental Designmentioning

confidence: 99%

“…Numerous studies have shown that accurately simulating freestream turbulence is a necessary condition to achieving dynamic similitude in the boundary layer wind tunnel (BLWT), particularly for characterizing pressure extrema in separated flow regions (e.g., Tieleman et al, 1978;Hillier and Cherry, 1981;Gartshore, 1984;Tieleman, 1992;St Pierre et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Effects of Freestream Turbulence on the Pressure Acting on a Low-Rise Building Roof in the Separated Flow Region

Fernández-Cabán

Masters

2018

Front. Built Environ.

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This paper presents the experimental design and subsequent findings from a series of experiments in a large boundary layer wind tunnel to investigate the variation of surface pressures with increasing upwind terrain roughness on low-rise buildings. Geometrically scaled models of the Wind Engineering Research Field Laboratory experimental building were subjected to a wide range of turbulent boundary layer flows, through precise adjustment of a computer control terrain generator called the Terraformer. The study offers an in-depth examination of the effects of freestream turbulence on extreme pressures under the separation "bubble" for the case of the wind traveling perpendicular to wall surfaces, independently confirming previous findings that the spatial distribution of the peaks is heavily influenced by the mean reattachment length. Further, the study shows that the observed peak pressures collapse if data are normalized by the mean reattachment length and a non-Gaussian estimator for peak velocity pressure.

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The effects of stream turbulence on separation bubbles

Cited by 165 publications

References 5 publications

Effects of free-stream turbulence intensity on laminar separation bubbles

Effects of free-stream turbulence intensity on laminar separation bubbles

Numerical study of the primary instability in a separated boundary layer transition under elevated free-stream turbulence

Effects of Freestream Turbulence on the Pressure Acting on a Low-Rise Building Roof in the Separated Flow Region

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