A numerical and experimental study of a transitional separation bubble

Häggmark, C. P.; Hildings, Casper; Henningson, Dan S.

doi:10.1016/s1270-9638(01)01110-5

Cited by 46 publications

(27 citation statements)

References 16 publications

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“…Furthermore, this is in good agreement with other relevant studies, e.g. Häggmark et al (2001) and Simoni et al (2012b).…”

Section: Spectral Content and Stability Characteristicssupporting

confidence: 93%

“…If, in addition, small perturbations to the baseline flow are assumed, it is possible to apply linear stability theory for estimating the most amplified unstable mode frequency. Häggmark et al (2001), Rist & Maucher (2002) and Marxen & Rist (2010) demonstrated that LST applied to the mean baseline flow can successfully reproduce experimental and numerical stability observations. It is generally accepted that disturbances developing in a LSB are initially convectively amplified via a Kelvin-Helmholtz instability mechanism, similar to free shear layers (Ho & Huerre 1984;Watmuff 1999;Marxen et al 2015).…”

Section: Introductionmentioning

confidence: 92%

“…Similarly to earlier studies (Häggmark et al 2001;Rist & Maucher 2002;Jones et al 2010;Marxen & Rist 2010;Yarusevych & Kotsonis 2017) the stability characteristics of the LSB mean flow field are investigated using linear stability theory (LST). The latter assumes local parallel flow and low amplitude wave-like disturbances.…”

Section: Linear Stability Theorymentioning

confidence: 99%

“…Finally, linear stability theory is employed in order to relate pertinent changes in stability characteristics to the changes in LSB dynamics. Since the aforementioned studies (Häggmark et al 2001;Rist & Maucher 2002;Marxen & Rist 2010) involving linear stability theory analysis only consider stability characteristics of the mean flow, a necessity rises of investigating dynamic stability, for which quasi-steady assumptions may be made. LST in the spatial formulation is, therefore, applied on phase-averaged velocity fields within a forcing cycle in order to assess changes in stability characteristics from bursting until recovery of the LSB to its unperturbed state.…”

Section: Introductionmentioning

confidence: 99%

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Response of a laminar separation bubble to impulsive forcing

2017

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The spatial and temporal response characteristics of a laminar separation bubble to impulsive forcing are investigated by means of time-resolved particle image velocimetry and linear stability theory. A two-dimensional impulsive disturbance is introduced with an AC dielectric barrier discharge plasma actuator, exciting pertinent instability modes and ensuring flow development under environmental disturbances. Phase-averaged velocity measurements are employed to analyse the effect of imposed disturbances at different amplitudes on the laminar separation bubble. The impulsive disturbance develops into a wave packet that causes rapid shrinkage of the bubble in both upstream and downstream directions. This is followed by bubble bursting, during which the bubble elongates significantly, while vortex shedding in the aft part ceases. Duration of recovery of the bubble to its unforced state is independent of the forcing amplitude. Quasi-steady linear stability analysis is performed at each individual phase, demonstrating reduction of growth rate and frequency of the most unstable modes with increasing forcing amplitude. Throughout the recovery, amplification rates are directly proportional to the shape factor. This indicates that bursting and flapping mechanisms are driven by altered stability characteristics due to variations in incoming disturbances. The emerging wave packet is characterised in terms of frequency, convective speed and growth rate, with remarkable agreement between linear stability theory predictions and measurements. The wave packet assumes a frequency close to the natural shedding frequency, while its convective speed remains invariant for all forcing amplitudes. The stability of the flow changes only when disturbances interact with the shear layer breakdown and reattachment processes, supporting the notion of a closed feedback loop. The results of this study shed light on the response of laminar separation bubbles to impulsive forcing, providing insight into the attendant changes of flow dynamics and the underlying stability mechanisms.

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“…Furthermore, this is in good agreement with other relevant studies, e.g. Häggmark et al (2001) and Simoni et al (2012b).…”

Section: Spectral Content and Stability Characteristicssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 92%

Section: Linear Stability Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Response of a laminar separation bubble to impulsive forcing

2017

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“…More recent studies [8][9][10][11][12] point out the difficulties to study the LSB because of the unsteadiness of the phenomenon and the dependence on the spectral components of the main flow turbulence. In the present work, IR thermography is proposed as a quantitative experimental technique to determine the three characteristic points of the LSB by analyzing the surface heat transfer coefficient with the heated-thin-foil technique [13].…”

Section: Introductionmentioning

confidence: 99%

A thermographic method to evaluate laminar bubble phenomena on airfoil operating at low Reynolds number

Cesini¹,

Ricci²,

Montelpare³

et al. 2002

Proceedings of the 2002 International Conference on Quantitative InfraRed Thermography

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The aim of this research is the study of the laminar boundary layer separation phenomena on aerodynamic bodies by infrared thermography. The presence and the size of laminar bubble are mainly observed. A thermographic method is adjusted to detect the presence and the longitudinal dimension of the laminar bubble. In this region the convective heat transfer coefficient is lower than in the surroundings, because of the recirculating flow. Heating the airfoil surface, the laminar bubble will appear warmer than the other zones and so it is possible to know its presence and position.

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Numerical Simulation of the Bursting of a Laminar Separation Bubble

Marxen

Henningson

High Performance Computing in Science and Engineering ’06

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A numerical and experimental study of a transitional separation bubble

Cited by 46 publications

References 16 publications

Response of a laminar separation bubble to impulsive forcing

Response of a laminar separation bubble to impulsive forcing

A thermographic method to evaluate laminar bubble phenomena on airfoil operating at low Reynolds number

Numerical Simulation of the Bursting of a Laminar Separation Bubble

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