The delay of turbulent boundary layer separation by oscillatory active control

Katz, Y.; Nishri, B.; Wygnanski, I.

doi:10.1063/1.857555

Cited by 41 publications

(12 citation statements)

References 3 publications

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“…It should also be noted that a -~45% reduction in Y0 (relative to the unexcited flow) was observed when the flow was excited. Such phenomena were already disclosed by Katz et al (1989).…”

Section: Frequency Response Validity Testmentioning

confidence: 74%

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The ladder probe: reverse flow measurements with a hot-wire rake

Sokolov

Ginat

1992

Experiments in Fluids

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A probe consisting of a ladder-like rake of hot wires was developed in order to facilitate velocity measurements in reverse flow situations. Hot-wire signals obtained by the ladder probe capture a substantial section of the instantaneous velocity profile which includes the point where the change of direction occurs. These signals were processed to obtain the thickness of the reverse flow layer through a procedure which detects the point of zero velocity. The procedure was validated through a conservation-type consistency test, frequency response and periodicity tests, and by comparison with results in the literature. Characterization of a turbulent separated layer is discussed. Three different parameters are used to measure the thickness of the reverse flow region: cross streamwise coordinate of the point of zero average velocity, average coordinate of zero velocity points, and the coordinate of the 50% flow direction (forward or reversed) probability point. Relationships between these parameters and physical interpretation of their relevance to the separated flow field are also discussed.

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“…It should also be noted that a -~45% reduction in Y0 (relative to the unexcited flow) was observed when the flow was excited. Such phenomena were already disclosed by Katz et al (1989).…”

Section: Frequency Response Validity Testmentioning

confidence: 74%

“…Phase-locked average velocities revealed (Katz et al 1989) that the forcing frequency information is retained throughout the flow field. It was therefore expected that Yo (t) will also exhibit oscillatory motion at the forcing frequency or its sub-harmonics.…”

Section: Frequency Response Validity Testmentioning

confidence: 99%

The ladder probe: reverse flow measurements with a hot-wire rake

Sokolov

Ginat

1992

Experiments in Fluids

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“…A flat plate case is considered 3 at Re x = U∞ x ν = 4.3 10 8 , at which position the boundary layer has the following characteristics:…”

Section: Interpretation and Usementioning

confidence: 99%

“…The present paper will consider only the case of pulsating jets, although there seems to exist a similarity between these two flow control methods. There exists also ample experimental evidence in the literature, [3,7,18,21], for this kind of flow control. A recent detailed review is provided in [2] mentioned above.…”

Section: Introductionmentioning

confidence: 96%

Using Stability Theory to Analyse Configurations of Pulsed Jets for Flow Control

Skamnakis

Papailiou

2007

Flow Turbulence Combust

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During the last decade, efforts for simulating active flow control behavior by the use of pulsating jets have multiplied. In the present work, a URANS is used mostly for simulation, where the resulting flow characteristics can be reproduced with fair but adequate accuracy for engineering applications. This computational tool provides information concerning the effect on the flow, of the flow control. An additional computational tool is introduced, that of flow stability analysis, which allows to optimize the frequency and the position of the actuators (here pulsating jets). This tool will be developed through flow stability arguments. Both tools will be used within the context of the present paper and for reasons explained below, for suppressing only flow separation in internal flow cases. Once the computational tools are described/developed, they will be applied to a specific case. The optimization procedure will be demonstrated and discussed.

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“…Reynolds and Carr (1985) interpreted the findings of Francis et al from a viewpoint of vorticity dynamics. Recently, Katz et al (1989) reported that by installing an oscillating plate at the apex of a wedge, the original separated flow could be suppressed by the introduction of two-dimensional small-amplitude perturbation. Koga (1983), Reisenthel et al (1985) and Nagib et al (1985) have shown that by installing an oscillating flap in the separated region behind a backward-facing step the reattachment length could be reduced by up to 60%.…”

Section: Introductionmentioning

confidence: 99%

Flow structures behind a vertically oscillating fence immersed in a flat-plate turbulent boundary layer

Miau

Chen

1991

Experiments in Fluids

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A phase-averaging technique was employed to study the evolution of flow behind an oscillating bluff plate immersed in a fiat-plate turbulent boundary layer. The experiments were performed for a reduced frequency of 0.0044. The large-scale disturbance generated by the plate developed to an organized form over 20 maximum plate height and then diffused rapidly, as quantified by the ratio of Reynolds stress of the phase-averaged fluctuation to that of the total fluctuation. The small-scale fluctuations embedded in the large-scale disturbance were almost removed by phase averaging. However, their contributions in Reynolds stress and kinetic energy were pronounced along the path of the core of the large-scale structure.

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The delay of turbulent boundary layer separation by oscillatory active control

Abstract: Active control of turbulent boundary layer noise transmission through an aeroelastic plate

Cited by 41 publications

References 3 publications

The ladder probe: reverse flow measurements with a hot-wire rake

The ladder probe: reverse flow measurements with a hot-wire rake

Using Stability Theory to Analyse Configurations of Pulsed Jets for Flow Control

Flow structures behind a vertically oscillating fence immersed in a flat-plate turbulent boundary layer

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