Influence of localised double suction on a turbulent boundary layer

Oyewola, Olanrewaju M.; Djenidi, L.; Antonia, R. A.

doi:10.1016/j.jfluidstructs.2006.11.006

Cited by 7 publications

(9 citation statements)

References 14 publications

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“…and Oyewola et al, [36][37][38] etc. Simulations have shown that even a low amount of flow rate (up to 10 % of free stream velocity) is sufficient for altering the boundary layer structure.…”

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confidence: 94%

Active Flow Control Methods for the Reduction of Trailing Edge Noise

Szoke

Azarpeyvand

2017

23rd AIAA/CEAS Aeroacoustics Conference

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. The possibility of trailing edge noise reduction using active flow control is addressed in this paper. The boundary layer is altered with the help of uniform perpendicular and inclined flow injection and suction on a long flat plate upstream of a sharp trailing edge. The flow quantities have been measured using particle image velocimetry, hot-wire anemometry, and the surface pressure fluctuations using flush mounted miniature pressure transducers. It was shown that the proposed flow control methods are capable of reducing the noise over a wide range of frequencies. It was also revealed that the perpendicular blowing is effective in shifting the energy containing turbulent structures away from the wall, resulting in a significant reduction in the surface pressure spectra. The inclined blowing control method was capable of further reducing the surface pressure spectra, while maintaining low input power requirement. The perpendicular suction control was shown to be effective in the reduction of pressure fluctuations in the mid frequency regions, which quickly penetrates to the lower frequency downstream. The inclined suction control has also lead to significant reductions in the surface pressure fluctuations over a wide range of frequencies, while the required suction rate was kept considerably low. It has also been shown that the proposed active flow control methods can reduce the spanwise correlation length of the turbulent structures near the trailing edge. In general, results have shown that all proposed active flow control techniques can effectively alter the boundary layer structure and reduce trailing edge noise. Nomenclature

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confidence: 94%

Active Flow Control Methods for the Reduction of Trailing Edge Noise

Szoke

Azarpeyvand

2017

23rd AIAA/CEAS Aeroacoustics Conference

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“…Their work was followed by a series of experimental and numerical investigations on the effect of concentrated flow suction from a turbulent boundary layer at low Reynolds numbers, see Antonia et al [45], Oyewola et al [46][47][48], Park and Choi [49] and a more recent work of Kametani et al [50]. These studies [45][46][47][48]50] covered a wide range of suction rates (σ), which they defined as the ratio of momentum flux of flow suction and momentum flux of the boundary layer. A number of studies [46] reported that flow suction can re-laminarise the boundary layer at moderate momentum thickness Reynolds numbers (Re θ < 660).…”

Section: Introductionmentioning

confidence: 99%

Influence of boundary layer flow suction on trailing edge noise generation

Szőke

Fiscaletti

Azarpeyvand

2020

Journal of Sound and Vibration

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The effect of uniform inclined flow suction on an equilibrium turbulent boundary layer developing over a flat plate is experimentally investigated for aeroacoustic purposes. Simultaneous measurements of streamwise velocity with hot-wire anemometry, and surface pressure fluctuations using flush-mounted microphones were performed at various locations downstream of the flow control treatment. The paper discusses the effects of flow suction on the turbulent quantities describing the boundary layer, and the associated hydrodynamic pressure field to assess the effects of flow suction on trailing edge noise generation. Two parameters were varied, the inclination of the flow suction velocity (α) and the flow suction severity (σ). The former is the angle of flow suction with respect to the free-stream flow (α = 30 • , 50 • , 70 • and 90 • ), while the latter is the ratio of momentum deficit within the boundary layer to the momentum of flow suction (σ = 2.5 − 9.1). Flow suction reduces the height of the boundary layer, which results in an increase of mean shear. The flow energy content within the boundary layer is reduced by suction with the most significant amount of reduction is observed within the logarithmic region. A moderate energy increase is observed in the buffer layer. These effects strengthen with growing suction severity until σ ≈ 6. Above this point, no further changes are observed in the turbulent quantities. The reduction in the size and energy content of the logarithmic layer is responsible for the reduction of the surface pressure fluctuations at mid-frequencies, while the increased energy content in the buffer layer increases the pressure spectral content at high frequencies. The estimates of the far-field trailing edge noise show that flow suction leads to a noise reduction at mid-frequencies with penalties observed at low and high frequencies. Flow suction at an angle of α = 70 • and σ ≈ 6 exhibits the best performance in reducing the estimated far-field overall noise levels. Above this point, further increasing the flow suction severity does not provide any additional noise reduction benefits.

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“…The underlying mechanism leading to the reduction of the energy content was investigated in previous computational and experimental studies. As reported in Refs., [39][40][41][42][43][44] flow suction increases viscous diffusion, which was found to be responsible for the break-up of turbulent structures. As a result of this, flow suction was found to reduce the turbulence intensities and Reynolds shear stresses.…”

Section: Root Mean Square Velocity Profilesmentioning

confidence: 99%

“…This effect is an indication of reduced turbulent activity within the boundary layer. Their work was followed by a series of experimental investigations on the effect of concentrated flow suction from a turbulent boundary layer at low Reynolds numbers, see Antonia et al 39 and Oyewola et al [40][41][42] The authors applied a wide range of suction rates (σ), which they defined as the ratio of momentum flux of flow suction and momentum flux of the boundary layer. Later, several studies on the effects of flow suction on a turbulent boundary layer reported that downstream of the flow control section the turbulent flow shows laminar behavior.…”

Section: Introductionmentioning

confidence: 99%

“…Later, several studies on the effects of flow suction on a turbulent boundary layer reported that downstream of the flow control section the turbulent flow shows laminar behavior. [39][40][41][42][43] The streamwise length of the plate in the aforementioned experimental campaigns was sufficient to enable the flow recovery downstream of flow suction. At a suction rate of σ = 2.6, the boundary layer required a streamwise distance of 20δ 0 , where δ 0 is the thickness of the undisturbed boundary layer, to recover its original state.…”

Section: Introductionmentioning

confidence: 99%

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Uniform Suction for the Reduction of the Trailing-Edge Noise

Szoke

Azarpeyvand²,

Fiscaletti³

2019

25th AIAA/CEAS Aeroacoustics Conference

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Uniform inclined suction from a spanwise slot is applied upstream of a trailing edge on a zero pressure gradient flat plate with the aim of reducing trailing edge noise. The effects of the flow treatment on the turbulence statistics are experimentally investigated downstream of the flow control section using hot-wire anemometry. Surface pressure measurements from flush-mounted microphones are used to estimate the far-field trailing edge noise. The area of the flow control is kept constant, while the flow suction velocity and the angle of suction are varied. We examine four angles of flow suction velocity, namely α = 30 • , 50 • , 70 • and 90 • alongside a wide range of flow control severities. It is found that flow suction changes the overall structure of the flow. Both the boundary layer thickness and the momentum thickness increases as a result of flow suction. The mean velocity profiles nondimensionalized by the inner units show that flow suction increases the extent of the viscous region, while the logarithmic region progressively reduces its size with increasing the flow suction severity. At sufficiently high suction rates, the logarithmic region disappears, which is an evidence of flow laminarisation. Flow suction efficiently reduces the flow energy content within the entire span of the boundary layer. The estimated far-field trailing edge noise is reduced in the range of frequencies between 200 Hz and 1-2 kHz, with the highest levels of estimated noise reduction obtained at an angle of flow suction of α = 70 • , at a suction rate high enough to achieve laminarisation.

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Influence of localised double suction on a turbulent boundary layer

Cited by 7 publications

References 14 publications

Active Flow Control Methods for the Reduction of Trailing Edge Noise

Active Flow Control Methods for the Reduction of Trailing Edge Noise

Influence of boundary layer flow suction on trailing edge noise generation

Uniform Suction for the Reduction of the Trailing-Edge Noise

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