Attenuation of sweep events in a turbulent boundary layer using micro-cavities

Silvestri, Anton; Ghanadi, Farzin; Arjomandi, Maziar; Cazzolato, B.; Zander, Anthony C.

doi:10.1007/s00348-017-2345-7

Cited by 24 publications

(57 citation statements)

References 25 publications

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“…range in the log-region than that for u rms /U τ , which might be as a result of the wall-normal velocity interactions happening through the micro-cavity holes. Moreover, the lower values of u rms /U τ indicate lower turbulence intensitis in the presence of the micro-cavities, supporting the previous observations [10].…”

Section: Effects On the Velocity Fluctuationssupporting

confidence: 89%

“…Recently, the experimental work at the University of Adelaide on the application of the micro-cavity array [13,10,11] has shown interesting results. This method uses an array of holes, with size of the order of the small viscous length scales on a surface and are backed up by a large backing cavity common to all the holes.…”

Section: Introductionmentioning

confidence: 99%

“…The wind-tunnel experiments show that, in the presence of the array, the sweep events are attenuated by ∼ 7% [11]. The diameter of the holes in the array has been found to affect the amount of reduction in the sweep events [10]. Moreover, studies on the synthetic jet created from an array of orifices report that the optimal spanwise and streamwise spacing between the holes is of approximately 1000 and 100 viscous length scales [2,6].…”

Section: Introductionmentioning

confidence: 99%

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Reduction in the Turbulent Instabilities in a Boundary Layer using Micro-cavities

Bhat¹,

Silvestri²,

Cazzolato³

et al. 2020

Australasian Fluid Mechanics Conference (AFMC)

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The turbulence intensities and shear stresses in a turbulent boundary layer (TBL) are primarily associated with the presence of coherent structures, such as sweep and ejection events. Recent experiments using a passive method of controlling the TBL using micro-cavities have reported reduction in the coherent structures by ∼ 7%. However, the mechanism behind the reduction has not been identified due to the complexity of the near-wall small scale interactions. The present work presents outcomes of the direct numerical simulations of the turbulent boundary layer over the bottom surface of a channel with the aim of focussing on the effects on the velocity fluctuations and the shear stresses. It is found that the application of microcavities on the surface results in the reduced turbulent instabilities in the near-wall flow region.

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Section: Effects On the Velocity Fluctuationssupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reduction in the Turbulent Instabilities in a Boundary Layer using Micro-cavities

Bhat¹,

Silvestri²,

Cazzolato³

et al. 2020

Australasian Fluid Mechanics Conference (AFMC)

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“…He found that the perforate constant is proportional to the ratio of the perforation radius to the viscous boundary layer thickness inside the holes, which can determine the characteristic of acoustic impedance and the frequency of the structure absorbed by the MPP. Silvestri et al 24,25 have showed that the use of micro-cavity array on a flat-plate, which is an extension of the work conducted by Maa, 23 leads to significant reduction of the turbulence energy and the sweep intensity in the turbulent boundary layer. It was also shown that the use of the micro-cavities surface can dampen the coherent structures and disrupt the bursting cycle, responsible for the shear stress and the viscous drag in the inner region of the boundary layer.…”

Section: Nomenclature C Pmentioning

confidence: 89%

Boundary layer flow interaction with a permeable wall

et al. 2018

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Wall pressure coherence between two pressure transducers Λ p Spanwise coherence length (mm) Φ Cross-power spectral density function ξ x , ξ y , ξ z Streamwise, vertical, and spanwise separation distance (mm) PPI Pores per inch PSD Power spectral density I. INTRODUCTION The possibility of controlling turbulent flows, reducing the energy content of flow structures, and suppressing aerodynamically generated noise at the source is of great academic and

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“…Ejection events generate approximately 70% of the total stresses in the inner wall region, while sweep events account for the remaining 30% [12][13][14] and consequently are deemed to be very important during turbulence generation. One technique that has been investigated to control these structures to reduce skin friction drag and has showed promise is the micro-cavity array [4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

The Control of a turbulent boundary layer by the application of a micro-cavity array

Silvestri¹,

Jafari²,

Bhat³

et al. 2020

Australasian Fluid Mechanics Conference (AFMC)

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Micro-cavity arrays have been identified as a potential passive device to disrupt and capture sweep events, which are responsible for the Reynolds stresses in the boundary layer. The application of micro-cavity arrays for drag reduction was proposed 10 years ago by the University of Adelaide [1-8] and the present article summarises the findings of its investigation during this time. These results are based on data obtained through comprehensive experimental investigations, which has shown that the application of microcavity arrays can achieve a reduction of up to 16% in turbulence energy production within the wall-bounded turbulent flow at low Reynolds numbers [7]. This reduction of turbulent production can be correlated to a skin friction drag reduction of approximately 3% [9]. In a more recent work, a direct numerical modelling investigation into the shared common backing cavity arrangement has been conducted [8]. The results revealed that a maximum reduction in the wall shear stresses of 7.12% could be achieved, which lasted for a considerable distance downstream of the cavity array.

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Attenuation of sweep events in a turbulent boundary layer using micro-cavities

Cited by 24 publications

References 25 publications

Reduction in the Turbulent Instabilities in a Boundary Layer using Micro-cavities

Reduction in the Turbulent Instabilities in a Boundary Layer using Micro-cavities

Boundary layer flow interaction with a permeable wall

The Control of a turbulent boundary layer by the application of a micro-cavity array

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