Self-excited oscillations of turbulent inflow along a perforated plate

Özalp, Coşkun; Pınarbaşı, Ahmet; Rockwell, D.

doi:10.1016/s0889-9746(03)00045-8

Cited by 24 publications

(12 citation statements)

References 13 publications

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“…27 All of the foregoing investigations of flow past perforated plates or louvers have centered on the instabilities, or unsteady events, across an individual perforation or adjacent louvers, and in the event that an organized oscillation is present, it has a wavelength of the order of the perforation diameter or louver gap. As a complement to these investigations, Celik and Rockwell 28 and Ozalp, Pinarbasi and Rockwell 29 have demonstrated, for laminar and fully developed turbulent inflow boundary layers, respectively, generation of a highly coherent long wavelength instability, which scales as the length of the plate, rather than according to an individual perforation. Such oscillations are purely hydrodynamic and occur in absence of any acoustic-resonant or wallelasticity effects.…”

Section: A Previous Related Investigationsmentioning

confidence: 92%

“…Further details are provided by Celik and Rockwell 28 and Ozalp, Pinarbasi and Rockwell. 29 As indicated, the perforated plate is bounded by a large-scale, rigid closed cavity having thick walls, in order to preclude the effects of wall elasticity, i.e., wall-flexing for the relatively low flow velocities of this investigation on its backside. Variations of the effective length L of the perforated plate are achieved by translating a plate with a sharp edge along the surface of the perforated plate.…”

Section: Experimental System and Techniquesmentioning

confidence: 99%

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Coupled oscillations of flow along a perforated plate

Çelik

Rockwell

2004

Physics of Fluids

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Turbulent shear flow past a perforated plate bounded by a closed cavity can give rise to highly coherent oscillations, which have a wavelength of the order of the plate length. The present investigation focuses on the coupling between unsteady events on either side of the plate when the oscillations are self-sustaining. A cinema technique of high-image-density particle image velocimetry, which provides a space-time representation of the unsteadiness at a large number of locations over entire planes, is employed to characterize the distinctively different patterns of flow structure on the back ͑low-speed͒ side of the plate relative to those on the front ͑high-speed͒ side. Global cross-spectral analysis leads to patterns of spectral peaks and phase variations, along and across the plate. This approach, along with complementary types of image evaluation, delineates the physics of the oscillations, which include downstream propagating disturbances along either side of the plate and a coherent region of unsteadiness at its trailing-edge. On the backside of the plate, a sequence of upstream-oriented, pulsatile jets are formed, and the time-averaged flow pattern is a counterflow wall jet.

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Section: A Previous Related Investigationsmentioning

confidence: 92%

Section: Experimental System and Techniquesmentioning

confidence: 99%

Coupled oscillations of flow along a perforated plate

Çelik

Rockwell

2004

Physics of Fluids

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“…Building on the work of Howe (1979), Eldredge & Dowling (2003) considered the effectiveness of a cylindrical perforated liner with mean bias flow in its absorption. Ozalp, Pinarbasi & Rockwell (2003) studied the self-excited oscillations of a turbulent boundary layer along a perforated plate closed by a cavity using particle image velocimetry (PIV). Ma, Slaboch & Morris (2009) also investigated the detailed fluid dynamic characteristics of a flow-excited Helmholtz resonator using PIV and proposed a predictive methodology for the corresponding measurements.…”

Section: Literature Reviewmentioning

confidence: 99%

Numerical investigation of a honeycomb liner grazed by laminar and turbulent boundary layers

Zhang

Bodony

2016

J. Fluid Mech.

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Direct numerical simulations are used to study the interaction of a cavity-backed circular orifice with grazing laminar and turbulent boundary layers and incident sound waves. The flow conditions and geometry are representative of single degree-of-freedom acoustic liners applied in the inlet and exhaust ducts of aircraft engines and are the same as those from experiments conducted at NASA Langley. The simulations identify the fluid mechanics of how the sound field and state of the grazing boundary layer impact the in-orifice flow and suggest a simple flow analogy that enables scaling estimates. From the scaling estimates the simulations are then used to develop reduced-order models for the in-orifice flow and a time-domain impedance model is constructed. The liner is found to increase drag at all conditions studied by an amount that increases with the incident sound pressure amplitude.

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“…Most importantly, Jordan redefined the no oscillation/oscillation boundary of Sarohia (1975) to a no feedback/feedback boundary for shallow cavities covered by a perforated lid. Ozalp et al (2003) subsequently extended the experiments of Celik and Rockwell (2002) to investigate the same phenomena, but approached by a turbulent boundary layer. For hole diameters D/y o 5 4, they visualised large-scale coherent vortices well above the fine-scale structures of turbulence.…”

Section: Introductionmentioning

confidence: 99%

Attenuating the large-scale turbulent oscillations sustained by shallow cavities with a perforated lid

Jordan

2009

International Journal of Computational Fluid Dynamics

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Marine engineers face a challenging problem when designing recessed cavities that require perforated covers. Under certain geometric and kinematic conditions, the separated shear layers directly above the perforations support the spatial maturity of periodic large-scale structures. Intermittent spoilers attenuate the structure's maturity by interrupting communication between the shear layer and the adjacent inner cavity, but this success fails during transient flow conditions. In the far-field, the corresponding noise pulse is easily detectable. Evolutionary growth of the streamwise structures originates from small Kelvin-Helmholtz (K-H) waves within the shear layers just after separation and are sustained by a pressure feedback mechanism that occurs within the cavity itself. Herein, the resolved physics from large-eddy simulations along with the previous experimental evidence show analogous fundamental characteristics between the open and perforated covered cavities regardless of whether upstream separation is laminar or turbulent. These quantitative analogies are equally similar for lids perforated by staggered circular holes or slots that are tightly spaced in the streamwise direction. An alternative measure permits formation of the K-H waves, then successfully mitigates their streamwise growth by elongating the distance between perforations. This latter corrective measure reverses the mean resultant lid force to the preferred outboard direction.

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Self-excited oscillations of turbulent inflow along a perforated plate

Cited by 24 publications

References 13 publications

Coupled oscillations of flow along a perforated plate

Coupled oscillations of flow along a perforated plate

Numerical investigation of a honeycomb liner grazed by laminar and turbulent boundary layers

Attenuating the large-scale turbulent oscillations sustained by shallow cavities with a perforated lid

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