Journal ArticleDOI
The mixing layer over a deep cavity at high-subsonic speed
TLDR
In this article, a high-speed schlieren technique was used to characterize the phase-averaged properties of the flow over a cavity at a Mach number 0.8, and it was shown that the formation of coherent vortices in the region close to the boundary layer separation has some resemblance to the collective interaction mechanism introduced by Ho & Huang (1982) to describe mixing layers subjected to strong sub-harmonic forcing.Abstract:
The flow over a cavity at a Mach number 0.8 is considered. The cavity is deep with an aspect ratio (length over depth) L/D = 0.42. This deep cavity flow exhibits several features that makes it different from shallower cavities. It is subjected to very regular self-sustained oscillations with a highly two-dimensional and periodic organization of the mixing layer over the cavity. This is revealed by means of a high-speed schlieren technique. Analysis of pressure signals shows that the first tone mode is the strongest, the others being close to harmonics. This departs from shallower cavity flows where the tones are usually predicted well by the standard Rossiter’s model. A two-component laser-Doppler velocimetry system is also used to characterize the phase-averaged properties of the flow. It is shown that the formation of coherent vortices in the region close to the boundary layer separation has some resemblance to the ‘collective interaction mechanism’ introduced by Ho & Huang (1982) to describe mixing layers subjected to strong sub-harmonic forcing. Otherwise, the conditional statistics show close similarities with those found in classical forced mixing layers except for the production of random perturbations, which reaches a maximum in the structure centres, not in the hyperbolic regions with which turbulence production is usually associated. An attempt is made to relate this difference to the elliptic instability that may be observed here thanks to the particularly well-organized nature of the flow.read more
Citations
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Computational aeroacoustics: progress on nonlinear problems of sound generation
Tim Colonius,Sanjiva K. Lele +1 more
TL;DR: A hierarchy of computational approaches that range from semi-empirical schemes that estimate the noise sources using mean-flow and turbulence statistics, to high-fidelity unsteady flow simulations that resolve the sound generation process by direct application of the fundamental conservation principles is discussed in this paper.
Journal ArticleDOI
Active control of flow-induced cavity oscillations
TL;DR: A review of active control of flow-induced cavity oscillations is presented in this paper, with emphasis on experimental implementation of open-and closed-loop control approaches, as well as the characteristics of various actuators, flow sensing and measurement, and control methodologies employed to date.
Journal ArticleDOI
Experimental Study of Shock Oscillation over a Transonic Supercritical Profile
TL;DR: In this paper, the authors describe a new experiment executed in the ONERA S3Ch transonic wind tunnel on shock oscillations over the OAT15A supercritical profile, which has allowed the precise definition of the conditions for buffet onset and the characterization of the properties of the periodic motion from unsteady surface pressure measurements.
Review of Active Control of Flow-Induced Cavity Resonance
TL;DR: A review of active control of flow-induced cavity oscillations is presented in this article, with emphasis on experimental implementation of open-and closed-loop control approaches, and the characteristics of various actuators, flow sensing and measurement, and control methodologies employed to date.
Journal ArticleDOI
Supersonic Cavity Flows and Their Control
TL;DR: A detailed experimental study of supersonic, Mach 2, flow over a three-dimensional cavity was conducted using shadowgraph visualization, unsteady surface pressure measurements, and particle image velocimetry as discussed by the authors.
References
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Journal ArticleDOI
On the identification of a vortex
Jinhee Jeong,Fazle Hussain +1 more
TL;DR: In this article, the authors propose a definition of vortex in an incompressible flow in terms of the eigenvalues of the symmetric tensor, which captures the pressure minimum in a plane perpendicular to the vortex axis at high Reynolds numbers, and also accurately defines vortex cores at low Reynolds numbers.
Journal ArticleDOI
Vortex pairing : the mechanism of turbulent mixing-layer growth at moderate Reynolds number
C. D. Winant,F. K. Browand +1 more
TL;DR: A mixing layer is formed by bringing two streams of water, moving at different velocities, together in a lucite-walled channel as mentioned in this paper, where dye is injected between the two streams just before they are brought together, marking the vorticitycarrying fluid.
Wind tunnel experiments on the flow over rectangular cavities at subsonic and transonic speeds
TL;DR: In this article, measurements have been made of the time average and unsteady pressures acting on the roof and behind a series of rectangular cavities set in the roof of the 2 ft x 1 tr ft transonic tunnel.
Journal ArticleDOI
Coherent structures and turbulence.
TL;DR: In this article, a general scheme for educing coherent structures in any transitional or fully turbulent flow is presented, based on smoothed vorticity maps in convenient flow planes, which recognizes patterns of the same mode and parameter size, and then phase-aligns and ensembles them to obtain coherent structure measures.