Journal ArticleDOI
Unsteady flow phenomena over delta wings at high angle of attack
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In this article, the authors show that coherent pressure fluctuations observed on delta wings are due to the helical mode instability of the vortex breakdown flow field, which implies increasing wavelength in the streamwise direction.Abstract:
Experiments show that coherent pressure fluctuations observed on delta wings are due to the helical mode instability of the vortex breakdown flowfield. No dominant frequency in the spectra of pressure fluctuations on the wing surface was observed after the breakdown reached the apex of the wing, although the vortex shedding could be detected in the wake. Measurements of pressure fluctuations at different streamwise locations on the wing suggest that the dimensionless frequency fx/U^ is nearly constant for a given geometry, which implies increasing wavelength in the streamwise direction. For different wings, this nondimensional frequency is shown to be a function of nondimensional circulation T/U^x only. Both the wavelength of the disturbances and the core radius increase with the nondimensional circulation at a fixed streamwise location. The wavelength normalized by the core radius is around 3-4, which is much smaller than the predictions for the Q vortex.read more
Citations
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Unsteady aerodynamics of nonslender delta wings
TL;DR: In this article, a review of the aerodynamic properties of nonslender delta wings is presented, covering topics of shear layer instabilities, structure of non-slender vortices, breakdown, maneuvering wings, and fluid/structure interactions.
Journal ArticleDOI
Vortex-body interactions
TL;DR: In this paper, the authors focus on the underlying flow physics, with the aim of clarifying the origin of the induced loading of vortex interactions and developing creative strategies, distinct from those traditionally employed for control of unstable shear flows.
Journal ArticleDOI
Review of Unsteady Vortex Flows over Slender Delta Wings
TL;DR: In this article, the authors defined the aspect ratio, amplitude ratio, and amplitude ratio as the probability density function of velocity function of the chord length and the wave number in angular direction.
Journal ArticleDOI
Validation of OpenFOAM numerical methods and turbulence models for incompressible bluff body flows
TL;DR: A verification and validation study was performed using the open source computational fluid dynamics solver OpenFOAM version 2.0 for incompressible bluff body fluid flows, which shows mostly monotonic convergence with averaged grid uncertainty.
Journal ArticleDOI
Flow Structure on a Delta Wing of Low Sweep Angle
B. Yaniktepe,Donald Rockwell +1 more
TL;DR: In this article, the instantaneous and averaged flow structure of a delta wing of low sweep angle was investigated using a technique of high-image-density particle image velocimetry, where the authors focused on crossflow planes, where vortex breakdown and stall occur, and the identification of buffeting mechanisms in these regions.
References
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Journal ArticleDOI
The stability of a trailing line vortex. Part 1. Inviscid theory
TL;DR: The inviscid stability of swirling flows with mean velocity profiles similar to that obtained by Batchelor (1964) for a trailing vortex from an aircraft is studied with respect to infinitesimal non-axisymmetric disturbances as discussed by the authors.
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Vortex breakdown on slender sharp-edged wings
D. L. Kohlman,W. H. Wentz +1 more
TL;DR: Vortex breakdown on slender sharp edged and modified delta wings with varying sweep angles investigated in wind tunnel using schlieren system for flow visualization as discussed by the authors, using Schlieren-based flow visualization.
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Spectral characteristics of vortex breakdown flowfields
A. K. Garg,Sidney Leibovich +1 more
TL;DR: In this paper, an anemometer measurement of the wakes of vortex breakdowns of bubble and spiral types is described, which correspond closely to theoretical predictions of the linearly most unstable normal modes of the time-averaged mean flow profiles.
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Observations of oscillatory motion in certain swirling flows
TL;DR: In this paper, a descriptive experimental study was made in both air and water of the temporally periodic motion that occurs in the vortex whistle and cyclone separator, which can be described in terms of an oscillator that derives its energy from hydrodynamic instability of the steady swirling flow and whose frequency is determined by an angular velocity characteristic of this steady flow.
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Observations of unsteady flow arising after vortex breakdown
John J. Cassidy,Henry T. Falvey +1 more
TL;DR: In this article, the authors describe an experimental study of the occurrence, frequency and peak-to-peak amplitude of the wall pressure generated by a helical vortex in rotating flow moving axially through a straight tube.