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Starting vortex

About: Starting vortex is a research topic. Over the lifetime, 4785 publications have been published within this topic receiving 100419 citations.


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TL;DR: In this paper, the three-dimensional nature of vortex shedding from a square cylinder in the vicinity of a solid wall is investigated for a Reynolds number of 18'900 as a function of the gap height, S/D.
Abstract: The three-dimensional nature of turbulent vortex shedding from a square cylinder in the vicinity of a solid wall is investigated for a Reynolds number of 18 900 as a function of the gap height, S/D. Spanwise surface pressure measurements on the cylinder faces and on the solid wall are complemented by velocimetry data. It is observed that parallel and oblique shedding modes arise naturally. The number of vortex dislocations is clearly related to the variations in the oblique shedding angle. Dislocations occur with increasing probability as the gap height is decreased to S/D≈0.7. The dislocations are strongly associated with Type A instabilities and vortex splitting, which contribute significantly to phase-jitter. For gap heights close to that for vortex shedding suppression (0.5

58 citations

01 Sep 1972
TL;DR: In this paper, an investigation was conducted to determine the flow field and aerodynamic effects of leading edge serrations on a two-dimensional airfoil at a Mach number of 0.13.
Abstract: An investigation was conducted to determine the flow field and aerodynamic effects of leading-edge serrations on a two-dimensional airfoil at a Mach number of 0.13. The model was a NACA 66-012 airfoil section with a 0.76 m (30 in.) chord, 1.02 m (40 in.) span, and floor and end plates. It was mounted in the Ames 7- by 10-Foot Wind Tunnel. Serrated brass strips of various sizes and shapes were attached to the model in the region of the leading edge. Force and moment data, and photographs of tuft patterns and of oil flow patterns are presented. Results indicated that the smaller serrations, when properly placed on the airfoil, created vortices that increased maximum lift and angle of attack for maximum lift. The drag of the airfoil was not increased by these serrations at airfoil angles of attack near zero and was decreased at large angles of attack. Important parameters were serration size, position on the airfoil, and spacing between serrations.

58 citations

Journal ArticleDOI
TL;DR: In this paper, a theory for the balanced evolution of a small-amplitude, small-scale wave field in the presence of an axisymmetric vortex initially in gradient-wind balance and the accompanying changes induced in the vortex by the azimuthally averaged wave fluxes is presented.
Abstract: A formal theory is presented for the balanced evolution of a small-amplitude, small-scale wave field in the presence of an axisymmetric vortex initially in gradient-wind balance and the accompanying changes induced in the vortex by the azimuthally averaged wave fluxes. The theory is a multi-parameter, asymptotic perturbation expansion for the conservative, rotating, f-plane, shallow-water equations. It extends previous work on Rossby-wave dynamics in vortices and more generally provides a new perspective on wave/mean-flow interaction in finite Rossby-number regimes. Some illustrative solutions are presented for a perturbed vortex undergoing axisymmetrization.

58 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that in the fluid analogue, a drain is not required in order for a vortex to scatter sound superradiantly, and this effect may occur even when the fluid density drops to zero at the vortex core, as is the case in a Bose-Einstein condensate.
Abstract: Sound waves scattered from a hydrodynamic vortex may be amplified. Such superradiant scattering follows from the physical analogy between spinning black holes and hydrodynamic vortices, as spinning black holes have an ergoregion within which low frequency waves may be scattered with increased amplitude. While black holes also have an event horizon, a fluid's analogous sonic horizon requires the vortex to have a central drain, which may be challenging to produce experimentally. We show that in the fluid analogue, a drain is not required in order for a vortex to scatter sound superradiantly. Furthermore, this effect may occur even when the fluid density drops to zero at the vortex core, as is the case in a Bose–Einstein condensate. We also consider engineering the density profile, using repulsive light forces, to extend the validity of the hydrodynamic approximation towards the vortex core.

58 citations

Journal ArticleDOI
TL;DR: In this paper, the response of a Hill's spherical vortex to an irrotational axisymmetric small perturbation is examined on the assumption that viscous diffusion of vorticity is negligible.
Abstract: The response of a Hill’s spherical vortex to an irrotational axisymmetric small perturbation is examined on the assumption that viscous diffusion of vorticity is negligible. The problem of determining the response is first reduced to a system of differential equations for the evolution of the Legendre coefficients of the disturbance stream function. This system is then solved approximately and it is shown that, if the initial disturbance is such as to make the vortex prolate spheroidal, the vortex detrains a fraction $c of its original volume, where e is the fractional extension of the axis of symmetry in the imposed distortion. The detrained fluid forms a thin spike growing from the rear stagnation point. If the vortex is initially oblate, irrotational fluid is entrained a t the rear stagnation point to the interior of the vortex.

58 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202336
202278
20217
20207
20196
201815