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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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Patent
16 Aug 1996
TL;DR: In this article, a half-plow vortex generator is used to generate a primary corotating vortex of sufficient strength to interact with and accelerate the dissipation of the tip vortex generated by the same main rotor blade.
Abstract: In one embodiment for a helicopter main rotor assembly, a half-plow vortex generator is mounted in combination with the upper aerodynamic surface of each main rotor blade and is operative to generate a primary corotating vortex of sufficient strength to interact with and accelerate the dissipation of the tip vortex generated by the same main rotor blade, thereby reducing blade-vortex interaction noise radiating from the helicopter main rotor assembly. The half-plow vortex generator has a right triangular planform configuration defined by a length, a width, and an apex angle. The three-dimensional configuration of the vortex generator is further defined by an apex height. The apex height is the primary determinant of the strength of the generated primary corotating vortex and is defined in terms of the thickness of the main rotor blade at the local chord where the vortex generator is mounted. The apex height may be approximately equal to the local thickness, but preferably has a magnitude within the range of about one-eighth to about three-quarters of the local thickness. The length, width, and apex angle are secondary determinants of the strength of the primary corotating vortex generated by the half-plow vortex generator. The length and width of the vortex generator are defined in terms of the tip chord length of the main rotor blade, the length preferably having a magnitude within the range of about one-fourth to one-half of the tip chord length and the width preferably having a value of about one-third of the length of the vortex generator. The apex angle preferably has a value within the range of about twenty to about thirty degrees. The mounting site for the half-plow vortex generator is defined in terms of the length of the local and tip chords, respectively. The vortex generator is mounted inboardly from the tip of the main rotor or blade a spanwise distance having a magnitude preferably within the range of about one-half of to about equal to the tip chord length in substantial alignment with the local chord. The apex of the vortex generator is mounted inwardly from the leading edge of the main rotor blade by a chordal distance having a magnitude of about one-quarter the local chord length.

44 citations

Patent
22 Dec 2011
TL;DR: In this article, a three-dimensional crenulated airfoil configuration is proposed to facilitate desensitization of an air-foil unsteady pressure response to at least one impinging upstream generated wake or vortex by decorrelating spatially and temporally.
Abstract: An airfoil and method of fabricating an airfoil including a first and a second side coupled together at a leading and a trailing edge and extending there between. The airfoil includes a plurality of first chord sections having a first chord length and extending outward from one of the first side or second side of the airfoil at the leading edge and a plurality of second chord sections having a second chord length and extending outward from the one of the first side or the second side of the airfoil at the leading edge. The leading edge including spaced-apart wave-shaped projections defining a waveform. The configuration defining a three-dimensional crenulated airfoil configured to facilitate desensitization of an airfoil unsteady pressure response to at least one impinging upstream generated wake or vortex by decorrelating spatially and temporally and reducing in amplitude an unsteady pressure caused by interaction of the airfoil with the upstream generated wake or vortex.

44 citations

01 Mar 1992
TL;DR: In this article, the authors investigated the effect of various forms of active control on the unsteady and time-mean flow structure of leading edge vortices on a delta wing.
Abstract: The unsteady flow structure of leading-edge vortices on a delta wing has been investigated using new types of experimental techniques, in order to provide insight into the consequences of various forms of active control. These investigations involve global control of the entire wing and local control applied at crucial locations on or adjacent to the wing. Transient control having long and short time-scales, relative to the convective time-scale C/U(sub infinity), allows substantial modification of the unsteady and time-mean flow structure. Global control at long time-scale involves pitching the wing at rates an order of magnitude lower than the convective time-scale C/U(sub infinity), but at large amplitudes. The functional form of the pitching maneuver exerts a predominant influence on the trajectory of the feeding sheet, the instantaneous vorticity distribution, and the instantaneous location of vortex breakdown. Global control at short time-scales of the order of the inherent frequency of the shear layer separating from the leading-edge and the natural frequency of vortex breakdown shows that 'resonant' response of the excited shear layer-vortex breakdown system is attainable. The spectral content of the induced disturbance is preserved not only across the entire core of the vortex, but also along the axis of the vortex into the region of vortex breakdown. This unsteady modification results in time-mean alteration of the axial and swirl velocity fields and the location of vortex breakdown. Localized control at long and short time-scales involves application of various transient forms of suction and blowing using small probes upstream and downstream of the location of vortex breakdown, as well as distributed suction and blowing along the leading-edge of the wing applied in a direction tangential to the feeding sheet. These local control techniques can result in substantial alteration of the location of vortex breakdown; in some cases, it is possible to accomplish this without net mass addition to the flow field.

44 citations

Journal ArticleDOI
TL;DR: In this article, high-frequency limit-cycle oscillations of an airfoil at low Reynolds number were studied numerically, where the aerodynamic model used in the aeroelastic framework is a potential-flow-based discrete-vortex method, augmented with intermittent leading-edge vortex shedding based on a leading edge suction parameter reaching a critical value.

44 citations

Journal ArticleDOI
TL;DR: In this article, the vortex ring was observed to pinch-off, or become disconnected, from the trailing plume, at non-dimensional times, or formation numbers, between 4.4 and 4.9.
Abstract: The vortex ring formation process of a starting buoyant plume was studied experimentally using digital particle image thermometry and velocimetry (DPITV). The vortex ring was observed to pinch-off, or become disconnected, from the trailing plume. Pinch-off occurred at non-dimensional times, or formation numbers, between 4.4 and 4.9. The observed pinch-off process is consistent with an explanation based upon the Kelvin–Benjamin variational principle. This is analogous to the pinch-off of a vortex ring generated using a piston–cylinder apparatus, suggesting that pinch-off is a general component of the vortex ring formation process for various generation mechanisms.

44 citations


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