Alleviation of Aircraft Vortex Hazard Through Passive Aerodynamic Measures

Stuff, R.; Vollmers, H.

doi:10.2514/6.2003-1108

Cited by 5 publications

(4 citation statements)

References 5 publications

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“…Another form of wake vortex instability has also been suggested as a candidate for aircraft wake attenuation 13,14 . The Rayleigh-Ludwieg instability is a centrifugal form of instability that occurs naturally for two unbent, parallel vortex lines of opposite rotation.…”

Section: Introductionmentioning

confidence: 99%

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An Experimental Study of the Stability of a Four-Vortex System

Nelson

Babie

2005

23rd AIAA Applied Aerodynamics Conference

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An experiment is currently being conducted at the University of Notre Dame to investigate the interactions, and ultimately the instabilities, that persist in a four-vortex wake. A wake consisting of four trailing vortices was created in Notre Dame's atmospheric boundary layer wind tunnel. The advantage of this tunnel is the long test section, which permits the observation of wake interactions at distances up to thirty wake-spans downstream of the point of generation. The wake was created by four high aspect ratio wing models such that the circulation strength and the spacing between each vortex in the wake may be controlled. The principle aim of this study is to experimentally determine the optimal configurations, based on circulation strength and spacing, that are consistent with the rapid amplification of certain wake vortex instability modes. The primary method for evaluating the experimental facility has been flow visualization. Helium bubbles were introduced into the core region of individual vortices to visualize these wake structures. This paper presents some early results from the visualization of the four-vortex wake. These results suggest that the use of helium bubbles is a suitable method for visualizing wake vortices for the full length of the test section.

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Section: Introductionmentioning

confidence: 99%

“…There have been a number of recent studies that have investigated the instabilities that persist in a four-vortex wake, both experimentally 13,14,[21][22][23][24][25][26] and numerically 9,10,18,20 . These studies have also suggested the growth of the wake instability is a function of the circulation strengths of each of the vortex pairs.…”

Section: Introductionmentioning

confidence: 99%

An Experimental Study of the Stability of a Four-Vortex System

Nelson

Babie

2005

23rd AIAA Applied Aerodynamics Conference

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“…The Rayleigh -Ludwieg instability occurs naturally for two parallel vortices having an opposite sense of rotation [13][14] . The instability is caused when the destabilizing centripetal force is greater than the restoring pressure force within the vortex field.…”

Section: Introductionmentioning

confidence: 99%

The Trailing Vortex Wake Hazard: Beyond the Takeoff and Landing Corridors

Nelson

2004

AIAA Atmospheric Flight Mechanics Conference and Exhibit

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This paper focuses on issues related to the trailing vortex wake hazard beyond the takeoff and landing corridors. The operational procedures adopted by the FAA in the 1970s for avoiding wake turbulence encounters in the take-off and landing corridors have been very successful in providing commercial aviation with a high degree of safety. However, there is a growing body of evidence that encounters well beyond the immediate airport area could also prove to be hazardous. A review of commercial airline accidents for which a wake vortex encounter was considered to be a contributing factor in the accident are reviewed. Another problem that is addressed is wake encounters at cruise altitude. With the introduction of the regional jet transports into the commercial fleet we have created a very large disparity in the size of aircraft that can cruise at the same altitude. Furthermore there is evidence that wake encounters at cruise altitude do occur and should be investigated more extensively than has been done to date. In the current study the vortex induced loads created by wake vortices at cruise altitude are examined. The two cases that are presented include penetration perpendicular to the trailing vortex wake and penetration along the vortex core axis. The cross track penetration focuses on the structural loading while the along track penetration examines the potential roll excursion from the intended flight path.

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“…Other approaches include "turbulence injection" by means of splines, fins, vortex generators, spoilers, and Gurney flaps [86][87][88][89][90]. Stuff and Vollmers [91] induced the Raleigh Ludwieg instability to attenuate the wake vortices of transport aircraft but it works only with certain conditions for control surface vortex characteristics.…”

Section: Ground Modificationmentioning

confidence: 99%

Development and validation of new simulation method for wake-vortex decay in ground proximity with artificial enhancements

Paramasivam¹

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The aviation industry is undergoing a tremendous growth and is expected to continue in the decades ahead. One of the main factors affecting this growth is the airport capacity, which is limited by the frequency of landings and takeoffs. Aircrafts need to be separated since each aircraft is producing a pair of vortices in its wake that pose a danger to following aircraft. Even though a few concepts for reduced separation under certain conditions are being implemented at selected airports worldwide, it still persists to be a hurdle due to the limited knowledge of aircraft wake vortex decay. A clear understanding of wake-vortices and a precise prediction and avoidance system is required to establish an efficient operational method without jeopardising the safety of the aircrafts. The goal of this project is to study aircraft wake vortex decay and to reduce the impact of wake-vortices on the runway throughput. Hence, the wake-vortex dynamics at various atmospheric and wing span-loading conditions, in ground proximity is of primary focus for the current research. In this dissertation, the simulation software Jetcode, which was developed for combustion research at Stanford University, is adapted and validated for the wake-vortex research. Throughout the research, Lamb-Oseen vortex model is used to initialise the velocity fields of the shed wake-vortices. Large Eddy Simulations(LES) with dynamic Smagorinsky model is used to solve the unsteady, incompressible and viscous Navier-Stokes equation. The Temporal LES methodology is used for studying the atmospheric effects on wake-vortices. The effect of crosswind and turbulence intensity on the formation of secondary vortical structures in ground proximity are analysed in detail. The lateral transport of the primary vortex pair is investigated with two new parameters. Postprocessing codes to track the vortices and to determine the circulation of the vortices individually are developed. After performing the preliminary analysis on the wake vortex evolution, it is concluded that enhancing the secondary vortices interaction with the primary vortices result in an accelerated decay of the primary vortex pair. VII A new Prandtl Vorticity Distribution (PVD) method is introduced to initialise vortices, including those originating from the flaps, for any given lift distribution using Temporal LES methodology. This method is based on Prandtl Lifting-Line Theory and is effective in simulating the vortices shedding behind any type of aircraft with any high-lift configuration. The available measurements of B747 aircraft is considered for rest of the study. LIDAR measurements of landing 'Heavy' category aircrafts are used to validate the results of the new method. It has been found that the landing configuration of B747 results in a two pair wake-vortex system. The additional pair of vortices is due to the extension inboard flap. These inboard flap vortices greatly reduce the strength of the primary vortex pair. Using this method, the possibility of reducing the strength of the vortices by...

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Alleviation of Aircraft Vortex Hazard Through Passive Aerodynamic Measures

Cited by 5 publications

References 5 publications

An Experimental Study of the Stability of a Four-Vortex System

An Experimental Study of the Stability of a Four-Vortex System

The Trailing Vortex Wake Hazard: Beyond the Takeoff and Landing Corridors

Development and validation of new simulation method for wake-vortex decay in ground proximity with artificial enhancements

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