Improved Understanding of En Route Wake-Vortex Encounters

Hoogstraten, Mike; Visser, H.G.; Hart, Dennis L.; Treve, Vincent; Rooseleer, Frédéric

doi:10.2514/1.c032858

Cited by 10 publications

(12 citation statements)

References 5 publications

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“…Second, the present study demonstrated that, at least for two aircraft configurations, the descent speed and the final vertical displacement of the vortices in a FF scenario are smaller than in the classical SA scenario. Hence, the probability of interferences across different flight levels (the main reason for in-cruise wake vortex incidents (70)(71)(72) ) is likely to be reduced. Moreover, the experienced roll moments behind an AC formation wake may differ from those behind a single aircraft wake and may impact the severity of encounters.…”

Section: Discussionmentioning

confidence: 99%

Far field wake vortex evolution of two aircraft formation flight and implications on young contrails

Unterstraßer

Stephan

2020

Aeronaut. j.

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Large-eddy simulations (LES) have been employed to investigate the far-field four-vortex wake vortex evolution over 10min behind an aircraft formation. In formation flight scenarios, the wake vortex behaviour was found to be much more complex, chaotic and also diverse than in the classical single aircraft case, depending very sensitively on the formation geometry, i.e. the lateral and vertical offset of the two involved aircraft. Even though the case-by-case variability of the wake vortex behaviour across the various formation flight scenarios is large, the final plume dimensions after vortex dissolution are in general substantially different from those of single aircraft scenarios. The plumes are around 170 to 250m deep and 400m to 680m broad, whereas a single A350/B777 aircraft would produce a 480m deep and 330m broad plume. Formation flight plumes are thus not as deep, yet they are broader, as the vortices do not only propagate vertically but also in span-wise direction. Two different LES models have been employed independently and show consistent results suggesting the robustness of the findings. Notably, $CO_{2}$ emissions are only one contribution to the aviation climate impact among several others like contrails and emission of water vapour and nitrogen oxides, which would be all affected by the implementation of formation flight. Thus, we also highlight the differences in ice microphysical and geometrical properties of young formation flight contrails relative to the classical single aircraft case.

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Section: Discussionmentioning

confidence: 99%

Far field wake vortex evolution of two aircraft formation flight and implications on young contrails

Unterstraßer

Stephan

2020

Aeronaut. j.

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“…where θ is the potential temperature, ω is the potential temperature lapse rate, and h is the altitude. Higher N is associated with higher stability and buoyancy force acting on the WV, which causes faster WV decay rate [12]. N is generally higher in the stratosphere than the troposphere.…”

Section: Modeling Of Wake Vortexmentioning

confidence: 99%

“…The decay and descent rates depend mainly on the wind shear, atmospheric turbulence, and thermal stratification [10,22,23]. The latter is the atmospheric condition that causes the greatest effect on the WV evolution, and is frequently described by the Brunt-Väisälä frequency N [12,24]:…”

Section: Modeling Of Wake Vortexmentioning

confidence: 99%

“…Although the current rate of reported incidents related to WVE at en-route altitudes may be low, the problem of WVE en-route has received increasing attention in the last decade. This is due to the fact that WVE have become more frequent [1] and they will probably increase in the near future due to the expected evolution of the main factors contributing to WVE risk en-route (the characteristics of the generator and follower aircraft, encounter geometry, and tropopause altitude [12]) and other issues [13]: a growing amount of traffic in a very limited airspace (optimal cruise altitudes for the majority of jet aircraft lie in a rather thin layer around the tropopause); an increasing disparity in the size of…”

Section: Introductionmentioning

confidence: 99%

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Sensitivity Analysis of Maximum Circulation of Wake Vortex Encountered by En-Route Aircraft

2021

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Wake vortex encounters (WVE) can pose significant hazard for en-route aircraft. We studied the sensitivity of wake vortex (WV) circulation and decay to aircraft mass, altitude, velocity, density, time of catastrophic wake demise event, eddy dissipation rate, wing span, span-wise load factor, and WV core radius. Then, a tool was developed to compute circulations of WV generated/encountered by aircraft en-route, while disregarding unrealistic operational conditions. A comprehensive study is presented for most aircraft in the Base of Aircraft Data version 4.1 for different masses, altitudes, speeds, and separation values between generator and follower aircraft. The maximum WV circulation corresponds to A380-861 as generator: 864 and 840 m2/s at horizontal separation of 3 and 5 NM, respectively. In cruise environment, these WV may descend 1000 ft in 2.6 min and 2000 ft in 6.2 min, while retaining 74% and 49% of their initial strength, respectively. The maximum circulation of WV encountered by aircraft at horizontal separation of 3 NM from an A380-861 is 593, 726, and 745 m2/s, at FL200, FL300, and FL395, respectively. At 5 NM, the circulations decrease down to 578, 708, and 726 m2/s. Our results allow reducing WVE simulations only to critical scenarios, and thus perform more efficient test programs for computing aircraft upsets en-route.

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“…The simulation assumes constant values for the eddy dissipation rate (EDR), intrinsic values of Brunt-Va¨isa¨la¨frequency, and constant crosswind speed. Typical values of the Brunt-Va¨isa¨la¨frequency measured in the field range between 0.01 and 0.015 radians per second (s -1 ) (5), where greater values indicate larger buoyancy force is acting on the wake and result in an increased wake decay rate (11).…”

Section: Maximum Wake Circulation Capacitymentioning

confidence: 99%

Simulation of Runway Operations with Application of Dynamic Wake Separations to Study Runway Limitations

Roa

Trani

et al. 2020

Transportation Research Record

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This paper presents an evaluation of runway operations at Chicago O’Hare International Airport to estimate the impact of proposed wake vortex separation including Recategorization Phase II and III dynamic separations. The evaluation uses a Monte Carlo simulation model that considers arrival and departure operations. The simulation accounts for static and dynamic wake vortex separations, aircraft fleet mix, runway occupancy times, aircraft approach speeds, aircraft wake circulation capacity, environmental conditions, and operational error buffers. Airport data considered for this analysis are based on Airport Surface Detection Equipment Model X records from Chicago O’Hare International Airport from January to November 2016. Dynamic wake separations are tailored to each unique set of conditions by using environmental and aircraft performance parameters as input and allowing aircraft to be exposed to the same wake vortex strength as in Recategorization Phase II (RECAT II). The analysis shows that further reductions beyond RECAT II for aircraft pairs separated by 2 nautical miles or less is not operationally feasible. These wake separations already result in little to no wake dependency. When this is the case, the challenges in wake separation are to meet runway occupancy times and to make sure aircraft separations allow for human operational variations without resulting in aircraft turnarounds or double-aircraft-occupancy runway violations.

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Improved Understanding of En Route Wake-Vortex Encounters

Cited by 10 publications

References 5 publications

Far field wake vortex evolution of two aircraft formation flight and implications on young contrails

Far field wake vortex evolution of two aircraft formation flight and implications on young contrails

Sensitivity Analysis of Maximum Circulation of Wake Vortex Encountered by En-Route Aircraft

Simulation of Runway Operations with Application of Dynamic Wake Separations to Study Runway Limitations

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