Prediction of Dynamic Pairwise Wake Vortex Separations for Approach and Landing

Flow Turbulence Combust

Tchipev

Stephan

2016

Self Cite

Wall-resolved large eddy simulations are employed to investigate the behaviour of wake vortices and single vortices in ground proximity at a variety of wind conditions. The six considered strengths of wind, ranging between 0.5 and 4 times the initial wake vortex descent speed, w 0 , include practically and theoretically significant wind speeds. A crosswind of 0.5 w 0 may lead to windward stall posing a potential hazard to subsequently landing aircraft, whereas theoretical considerations predict that at 4 w 0 the rebound of the luff vortex is completely suppressed. The same range of wind speeds is also used to investigate the effects of headwind and diagonal wind in order to discriminate between effects of environmental turbulence increasing with wind speed and the direction of the wind shear. The study has been complemented by a number of single vortex computations in order to differentiate between effects related to the mutual interaction of the vortex pair and the individual vortices with the turbulent boundary layer flow. It is shown that vortex ascent, descent, rebound and decay characteristics are controlled by (i) the interaction of the vortices with secondary vorticity detaching from the ground, (ii) the redistribution of vorticity of the boundary layer which is altering the path of the primary vortices by mutual velocity induction, and (iii) the interaction of the vortices with the environmental turbulence.

Section: Introductionmentioning

confidence: 98%

Wind Impact on Single Vortices and Counterrotating Vortex Pairs in Ground Proximity

Flow Turbulence Combust

Tchipev

Stephan

2016

Self Cite

“…Long-term lidar measurements of wake vortices at Charles de Gaulle airport indicate that in 3% of the cases the vortices are at least as close as 25 m to following landing aircraft within one gate close to the threshold 10 . An analysis of DLR's wake vortex advisory system WSVBS demonstrates that in 57% -70% of landings wake vortex behavior in ground proximity impedes reduced separations 11 . Moreover, the possibilities of the pilot to recover from a vortex encounter are limited by the low flight altitude.…”

Section: Introductionmentioning

confidence: 99%

Wake Vortex Evolution During Approach and Landing With and Without Plate Lines

52nd Aerospace Sciences Meeting

Stephan

Körner

et al. 2014

Data from numerical simulations and two field measurement campaigns are used to investigate aircraft wake vortex evolution during final approach and landing with and without a plate line. A new hybrid simulation method is employed to capture wake vortex evolution from early roll-up to final decay in ground proximity. Vortex decay is driven by the turbulence of the aircraft wake itself, the interaction of the wake vortices with the ground, the so-called end effects triggered by the sudden loss of lift during touchdown, and it is artificially augmented by a plate line installed a few hundred meters from the runway threshold. The field experiments WakeMUC at Munich airport and WakeOP at special airport Oberpfaffenhofen corroborate and complement the findings of the simulations. The end effects together with an acceleration of the decay in close ground proximity significantly accelerate vortex decay nearby the runway. In view of the fact that the probability to encounter wake vortices is distinctly increased in ground effect, the described mechanisms ensure the required safety of air traffic operations. Experiments and simulations demonstrate that plate lines appreciably accelerate wake vortex decay and interfere favorably with end effects. This way safety can be further increased during the flight phase with most reported encounters.

“…In the first run, the Maximum Landing Weight (MLW) is employed for maximum circulation. In the second run, the Operational Empty Weight (OEW) plus the fuel weight for one hour of flight plus the weight of 10% of the maximum amount of passengers as input is applied for the minimum circulation [161]. To model the advection of the vortices caused by head-or tailwind properly, the whole gate is transported according to the windspeed.…”

Section: Concept Of Operations Implementation Into the Wsvbsmentioning

confidence: 99%

“…In a next step, the elliptical approach corridor (1 or 2σ) is added. It is derived from studies of the arrival flight tracks at the airports of St. Louis, Atlanta and Chicago below a distance of 3.3 NM and at larger distances from the flight path adherence statistics (FLIP) [161]. The corridor dimensions decrease when approaching the runway [161].…”

Section: Concept Of Operations Implementation Into the Wsvbsmentioning

confidence: 99%

Multi-model ensemble wake vortex prediction

Körner

Aircraft Eng & Aerospace Tech

2016

Self Cite

Tag der mündlichen Prüfung: 25.07.2017 Diese Dissertation ist auf den Internetseiten der Universitätsbibliothek online verfügbar. Für meinen Großvater. v Eidesstattliche Erklärung Ich versichere hiermit an Eides Statt, dass ich die vorliegende Dissertation mit dem Titel "Multi-Model Ensemble Wake Vortex Prediction" selbstständig und ohne unzulässige fremde Hilfe erbracht habe. Ich habe keine anderen als die angegebenen Quellen und Hilfsmittel benutzt. Für den Fall, dass die Arbeit zusätzlich auf einem Datenträger eingereicht wird, erkläre ich, dass die schriftliche und die elektronische Form vollständigübereinstimmen. Die Arbeit hat in gleicher oderähnlicher Form noch keiner Prüfungsbehörde vorgelegen. Zudem versichere ich Eides statt, dass ich kein erfolgloses Promotionsverfahren bzw. Promotionsstudium zum Dr.-Ing/ Dr.rer.nat. durchgeführt habe. AbstractAs a response to lift, a complex flow pattern is shed from the wings of an aircraft that evolves into a pair of counter-rotating vortices. Their behavior is strongly influenced by the atmosphere and further underlies a complex interaction with the ground. Due to the rolling momentum that the vortices may induce and the forces that they can exert they pose a potential hazard to following air traffic, especially along the glide path and in ground proximity. To avoid dangerous incidents, separation regulations based on aircraft mass exist that is currently under revision in the context of RECAT. However, air traffic is expected to further increase in the future, making wake vortex encounters more likely. For this reason fast-time wake vortex models have been developed in the past that predict the vortex position and strength dependent on the aircraft parameters and the ambient conditions in order to avoid dangerous situations. Furthermore, they may reduce flight delays at congested airports as they allow adapting overly conservative separations tactically under certain conditions. However, forecasts include uncertainties that originate from inaccurate and highly variable initial and ambient conditions as well as from inadequate understanding and simplification of the underlying physics. As a consequence, deterministic forecasts are to be complemented by probabilistic envelopes.In the field of meteorology such envelopes are frequently computed by combining the forecasts of multiple independent models to quantify the model uncertainty. This approach, also known as Multi-Model Ensemble (MME), has not only shown to increase the reliability of the probabilistic forecast but also to enhance its deterministic skill. For this reason the capability of the MME approach to improve both deterministic and probabilistic wake vortex forecasts is assessed and existing approaches are further developed in this thesis. Three of the ensemble members have been provided in the frame of a NASA-DLR cooperation. The employed models comprise APA 3.2, APA 3.4 and TDP 2.1 (NASA) and are combined with the DLR model D2P. Several MME approaches are examined, comprising the Direct Ensemble Average...