Wake Vortex Prediction Research Articles

Prediction of Aircraft Wake Vortices under Various Crosswind Velocities Based on Convolutional Neural Networks

In order to overcome the time-consuming computational drawback of using computational fluid dynamics (CFD) for the numerical simulation of aircraft wake vortex evolution under different crosswind velocities, this paper proposes a wake vortex prediction model based on a convolutional neural network (CNN) algorithm. The study focuses on the B737-800 aircraft, and employs CFD numerical simulations to obtain the evolutionary characteristics of wake vortex parameters under crosswind velocities ranging from 0 to 7 m/s. The wake vortex velocity and Q-criterion vorticity values are collected and partitioned into mutually exclusive training and testing datasets. A CNN model is constructed, and the training dataset is used to tune hyperparameters to minimize loss and achieve accurate predictions. After saving the trained model, the desired crosswind velocity value is input to obtain the predicted wake vortex velocity and Q-criterion vorticity values. The results indicate that the convolutional neural network model exhibits an average absolute percentage error of 1.5%, which is 2.3% lower than that of the fully connected neural network model. This suggests that convolutional neural networks can enhance the accuracy of wake vortex predictions, as demonstrated in this study. Compared to traditional CFD methods, the proposed model reduces the computation time by approximately 40 times, effectively improving computational efficiency and offering valuable insight for studies involving numerous numerical simulations, such as analyzing the safety separation between aircraft wake vortices during paired approach procedures.

Assessment of dynamic pairwise wake vortex separations for approach and landing at Vienna airport

The Wake Vortex Prediction System WSVS (WirbelSchleppenVorhersageSystem) has been developed to tactically increase airport capacity by employing dynamically adjusted aircraft separations for approach and landing without compromising safety. For this purpose, the WSVS considers the involved aircraft type pairing, the prevailing weather conditions, and the resulting wake vortex behavior. A Monte Carlo simulation study demonstrates that the WSVS is well adjusted to a reasonable level of safety. The simulation study evaluates the probability that wake vortices still linger within defined radii around the follower aircraft and compares this probability to measurement data collected at five major international airports. The potential of the WSVS to optimize aircraft separations is assessed by employing twelve months of traffic and weather prediction data collected at Vienna International Airport. Analyses of the separation reduction potential are established and compared to current regulations. Dependencies on prevailing headwind and crosswind conditions are discussed in terms of individual wake vortex behavior and statistical distributions of wake turbulence separations. The results indicate that substantial potential for safely reduced aircraft separations exists mainly under sufficiently strong crosswind conditions for any aircraft type combination requiring wake vortex separation minima.

The Influence of Grid Scale on the Tail Vortex Capture of Aircraft

The grid has appreciable impact on the simulation of the wake vortex. There is a big difference between the traditional aerodynamic estimation grid and the grid used for capture the main parameters of the trailing vortex in the far field. This paper compares the similarities and differences between these two kinds of grids. The main parameters of the coarse grid are quite different from those of the refined grid simulation in the far field. Sufficient quantity grids are required to simulate the flow field in the parameters of wake vortex prediction. Otherwise, it may draw the reverse conclusions with the physical truth.

Probabilistic Multimodel Ensemble Wake-Vortex Prediction Employing Bayesian Model Averaging

This paper investigates the capability of the multimodel ensemble approach to improve the deterministic forecast of wake-vortex behavior and to produce reliable probabilistic vortex habitation areas. Therefore, the deterministic two-phase wake vortex model D2P, the aircraft vortex spacing system prediction algorithm (APA) 3.2, APA 3.4, APA 3.8, and terminal area simulation system driven algorithms for wake prediction (TDP 2.1) wake-vortex models are exchanged within the framework of a NASA/DLR cooperation. These models are fused by the Bayesian model averaging approach, which is extended by temporally increasing uncertainties. In addition, combined confidence areas for the vertical and lateral vortex positions are derived from bivariate probability density distributions that are delivered by the ensemble and allow the computation of well-defined probability levels. For ensemble training and evaluation data collected at wake-vortex campaigns accomplished by NASA (at Memphis, Dallas, and Denver airports) and DLR (at Frankfurt, Munich, and Oberpfaffenhofen airports) are employed. Various training strategies are considered to obtain optimal prediction skill. The results demonstrate that a thoughtfully trained ensemble improves the deterministic prediction skill by up to 4.3% and is capable of predicting vortex habitation areas featuring reliable probability levels.

Analysis of potential wake vortex encounters at a major European airport

PurposeIn this study, 12 potential wake vortex encounters that were reported at a major European airport have been investigated. Because almost all encounters occurred in ground proximity, most pilots conducted a go-around. The primary purpose of this study is to discriminate between incidents caused by wake vortices or rather by effects like wind shear or turbulence. Detailed knowledge of real-world encounter scenarios and identification of worst-case conditions during the final approach constitute highly relevant background information to assess the standard scenario used for the definition of revised wake turbulence separations.Design/methodology/approachWake vortex predictions using the probabilistic two-phase wake vortex model (P2P) are used to investigate the incidents in detail by using data from the flight data recorder, meteorological instrumentation at the airport and numerical weather prediction.FindingsIn the best documented cases, the flight tracks through the vortices could be reconstructed in good agreement with wake vortex predictions and recorded aircraft reactions. Out of the eight plausible wake vortex encounters, five were characterized by weak crosswinds below 1.5 m/s combined with tailwinds. This meteorological situation appears favourable for encounters because, on the one hand, weak crosswinds may compensate the self-induced lateral propagation of the upwind vortex, such that it may hover over the runway directly in the flight path of the following aircraft. On the other hand, tailwinds limit the propagation of the so-called end effects caused by the breakdown of lift during touchdown.Practical implicationsThe installation of plate lines beyond the runway tails may improve safety by reducing the number of wake vortex encounters.Originality/valueThe conducted investigations provide high originality and value for both science and operational application.

Performance of Onboard Wake–Vortex Prediction Systems Employing Various Meteorological Data Sources

In this work the accuracy of wake–vortex predictions of DLR’s wake encounter avoidance and advisory system (WEAA) is analyzed by means of data gathered from a flight test campaign in April 2014. The system is based on airborne data exchange between aircraft and allows pilots to avoid potentially dangerous wake–vortex encounters. As the vortex evolution is strongly controlled by atmospheric parameters, the acquisition of meteorological data is crucial for WEAA. The accuracy of the wake–vortex predictions is investigated, employing first the current automatic dependent surveillance (ADS-B) standard, which is then extended by additional meteorological data transmitted via telemetry, or data from numerical weather predictions.

Dynamic separation minima coupled with wake vortex predictions in dependent runway configurations

Wake vortices are an issue affecting both capacity and safety of air traffic and therefore need to be dealt with by appropriate measures and procedures. Today, the only means to prevent wake vortex encounters is procedural separation which however is statical and in many cases conservative. The concept of dynamic separations using wake vortex predictions aims at optimising the separation between consecutive aircraft based on the knowledge of the actual position and strength of the wake vortices. A concept for approach procedures has been developed that involves dynamical calculation of minimum safe distance, adaption of follower aircraft speed and the corresponding approach types. The concept, its implementation and simulation test results will be presented and it will be discussed how it can be applied to contribute to an optimised use of available capacity while maintaining and improving the safety level.

Towards wake vortex safety and capacity increase: the integrated fusion approach and its demands on prediction models and detection sensors

Wake vortices and the prevention of wake vortex encounters are both an issue of safety and capacity in today’s air transportation system. Current wake vortex separations are safe but also very conservative and thus have an adverse effect on capacity of airports. This article deals with the concept of fused wake vortex prediction and detection with the objective to deliver wake vortex strength and position with a high level of accuracy and reliability. The collaboration approach aims at fusion of models and sensors available for forecast and detection of hazardous wake turbulence in order to improve the overall system performance using the complementary capabilities of the single components. Different methods of coupling models with measurements are introduced and resulting the aspect of requirements for the prediction model and measurement sensor is presented. The implementation of an error-state system is presented and compared to sole prediction and sole sensor results. The results indicate that the fusion approach delivers benefits like reduced uncertainty of prediction and increased availability of detection and thus has the ability to increase airport and air space capacity while maintaining or even improving current wake vortex safety.

Validation of time-lagged ensemble forecasts relevant for predicting aircraft wake vortices

Time-lagged ensemble (TLE) forecasts of the high-resolution model COSMO-FRA with an hourly update cycle and a lead time of 6 hours are validated against measurements of a Wind-Temperature Radar (WTR) for three cases representing different weather regimes, a frontal passage, a stormy situation and a high pressure system. Forecasts and measurements are available every 10 minutes. The present study focuses on parameters relevant for forecasting aircraft wake vortices, namely wind, virtual potential temperature and Turbulent Kinetic Energy (TKE) for altitudes below 1600 m. When compared with a reference run started once a day at 00 UTC with a lead time of 24 h a reduction of forecast error in the first two forecast hours is observed for all wind components. For wind speed at low levels around 400 m this reduction can be of order 1.7 ms-1 for the 1-hour forecast member and 0.9 ms-1 for the equally weighted ensemble mean depending on weather situation. TLE forecasts of virtual potential temperature show an improvement of close to 1 K except for the high pressure system while forecast errors of TKE are reduced below 900 m in all cases. Since no data assimilation is used, the improvements of the forecasts are the result of the hourly update cycle which benefits from more up-to-date initial- and boundary conditions provided by the driving COSMO-EU model. The results of this study may contribute to improve the quality of wake vortex predictions and encourage the assimilation of temporal high resolution wind data to further improve the very short range forecasts.

Wake vortex prediction and detection utilising advanced fusion filter technologies

AbstractAs a consequence of its aerodynamic lift, each aircraft is generating wake vortices that can become a serious hazard for the succeeding aircraft and in the worst case lead to loss of control. Separation standards were introduced to prevent dangerous wake encounters that have proven sufficiently safe but also very conservative, thus limiting airspace and airport capacity.The objective of contemporary wake vortex research is regaining capacity in favourable atmospheric conditions, at the same time preserving or even improving the current safety level. The wake vortex advisory systems developed for this purpose are nearing experimental implementation and all include a forecasting component and additional online detection sensors, with both elements having their benefits and limitations.The wake vortex research objectives at the Institute of Flight Guidance (IFF) of the Technische Universitaet Braunschweig focus on a close coupling approach between model predictions and sensor measurements. Using the complementary capabilities of each, the aim of improved performance of the overall system shall be reached.After giving a short overview on the wake vortex phenomenon and current approaches to wake vortex alerting and advisory systems, this paper will introduce the fusion concept. The benefits of this approach will be demonstrated by means of examples. An outlook on further development and envisaged advanced implementation concepts will be given.

The Wake Vortex Prediction and Monitoring System WSVBS Part II: Performance and ATC Integration at Frankfurt Airport

The performance and the ATC test integration of DLR’s wake vortex advisory system, WSVBS, for the dependent parallel runways 25L and 25R at Frankfurt Airport are described. WSVBS has components to forecast and monitor the local weather and to predict and monitor wake transport and decay along the glide paths. Integration with the DLR’s arrival manager AMAN has also been demonstrated. Every 10 minutes the WSVBS delivers minimum safe aircraft separation times for the next hour, which are translated into operational modes for runways 25L/R aiming at tactically improving capacity to reduce delays. During a performance test described herein the system was stable and the predicted minimum separation times were confirmed by measurements. Capacity-improving wake-vortex separation concepts of operation could have been used in 75% of the time and continuously applied for at least several tens of minutes. From fast-time simulations the (strategic) capacity gain for Frankfurt was estimated to be 3%, taking into account the real traffic mix and operational constraints.

The Wake Vortex Prediction and Monitoring System WSVBS Part I: Design

The design of the Wake Vortex Prediction and Monitoring System WSVBS is described with all its components and their interaction. The WSVBS was developed to tactically increase airport capacity for approach and landing on closely-spaced parallel runways. The WSVBS supports dynamic adjustment of aircraft wake vortex separations dependent on weather conditions and the resulting wake vortex behavior without compromising safety. Dedicated meteorological instrumentation and short-term numerical terminal weather prediction provide the input to the prediction of wake-vortex behavior and respective safety areas. The prediction tools employ a number of conservative aircraft parameter combinations that represent the medium and heavy aircraft weight categories. Safe aircraft separations correspond to times when the predicted safety areas associated with wake vortices generated by leading heavy aircraft cannot overlap the arrival flight corridor. A LIDAR monitors the correctness of WSVBS predictions in the most critical regions at low altitude.

Full-flight simulator study for wake vortex hazard area investigation

Simplified hazard areas (SHA) can help to overcome the wake vortex problem. Avoiding these zones allows safe and undisturbed flight operations. The definition of the hazard areas is based on the nominal required roll control power. The nominal limit for this value must be chosen carefully to ensure that outside the hazard area all wake vortex effects are noncritical. For the determination of such a limit offline simulations and full flight simulator studies were conducted. For a given roll control limit the hazard area dimensions are established with the “simplified hazard area prediction” method (SHAPe). Parameterization of the input parameters makes this method universally applicable to different aircraft types. SHAPe represents an essential element of the wake vortex prediction and observation system within the DLR project Wirbelschleppe II, for the generation of safe dynamic wake vortex separations.

An assessment of the 2D vortex method in aircraft wake simulation

Abstract Recent interest in aircraft vortex wakes has highlighted the need to identify appropriate algorithms for their simulation. The problem is not well-suited to grid-based techniques, due to the large domain and the need to avoid introducing artificial viscosity. A promising alternative is offered by Lagrangian formulations. This work aims to assess the usefulness of one such approach - the 2D vortex method -via comparison with experimental results. One in-house and two external (from DLR and ONERA) data sets are used. The results show generally good agreement in vortex locations and size, with the calculation performing best when initialised downstream of the strongly-three-dimensional trailing edge region. The neglect of viscosity can lead to some asymmetry in the vortex cores, but, even here, excellent agreement can be obtained when the field is integrated to give circulation (as a function of radius). The 2D vortex method is thus an accurate and efficient tool for wake vortex prediction.