Aircraft Wake Recognition and Strength Classification Based on Deep Learning

In order to study the wake vortices generated by landing aircrafts, we conducted an experiment on the airfield of Tolmachevo Airport in 2018, which involved the Stream Line lidar, AMK-03 sonic anemometer and MTP-5 temperature profiler. The experiment determined the limits of applicability of the radial velocity method used to obtain estimates of the parameters of wake vortices from lidar measurements, depending on the type of aircraft and the intensity of wind turbulence. An analysis of the experimental results made it possible to identify a number of features of the spatial dynamics and evolution of aircraft wake vortices during different states of the surface layer of the atmosphere. In particular, it was found that in the case of low average lateral wind speed and moderate wind turbulence, the lifetime of the vortex formed behind the landing aircraft MD-11F can reach almost 4 minutes.

In order to study the wake vortices of landing aircraft, we carried out an experiment on the airfield of Tolmachevo Airport in 2018 using Stream Line lidar, an AMK-03 sonic anemometer, and an MTP-5 temperature profiler. The limits of applicability of the method of radial velocity in estimation of wake vortex parameters from lidar measurements were determined for different aircraft types and wind turbulence strength. The analysis of the experimental results makes it possible to identify features of the spatial dynamics and evolution of aircraft wake vortices under different states of the surface air layer. In particular, we found that the lifetime of a vortex generated behind a large MD-11F aircraft on landing can reach 4 min in the case of low average crosswind speed and moderate wind turbulence.

This paper presents three-dimensional large eddy simulations (LES) and two-dimensional direct numerical simulation (DNS) of wake vortices of an aircraft in a realistic atmospheric boundary layer (ABL). These calculations are performed in order to parametrize an operational model aiming at managing the separations between aircraft at take-off and landing. The computation considered here is taken from twelve selected cases corresponding to trials made at Idaho Falls sponsored by the Federal Aviation Administration (FAA) in 1990. After computing the evolution of a convective atmospheric boundary layer with a non-hydrostatic meteorological model, the evolution of the wake vortices (with their characteristics measured during the experiments) is computed. The threedimensional behavior of the wake vortices as well as the effects of the atmospheric parameters are shown. The results of the simulations are compared to experimental data.

Enhancement of wake vortex decay by air blowing from the ground

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.

NASA has an on-going field experiment at Memphis International Airport to measure wake turbulence generated by aircraft in the near-ground effect region. This new data will be used in the validation and improvement of fast-time numerical wake vortex models, and provide an important data set to be used in the further development of probabilistic wake vortex estimation algorithms. An important component of this field program is to obtain high-quality estimates of important weather conditions in, or near, the region where the wake vortices are generated and tracked, and at a frequency such that the scales of variability important to the evolution of wake vortices is observed. In this paper we will describe the intercomparisons of the estimates derived from multiple sensors for the important weather parameters of atmospheric turbulence and wind speed and direction. Using the results of this intercomparison, we will provide some guidance on what uncertainties may be applicable and useful when utilizing different sources for the estimation of the meteorological condition in probabilistic fast-time wake vortex simulations.

Aircraft interacts with the ground through landing gear system, while taxiing down the runway.Under rain or snow conditions, water film splashed by aircraft tires during taxiing on water-covered runways adheres to the landing gear, leading to ice accretion under low-temperature conditions, which may directly compromise aircraft takeoff and landing safety. Due to the substantial resource consumption required for experimental investigation of this problem, numerical simulation was employed to model the phenomenon.The water film icing process can be divided into two main stages: the formation of water film on the landing gear caused by tire spray, and the subsequent icing and heat transfer process of the splashed water film on the landing gear, this study conservatively simplifies the tire spray phenomenon as a typical liquid-solid two-phase coupling problem. A Finite Volume Model simulating water accumulation dynamics on landing gear tires was developed in Fluent software, based on extreme runway water accumulation conditions and extreme navigation weather scenarios during takeoff of a domestic civil aircraft model. The model incorporates coupled tire-water film-landing gear interactions. The VOF (Volume of Fluid) model and mesh motion are employed to calculate the water film thickness on the landing gear. A conservative thermodynamic equilibrium equation is then constructed based on boundary conditions to estimate the ice accretion thickness. The article analyzed the influence of external factors (aerodynamic drag, gravitational force, etc.) on water film thickness. The calculation results indicate that a conservative estimation of ice accretion derived from water film thickness does not compromise takeoff and landing safety, thereby validating that under rainy or snowy weather conditions with water accumulation on the runway, the conservative maximum icing thickness resulting from wheel spray water and landing gear water accumulation during aircraft taxiing will not exceed a level sufficient to pose a threat to aircraft takeoff and landing safety.

Wake vortex safety analysis and control for unmanned aircraft systems (UAS) operating alongside commercial aircraft in the terminal zones are critical aspects in the integration of UAS into the National Airspace System (NAS), particularly in terminal airspace. We address an approach that integrates reduced-order models of wake generation, evolution, interaction and its control incorporating both theoretical and high-fidelity predictions. Our previous study [1] estimated UAS responses in terms of the roll control ratios (RCR) developed by the follower aircraft depending on their position and orientation relative to the wake shed by the leader aircraft, as well as the duration of the wake-UAS interaction. The current paper complements and expands the previous study to describe a predictive, robust feedback-loop flight control model that is applicable to various classes of UAVs in unsteady flight-path scenarios including control of wake response. The control design presented in this paper extends previous research results by first demonstrating asymptotic (zero steady-state error) altitude regulation control in the presence of unmodeled vertical wind gust disturbances. To address the practical considerations involved in small UAV applications with limited computational resources, the proposed control method is designed with a computationally simplistic structure, without the requirement of complex calculations or function approximators in the control loop. Proof of the theoretical result is summarized, and detailed numerical simulation results are provided, which demonstrate the capability of the proposed nonlinear control method to asymptotically reject wind gust disturbances and parameter variations in the state space model. Simulation comparisons with a standard linear control method are provided for completeness.

Strong convection is the important weather phenomenon impacting the flight safety, always causes sudden changes of meteorological elements. AMDAR data is of high resolution on spatial and temporal, which can provide vital information for the short-term forecast of strong convection weather in the airport terminal area. This paper extracts the three-dimensional vertical wind profiles and temperature profiles, and produces the wind shear warning analysis diagram in the horizontal and vertical direction. The case studied in this paper is a strong convection at April 2011 in Guangdong Province, AMDAR data, together with multi-source information such as radar, satellite and air sounding is analyzed. The study has found that with high resolution spatial and temporal AMDAR data, wind and temperature disturbance information could reveal the motion of wind shear and turbulence in the airport, so that the unique observational basis for protecting the aircraft's take-off and landing safety is provided.

This paper investigates alternative moment generation mechanisms for aircraft as fuelsaving techniques in formation ight. Aircraft ight generates wake vortices that induce a nonuniform wind distribution in the wake of the aircraft. A follower aircraft, ying in the wake of the leader aircraft, can experience induced wind components and gradients with various magnitudes and directions, depending on the location within the induced nonuniform wind eld. It has been demonstrated that there is a sweet spot within the wake of the leader aircraft where the follower aircraft experiences upwash, which leads to drag reduction. When an aircraft ying in formation ight is at the sweet spot, the aircraft experiences lower drag but at the same time experiences induced aerodynamic moments. The de ections of control e ectors required for trimming the aircraft under the e ect of these moments induce additional drag, which reduce the bene ts of fuel e ciency. This report investigates two di erent mechanisms of moment generation for alleviating the drag induced by the de ection of the control e ectors: (1) internal fuel transfer among fuel tanks and (2) di erential thrust. It was seen that an elimination of the control e ector de ections led to a reduction in the thrust required and thus savings in fuel. Internal fuel transfer, in the con guration studied, was seen to reduce the aileron de ection of the follower by generating a rolling moment, and di erential thrusting reduced the rudder de ection by the generation of a yawing moment. Furthermore, the combination of the two techniques provided the highest fuel savings of 11 percent by reducing the need for the aileron and rudder de ections. The results of this analysis will allow for further studies ultimately leading to the development of a fuel-saving method of ight with various applications.

Control of trailing vortex wakes is an important challenges for both military and civilian applications. This paper summarizes an assessment of the feasibility of mitigating adverse vortex wake effects using control surfaces actuated via Shape Memory Alloy (SMA) technology. The assessment involved a combined computational/design analysis that identified methods for introducing small secondary vortices to promote the deintensification of vortex wakes of submarines and aircraft. Computational analyses of wake breakup using this `vortex leveraging' strategy were undertaken, and showed dramatic increases in the dissipation rate of concentrated vortex wakes. This paper briefly summarizes these results and describes the preliminary design of actuation mechanisms for the deflectable surfaces that effect the required time-varying wake perturbations. These surfaces, which build on the high-force, high- deflection capabilities of SMA materials, are shown to be well suited for the very low frequency actuation requirements of the wake deintensification mission. The paper outlines the assessment of device performance capabilities and describes the sizing studies undertaken for full-scale Vortex Leveraging Tabs (VLTs) designed for use in hydrodynamic and aerodynamic applications. Results obtained to date indicate that the proposed VLTs can accelerate wake breakup by over a factor of three and can be implemented using deflectable surfaces actuated using SMAs.

specifically, wind shear, defined as the vertical change of the horizontal wind, are less well understood. In this study, we used laboratory experiments and numerical simulations to examine the effects of shear on the evolution of wake vortices. It is found that the second derivative of the crosswind profile is the important parameter in determining the vertical position of the vortices and the angle of tilt of a line joining the vortex cores. A concave shear profile tilts the vortices in one direction while a convex profile tilts the vortices in the other direction. The stronger the shear gradient, the larger the vortex tilt, and the slower the vertical migration speed of the vortex pair through the shear gradient, the larger the vortex tilt. The tilt of the vortex cores begins when the vortex cell first enters the region where the shear gradient is non-zero, and the tilt stops changing when the vortex cell leaves the region where the shear gradient is non-zero. Thus, the shear gradient affects the entire vortex cell, not just the vortex cores. The numerical simulations predict quite well the observed vertical descent and the tilt of the vortex cores observed in the laboratory experiments.

This study numerically investigates the influence of square-wave inlet velocity pulsations on flow structure and heat transfer around a transverse circular cylinder, with particular emphasis on wall condensation behavior. The evolution of wake vortices and the distribution of the convective heat transfer coefficient on the cylinder surface are analyzed under both single-phase and two-phase flow conditions over a range of pulsation frequencies. The results indicate that inlet pulsations significantly modify the wake dynamics, leading to reduced vortex size and enhanced momentum and turbulence dissipation in single-phase flow, which in turn improves convective heat transfer downstream of the separation point. Under two-phase condensation conditions, similar wake modifications are observed, while additional small-scale vortical structures are generated within the condensate film due to interfacial shear, further enhancing local heat transfer. Overall, the findings demonstrate that appropriately tuned inlet pulsations can effectively enhance heat transfer performance for both single-phase and condensing flows around a circular cylinder.

: An experimental study of the tip vortex behind a NACA 0015 rectangular wing of aspect ratio 4 was carried out to understand the structure and evolution of the vortex in the near-wake region. The results of these experimental studies are presented in this report. These measurements were made nonintrusively using three-component laser-Doppler velocimetry (LDV). The experiments were carried out at a Reynolds number of about 180,000 in a low- speed wind tunnel. Two cases were studied, namely, (1) stationary wing and (2) wing oscillating in pitch sinusoidally about its quarter-chord axis. The flow properties measured were the three components of the instantaneous velocity. These data were processed to obtain time-mean and phase-locked flow properties such as velocity, vorticity and turbulence. The data were obtained at several locations at 0.15 - 3.0 chord lengths downstream from the trailing edge. The typical distributions of mean velocity, vorticity, circulation and turbulent intensity in the near wake are presented and discussed for the stationary wing. In the case of the oscillating wing, the phase-locked velocity, vorticity and turbulence data show details of the evolution of the unsteady tip vortex downstream from the trailing edge. The results also show that the flow is strongly non-quasi-steady at the oscillation frequency studied. The results are fully archived on tape and are available to any interested reader. These can be used as database in the development of wake models for the finite wing, and in studies of three-dimensional wing aerodynamics.

A new parametric wake vortex transport and decay model is proposed that predicts probabilistic wake vortex behavior as a function of aircraft and environmental parameters in real time. The probabilistic two-phase wake vortex decay model (P2P) accounts for the effects of wind, turbulence, stable stratie cation, and ground proximity. The model equations are derived from the analytical solution of the spatiotemporal circulation evolution of the decaying potential vortex and are adapted to wake vortex behavior as observed in large-eddy simulations. Vortex decay progresses in two phases, a diffusion phase followed by rapid decay. Vortex descent is a nonlinear function of vortex strength. Probabilistic components account for deviations from deterministic vortex behavior inherently caused by the stochastic nature of turbulence, vortex instabilities, and deformations, as well as uncertainties and e uctuations that arise from environmental and aircraft parameters. The output of P2P consists of cone dence intervals for vortex position and strength. To assign a dee ned degree of probability to the predictions reliably, the model design allows for the continuous adjustment of decay parameters and uncertainty allowances, based on a growing amount of data. The application of a deterministic version of P2P to the Memphis wake vortex database yields favorable agreement with measurements.