| 1. |
- Thoma, Evangelia Maria, 1996, et al.
(författare)
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Assessment of an Open-Source Aircraft Noise Prediction Model Using Approach Phase Measurements
- 2024
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Ingår i: Journal of Aircraft. - 0021-8669 .- 1533-3868. ; 61:3, s. 745-760
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Tidskriftsartikel (refereegranskat)abstract
- An open-source simulation model for aircraft noise prediction is presented and validated using backpropagated noise measurements for a state-of-the-art engine and aircraft. The validation is focused on approach procedures and was performed using ground-based noise measurements that were taken at 17 recording stations for a total of 18 consecutive flights carried out during the morning of 8 April 2021. The flights were performed using two A321neo aircraft with LEAP-1A engines. It is demonstrated that the presented noise model provides a satisfactory estimation of the source noise for varying approach configurations and flight conditions. Configurations using a greater number of high-lift devices are particularly well predicted in the mid- and high-frequency regions, whereas the lower configuration settings show greater spectral deviations, which are partly attributed to measurement uncertainties caused by the increased aircraft–microphone distance. The model can predict the overall mean total sound intensity level within a 2 dB accuracy for all configurations, while the average predicted level at each microphone differs by less than 3 dB from the measurement average, for all cases except one. Variation in aircraft speed showed to have a strong impact on the predicted total noise, which matches the well-recognized sixth-power Mach number far-field sound intensity scaling law for airframe noise models, while the measurements indicated a less significant dependency. This is mainly due to installation effects and noise reduction measures that are not included in the models. Nevertheless, the variations in the spectra of the predicted and measured noise showed similar patterns.
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| 2. |
- Jardines, Aniel, et al.
(författare)
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Thunderstorm prediction during pre-tactical air-traffic-flow management using convolutional neural networks
- 2024
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Ingår i: Expert systems with applications. - : Elsevier BV. - 0957-4174 .- 1873-6793. ; 241, s. 122466-
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Tidskriftsartikel (refereegranskat)abstract
- Thunderstorms can be a large source of disruption for European air-traffic management causing a chaotic state of operation within the airspace system. In current practice, air-traffic managers are provided with imprecise forecasts which limit their ability to plan strategically. As a result, weather mitigation is performed using tactical measures with a time horizon of three hours. Increasing the lead time of thunderstorm predictions to the day before operations could help air-traffic managers plan around weather and improve the efficiency of air-traffic-management operations. Emerging techniques based on machine learning have provided promising results, partly attributed to reduced human bias and improved capacity in predicting thunderstorms purely from numerical weather prediction data. In this paper, we expand on our previous work on thunderstorm forecasting, by applying convolutional neural networks (CNNs) to exploit the spatial characteristics embedded in the weather data. The learning task of predicting convection is formulated as a binary-classification problem based on satellite data. The performance of multiple CNN-based architectures, including a fully-convolutional neural network (FCN), a CNN-based encoder–decoder, a U-Net, and a pyramid-scene parsing network (PSPNet) are compared against a multi-layer-perceptron (MLP) network. Our work indicates that CNN-based architectures improve the performance of point-prediction models, with a fully-convolutional neural-network architecture having the best performance. Results show that CNN-based architectures can be used to increase the prediction lead time of thunderstorms. Lastly, a case study illustrating the applications of convection-prediction models in an air-traffic-management setting is presented.
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| 3. |
- Maria Thoma, Evangelia, et al.
(författare)
-
Assessment of an Open-Source Aircraft Noise Prediction Model Using Approach Phase Measurements
- 2024
-
Ingår i: Journal of Aircraft. - : American Institute of Aeronautics and Astronautics (AIAA). - 0021-8669 .- 1533-3868. ; 61:3, s. 745-760
-
Tidskriftsartikel (refereegranskat)abstract
- An open-source simulation model for aircraft noise prediction is presented and validated using backpropagated noise measurements for a state-of-the-art engine and aircraft. The validation is focused on approach procedures and was performed using ground-based noise measurements that were taken at 17 recording stations for a total of 18 consecutive flights carried out during the morning of 8 April 2021. The flights were performed using two A321neo aircraft with LEAP-1A engines. It is demonstrated that the presented noise model provides a satisfactory estimation of the source noise for varying approach configurations and flight conditions. Configurations using a greater number of high-lift devices are particularly well predicted in the mid- and high-frequency regions, whereas the lower configuration settings show greater spectral deviations, which are partly attributed to measurement uncertainties caused by the increased aircraft–microphone distance. The model can predict the overall mean total sound intensity level within a 2 dB accuracy for all configurations, while the average predicted level at each microphone differs by less than 3 dB from the measurement average, for all cases except one. Variation in aircraft speed showed to have a strong impact on the predicted total noise, which matches the well-recognized sixth-power Mach number far-field sound intensity scaling law for airframe noise models, while the measurements indicated a less significant dependency. This is mainly due to installation effects and noise reduction measures that are not included in the models. Nevertheless, the variations in the spectra of the predicted and measured noise showed similar patterns.
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| 4. |
- Otero, Evelyn, 1983-
(författare)
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Acceleration of Compressible Flow Simulations with Edge Using Implicit Time Stepping
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Computational fluid dynamics (CFD) is a significant tool routinely used indesign and optimization in aerospace industry. Often cases with unsteadyflows must be computed, and the long compute times of standard methods hasmotivated the present work on new implicit methods to replace the standardexplicit schemes. The implementation and numerical experiments were donewith the Swedish national flow solver Edge, developed by FOI,universities, and collaboration partners.The work is concentrated on a Lower-Upper Symmetric Gauss-Seidel (LU-SGS)type of time stepping. For the very anisotropic grids needed forReynolds-Averaged Navier-Stokes (RANS) computations of turbulent boundary layers,LU-SGS is combined with a line-implicit technique. The inviscid flux Jacobians which contribute to the diagonalblocks of the system matrix are based on a flux splitting method with upwind type dissipation giving control over diagonal dominance and artificial dissipation.The method is controlled by several parameters, and comprehensivenumerical experiments were carried out to identify their influence andinteraction so that close to optimal values can be suggested. As an example,the optimal number of iterations carried out in a time-step increases with increased resolution of the computational grid.The numbering of the unknowns is important, and the numberings produced by mesh generators of Delaunay- and advancing front-type wereamong the best.The solver has been parallelized with the Message Passing Interface (MPI) for runs on multi-processor hardware,and its performance scales with the number of processors at least asefficiently as the explicit methods. The new method saves typicallybetween 50 and 80 percent of the runtime, depending on the case, andthe largest computations have reached 110M grid nodes. Theclassical multigrid acceleration for 3D RANS simulations was foundineffective in the cases tested in combination with the LU-SGS solverusing optimal parameters. Finally, preliminary time-accurate simulations for unsteady flows have shown promising results.
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| 5. |
- Otero, Evelyn, 1983-
(författare)
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Acceleration of Compressible Flow Simulations with Edge using Implicit Time Stepping
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Computational fluid dynamics (CFD) has become a significant tool routinely used in design and optimization in aerospace industry. Typical flows may be characterized by high-speed and compressible flow features and, in many cases, by massive flow separation and unsteadiness. Accurate and efficient numerical solution of time-dependent problems is hence required, and the efficiency of standard dual-time stepping methods used for unsteady flows in many CFD codes has been found inadequate for large-scale industrial problems. This has motivated the present work, in which major effort is made to replace the explicit relaxation methods with implicit time integration schemes. The CFD flow solver considered in this work is Edge, a node-based solver for unstructured grids based on a dual, edge-based formulation. Edge is the Swedish national CFD tool for computing compressible flow, used at the Swedish aircraft manufacturer SAAB, and developed at FOI, lately in collaboration with external national and international partners. The work is initially devoted to the implementation of an implicit Lower-Upper Symmetric Gauss-Seidel (LU-SGS) type of relaxation in Edge with the purpose to speed up the convergence to steady state. The convergence of LU-SGS has been firstly accelerated by basing the implicit operator on a flux splitting method of matrix dissipation type. An increase of the diagonal dominance of the system matrix was the principal motivation. Then the code has been optimized by means of performance tools Intel Vtune and CrayPAT, improving the run time. It was found that the ordering of the unknowns significantly influences the convergence. Thus, different ordering techniques have been investigated. Finding the optimal ordering method is a very hard problem and the results obtained are mostly illustrative. Finally, to improve convergence speed on the stretched computational grids used for boundary layers LU-SGS has been combined with the line-implicit method.
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| 6. |
- Otero, Evelyn, et al.
(författare)
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Acceleration on stretched meshes with line-implicit LU-SGS in parallel implementation
- 2015
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Ingår i: International journal of computational fluid dynamics (Print). - : Informa UK Limited. - 1061-8562 .- 1029-0257. ; 29:2, s. 133-149
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Tidskriftsartikel (refereegranskat)abstract
- The implicit lower-upper symmetric Gauss-Seidel (LU-SGS) solver is combined with the line-implicit technique to improve convergence on the very anisotropic grids necessary for resolving the boundary layers. The computational fluid dynamics code used is Edge, a Navier-Stokes flow solver for unstructured grids based on a dual grid and edge-based formulation. Multigrid acceleration is applied with the intention to accelerate the convergence to steady state. LU-SGS works in parallel and gives better linear scaling with respect to the number of processors, than the explicit scheme. The ordering techniques investigated have shown that node numbering does influence the convergence and that the orderings from Delaunay and advancing front generation were among the best tested. 2D Reynolds-averaged Navier-Stokes computations have clearly shown the strong efficiency of our novel approach line-implicit LU-SGS which is four times faster than implicit LU-SGS and line-implicit Runge-Kutta. Implicit LU-SGS for Euler and line-implicit LU-SGS for Reynolds-averaged Navier-Stokes are at least twice faster than explicit and line-implicit Runge-Kutta, respectively, for 2D and 3D cases. For 3D Reynolds-averaged Navier-Stokes, multigrid did not accelerate the convergence and therefore may not be needed.
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| 7. |
- Otero, Evelyn, et al.
(författare)
-
Convergence Acceleration of the CFD Code Edge by LU-SGS
- 2011
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Ingår i: 3rd CEAS European Air & Space Conference, Venice, 24-28 October 2011. - : CEAS/AIDAA. ; , s. 606-611
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Konferensbidrag (refereegranskat)abstract
- Edge is a flow solver for unstructured grids based on a dual grid and edge-based formulation. The standard dual-time stepping methods for compressible unsteady flows are inadequate for large-scale industrial problems. This has motivated the present work, in which an implicit Lower-Upper Symmetric Gauss-Seidel (LU-SGS) type of relaxation has been implemented in the code Edge with multigrid acceleration. Two different types of dissipation, a scalar and a matrix model, have been constructed which increase the diagonal dominance of the system matrix but not the numerical viscosity of the computed solution. A parametric study demonstrates convergence accelerations by a factor of three for inviscid transonic flows compared to explicit Runge-Kutta smoothing for multigrid acceleration.
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| 8. |
- Otero, Evelyn, 1983-, et al.
(författare)
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Flight Procedure Analysis for a Combined Environmental Impact Reduction : An Optimal Trade-Off Strategy
- 2022
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Ingår i: Aerospace. - : MDPI AG. - 2226-4310. ; 9:11, s. 683-683
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Tidskriftsartikel (refereegranskat)abstract
- Many attempts have been made to reduce aviation’s environmental impact, as aviation traffic has grown exponentially in recent decades. While some approaches focus on technology and fuel alternatives, others strive to develop improved operational measures within air traffic management as a short-term action to mitigate aviation-induced climate change, as well as air pollution. In this work, different flight procedures are analyzed in terms of emissions and noise impact to define optimal trade-offs. The investigation is based on flight data recorders, emissions, and noise prediction models. An aircraft trajectory simulation code with flight procedure optimization is also implemented to define an environmentally optimal trajectory. The results show that while noise and the emissions proportional to the burned fuel may be reduced for some trajectories, other non-CO2 emissions could drastically increase if too low idle-thrust levels are reached. Therefore, a minimum threshold for idle thrust is suggested as a key factor to define a truly optimal trajectory in terms of CO2 emissions, non-CO2 emissions, and noise.
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| 9. |
- Otero, Evelyn, et al.
(författare)
-
Implementation of Implicit LU-SGS method with Line-implicit scheme on Stretched Unstructured Grids
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A first implementation of line-implicit Lower-Upper Symmetric Gauss-Seidel (LU-SGS) in Edge has been considered in this paper for convergenceacceleration on stretched meshes. The motivation comes from the lack of efficiency of the implicit LU-SGS when running in RANS meshes. Edge is a flow solver for unstructured grids based on a dual grid and edge-based formulation. The line-implicit method has been implemented in the code Edge has an acceleration method when computing explicit schemes in stretched meshes. This methods works only in regions of stretched grid where the flow equations are integrated implicitly in time along the structured lines. The combination with an implicit LU-SGS should remove the restriction of the time step for explicit schemes and accelerate the convergence to steady state. The results have shown that for highly stretched meshes, line-implicit LU-SGS could perform much faster than LU-SGS.
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| 10. |
- Otero, Evelyn, et al.
(författare)
-
Parameter investigation for computing time reduction with Lower-Upper Symmetric Gauss-Seidel and line-implicit methods
- 2014
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Ingår i: AIAA AVIATION 2014 -7th AIAA Theoretical Fluid Mechanics Conference.
-
Konferensbidrag (refereegranskat)abstract
- An implicit Lower-Upper Symmetric Gauss-Seidel (LU-SGS) solver has been implemented as a multigrid (MG) smoother combined with a line-implicit method as an acceleration technique for Reynolds-Averaged Navier-Stokes (RANS) simulation on stretched meshes. The Computational Fluid Dynamics (CFD) code concerned is Edge, an edge- based finite volume Navier-Stokes flow solver for structured and unstructured grids. The paper focuses on the investigation of the parameters related to the novel line-implicit LU- SGS solver for convergence acceleration on 3D RANS meshes. The influence on the overall convergence of the Courant-Friedrichs-Lewy (CFL) number, the Left Hand Side (LHS) dissipation, and the convergence of iterative solution of the linear problem is presented and default values are defined for maximum convergence acceleration. These optimized set- tings are applied to 3D RANS computations for comparison with explicit and line-implicit Runge-Kutta (RK) smoothing. For most of the cases, a computing time acceleration of the order of 2 is found depending on the mesh type, namely the boundary layer and the magnitude of residual reduction.
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