Doctorat en Ciència i Tecnologia Aeroespacials
http://hdl.handle.net/2117/184556
2021-07-26T21:11:42ZOptimization of the progress variable definition using a genetic algorithm for the combustion of complex fuels
http://hdl.handle.net/2117/350010
Optimization of the progress variable definition using a genetic algorithm for the combustion of complex fuels
Both, Ambrus; Mira Martínez, Daniel; Lehmkuhl Barba, Oriol
In this work counterflow diffusion flamelets of n-heptane and air are used at stable and unsteady extinguishing conditions for building a thermo-chemical database for Computational Fluid Dynamics (CFD) calculations. The injectivity of the progress variable definition is achieved through an optimization process using a genetic algorithm in combination with an adequate objective function.
2021-07-23T10:24:25ZBoth, AmbrusMira Martínez, DanielLehmkuhl Barba, OriolIn this work counterflow diffusion flamelets of n-heptane and air are used at stable and unsteady extinguishing conditions for building a thermo-chemical database for Computational Fluid Dynamics (CFD) calculations. The injectivity of the progress variable definition is achieved through an optimization process using a genetic algorithm in combination with an adequate objective function.High-fidelity simulations of the mixing and combustion of a technically premixed hydrogen flame
http://hdl.handle.net/2117/350008
High-fidelity simulations of the mixing and combustion of a technically premixed hydrogen flame
Mira Martínez, Daniel; Both, Ambrus; Lehmkuhl Barba, Oriol; Gomez Gonzalez, Samuel; Forck, Jonathan; Tanneberger, Tom; Stathopoulos, Panagiotis; Paschereit, Christian Oliver
Numerical simulations are used here to obtain further understanding on the flashback mechanism of a technically premixed hydrogen flame operated in lean conditions. Recent work from the authors (Mira et al., 2020) showed that the hydrogen momentum strongly influences the flame dynamics and plays a fundamental role on the stability limits of the combustor. The axial injection influences the vortex breakdown position and therefore, the propensity of the burner to produce flashback. This work is an extension of our previous work where we include a detailed description of the mixing process and the influence of equivalence ratio fluctuations and heat loss on the flame dynamics.
2021-07-23T10:16:58ZMira Martínez, DanielBoth, AmbrusLehmkuhl Barba, OriolGomez Gonzalez, SamuelForck, JonathanTanneberger, TomStathopoulos, PanagiotisPaschereit, Christian OliverNumerical simulations are used here to obtain further understanding on the flashback mechanism of a technically premixed hydrogen flame operated in lean conditions. Recent work from the authors (Mira et al., 2020) showed that the hydrogen momentum strongly influences the flame dynamics and plays a fundamental role on the stability limits of the combustor. The axial injection influences the vortex breakdown position and therefore, the propensity of the burner to produce flashback. This work is an extension of our previous work where we include a detailed description of the mixing process and the influence of equivalence ratio fluctuations and heat loss on the flame dynamics.Semi implicit solver for high fidelity LES/DNS solutions of reacting flows
http://hdl.handle.net/2117/350007
Semi implicit solver for high fidelity LES/DNS solutions of reacting flows
Surapaneni, Anurag; Mira Martínez, Daniel
A semi-implicit/point-implicit stiff solver (ODEPIM) for integrating chemistry in context of high fidelity LES/DNS simulations is presented. A detailed overview of the algorithm and its numerical formulation is discussed. The solver is then compared against a state-of-the-art multi-order implicit solver CVODE in terms of accuracy and costs. It was found that for typical LES/DNS timestep sizes ODEPIM was about one order faster than CVODE, which would make it a compelling alternative to pure implicit methods. ODEPIM, as mentioned in the literature depends on a fixed sub-timestep size to do the integration steps, this limits the speedup that can be achieved by the solver. A modification to the ODEPIM algorithm to determine the sub-timestep size dynamically is proposed enabling greater speedup. Solutions of a triple flame problem obtained using static and dynamic ODEPIM solvers are compared against the reference solutions obtained with CVODE. The dynamic ODEPIM solver was found to use the maximum permissible sub-timestep size, which on average was 8 to 4 times higher that the fixed sub-timestep size of the static ODEPIM solver. The size of the sub-timestep size directly correlates to the cpu cost, hence the dynamic ODEPIM solver is significantly faster than the static solver, this improvement however, comes at negligible loss in accuracy.
2021-07-23T10:08:52ZSurapaneni, AnuragMira Martínez, DanielA semi-implicit/point-implicit stiff solver (ODEPIM) for integrating chemistry in context of high fidelity LES/DNS simulations is presented. A detailed overview of the algorithm and its numerical formulation is discussed. The solver is then compared against a state-of-the-art multi-order implicit solver CVODE in terms of accuracy and costs. It was found that for typical LES/DNS timestep sizes ODEPIM was about one order faster than CVODE, which would make it a compelling alternative to pure implicit methods. ODEPIM, as mentioned in the literature depends on a fixed sub-timestep size to do the integration steps, this limits the speedup that can be achieved by the solver. A modification to the ODEPIM algorithm to determine the sub-timestep size dynamically is proposed enabling greater speedup. Solutions of a triple flame problem obtained using static and dynamic ODEPIM solvers are compared against the reference solutions obtained with CVODE. The dynamic ODEPIM solver was found to use the maximum permissible sub-timestep size, which on average was 8 to 4 times higher that the fixed sub-timestep size of the static ODEPIM solver. The size of the sub-timestep size directly correlates to the cpu cost, hence the dynamic ODEPIM solver is significantly faster than the static solver, this improvement however, comes at negligible loss in accuracy.An OpenFOAM set-up for simulating thermal winds in mountain/valley configurations
http://hdl.handle.net/2117/349249
An OpenFOAM set-up for simulating thermal winds in mountain/valley configurations
Athota, Rathan Babu; Rojas Gregorio, José Ignacio; Arias Calderón, Santiago; Villardi de Montlaur, Adeline de
2021-07-14T09:43:20ZAthota, Rathan BabuRojas Gregorio, José IgnacioArias Calderón, SantiagoVillardi de Montlaur, Adeline deActive flow control optimisation on SD7003 airfoil at pre and post-stall angles of attack using synthetic jets
http://hdl.handle.net/2117/348596
Active flow control optimisation on SD7003 airfoil at pre and post-stall angles of attack using synthetic jets
Monshi Tousi, Navid; Coma Company, Martí; Bergadà Granyó, Josep Maria; Pons Prats, Jordi; Mellibovsky Elstein, Fernando; Bugeda Castelltort, Gabriel
The use of Active Flow Control (AFC) technologies to modify the forces acting on streamlined bodies is one of the most active research fields in aerodynamics. For each particular application, finding the optimum set of AFC parameters which maximises lift, minimises drag or maximises lift-to-drag ratio (aerodynamic efficiency), has become a necessary design requirement. In the present paper, the AFC technology was applied to the Selig-Donovan 7003 (SD7003) airfoil at Reynolds number 6 × 104. Synthetic jets were employed to modify the lift and drag forces acting on the airfoil. Four angles of attack (AoA) of 4¿, 6¿, 8¿ and 14¿ were considered, alongside five AFC parameters: jet position, jet width, momentum coefficient, forcing frequency and jet inclination angle. A multi objective optimisation based on genetic algorithms (GA) was performed for each angle of attack to find the optimum combination of AFC parameters. Each GA generation was simulated using Computational Fluid Dynamics (CFD). A home-made GA package was linked with a mesh generator and the CFD solver, and the results were automatically fed back to the GA code. Over 2200 CFD simulations were performed in two dimensions, using the SpalartAllmaras turbulent model. The motivation behind the current study is to understand the dependence of the optimum set of AFC parameters on the AoA. Results show that, as AoA is increased, the potential benefits of AFC become more pronounced, which allows for considerable improvement in aerodynamic efficiency. The physics involved in the interaction between the main flow and synthetic jet are clearly presented and clarifies that the physical phenomenon to obtain maximum efficiency is completely different at pre-stall and post-stall AoA. In particular, the aerodynamic efficiency was increased by 251% from baseline (no actuation) by using a moderate/finite momentum coefficient at AoA=14¿, while a mere 39% increase was obtained at AoA=8¿. In addition, the interaction between the incoming flow and the synthetic jet pulsating flow at different injection angles has been thoroughly investigated
2021-07-06T11:20:33ZMonshi Tousi, NavidComa Company, MartíBergadà Granyó, Josep MariaPons Prats, JordiMellibovsky Elstein, FernandoBugeda Castelltort, GabrielThe use of Active Flow Control (AFC) technologies to modify the forces acting on streamlined bodies is one of the most active research fields in aerodynamics. For each particular application, finding the optimum set of AFC parameters which maximises lift, minimises drag or maximises lift-to-drag ratio (aerodynamic efficiency), has become a necessary design requirement. In the present paper, the AFC technology was applied to the Selig-Donovan 7003 (SD7003) airfoil at Reynolds number 6 × 104. Synthetic jets were employed to modify the lift and drag forces acting on the airfoil. Four angles of attack (AoA) of 4¿, 6¿, 8¿ and 14¿ were considered, alongside five AFC parameters: jet position, jet width, momentum coefficient, forcing frequency and jet inclination angle. A multi objective optimisation based on genetic algorithms (GA) was performed for each angle of attack to find the optimum combination of AFC parameters. Each GA generation was simulated using Computational Fluid Dynamics (CFD). A home-made GA package was linked with a mesh generator and the CFD solver, and the results were automatically fed back to the GA code. Over 2200 CFD simulations were performed in two dimensions, using the SpalartAllmaras turbulent model. The motivation behind the current study is to understand the dependence of the optimum set of AFC parameters on the AoA. Results show that, as AoA is increased, the potential benefits of AFC become more pronounced, which allows for considerable improvement in aerodynamic efficiency. The physics involved in the interaction between the main flow and synthetic jet are clearly presented and clarifies that the physical phenomenon to obtain maximum efficiency is completely different at pre-stall and post-stall AoA. In particular, the aerodynamic efficiency was increased by 251% from baseline (no actuation) by using a moderate/finite momentum coefficient at AoA=14¿, while a mere 39% increase was obtained at AoA=8¿. In addition, the interaction between the incoming flow and the synthetic jet pulsating flow at different injection angles has been thoroughly investigatedNetwork-based ionospheric gradient monitoring to support GBAS
http://hdl.handle.net/2117/346619
Network-based ionospheric gradient monitoring to support GBAS
Caamaño Albuerne, María; Felux, Michael; Gerbeth, Daniel; Juan Zornoza, José Miguel; González Casado, Guillermo; Sanz Subirana, Jaume
Ionospheric anomalies, like large ionospheric gradients, might produce a difference between the ionospheric error experienced bythe Ground Based Augmentation System (GBAS) reference station and the aircraft on approach. This ionospheric delay differencecould lead to hazardous position errors if undetected.For that reason, the GBAS Approach Service Types (GAST) C and D provide solutions against this threat, but the methodsemployed still face challenges by limiting the availability in certain cases, especially in regions with severe ionospheric conditions.This issue is caused by the use of very conservative ionospheric threat models derived based on the worst-ever-experiencedionospheric gradients in the relevant region. However, these worst-case gradients occur very rarely.Therefore, this paper proposes a methodology capable of detecting ionospheric gradients in real-time and estimating theirparameters in near real-time by using a wide area network of dual-frequency and multi-constellation GNSS monitoring stations.Hence, the GBAS stations could use this information to update the threat model currently applied in their algorithms, which wouldresult in an improvement of the GBAS availability in regions where it is degraded.The detection and estimation algorithm is initially theoretically explained. Then, the performance of this algorithm is evaluatedwith simulated gradients and with a real gradient, utilizing for both the real measurements recorded by a reference networkin Alaska. The synthetic gradients are simulated over the nominal real measurements from this network and all the gradientparameters are modified within their ranges in the already existing threat models. In this way, we assess the performance of ouralgorithm by comparing the differences between the known simulated gradient parameters and the parameters estimated by ouralgorithm. Additionally, we also evaluate our algorithm with one real ionospheric gradient measured by the same network inAlaska to study the differences between using simulated gradients and real gradients.
2021-06-04T07:11:14ZCaamaño Albuerne, MaríaFelux, MichaelGerbeth, DanielJuan Zornoza, José MiguelGonzález Casado, GuillermoSanz Subirana, JaumeIonospheric anomalies, like large ionospheric gradients, might produce a difference between the ionospheric error experienced bythe Ground Based Augmentation System (GBAS) reference station and the aircraft on approach. This ionospheric delay differencecould lead to hazardous position errors if undetected.For that reason, the GBAS Approach Service Types (GAST) C and D provide solutions against this threat, but the methodsemployed still face challenges by limiting the availability in certain cases, especially in regions with severe ionospheric conditions.This issue is caused by the use of very conservative ionospheric threat models derived based on the worst-ever-experiencedionospheric gradients in the relevant region. However, these worst-case gradients occur very rarely.Therefore, this paper proposes a methodology capable of detecting ionospheric gradients in real-time and estimating theirparameters in near real-time by using a wide area network of dual-frequency and multi-constellation GNSS monitoring stations.Hence, the GBAS stations could use this information to update the threat model currently applied in their algorithms, which wouldresult in an improvement of the GBAS availability in regions where it is degraded.The detection and estimation algorithm is initially theoretically explained. Then, the performance of this algorithm is evaluatedwith simulated gradients and with a real gradient, utilizing for both the real measurements recorded by a reference networkin Alaska. The synthetic gradients are simulated over the nominal real measurements from this network and all the gradientparameters are modified within their ranges in the already existing threat models. In this way, we assess the performance of ouralgorithm by comparing the differences between the known simulated gradient parameters and the parameters estimated by ouralgorithm. Additionally, we also evaluate our algorithm with one real ionospheric gradient measured by the same network inAlaska to study the differences between using simulated gradients and real gradients.Flight planning in multi-unmanned aerial vehicle systems: Nonconvex polygon area decomposition and trajectory assignment
http://hdl.handle.net/2117/346597
Flight planning in multi-unmanned aerial vehicle systems: Nonconvex polygon area decomposition and trajectory assignment
Skorobogatov, Georgy; Barrado Muxí, Cristina; Salamí San Juan, Esther; Pastor Llorens, Enric
Nowadays, it is quite common to have one unmanned aerial vehicle (UAV) working on a task but having a team of UAVs is still rare. One of the problems that prevent us from using teams of UAVs more frequently is flight planning. In this work, we present the first open-source solution ( https://pypi.org/project/pode/ ) for splitting any complex area into multiple parts. The area of interest can be convex or nonconvex and can include any number of no-flight zones. Four solutions, based on the algorithm of Hert and Lumelsky, are tested with the aim of improving the compactness of the partitions. We also show how the shape of the partitions influences flight performance in a real case scenario.
2021-06-03T13:02:55ZSkorobogatov, GeorgyBarrado Muxí, CristinaSalamí San Juan, EstherPastor Llorens, EnricNowadays, it is quite common to have one unmanned aerial vehicle (UAV) working on a task but having a team of UAVs is still rare. One of the problems that prevent us from using teams of UAVs more frequently is flight planning. In this work, we present the first open-source solution ( https://pypi.org/project/pode/ ) for splitting any complex area into multiple parts. The area of interest can be convex or nonconvex and can include any number of no-flight zones. Four solutions, based on the algorithm of Hert and Lumelsky, are tested with the aim of improving the compactness of the partitions. We also show how the shape of the partitions influences flight performance in a real case scenario.A methodology for semi-automatic documentation of archaeological elements using RPAS imagery
http://hdl.handle.net/2117/345652
A methodology for semi-automatic documentation of archaeological elements using RPAS imagery
Angelats Company, Eduard; Parés Calaf, Maria Eulàlia; Mas-Florit, Catalina; Cau-Ontiveros, Miguel Àngel
One of the main tasks of archaeologists is to document (map) their sites at a level where stones may be clearly distinguished and to provide centimetre-level reliable measurements of man-built structures.One of the goals of the project ARCHREMOTELANDS is to develop a methodology to generate those maps semi-automatically combiningRPAS imagery, photogrammetry and machine learning technique
2021-05-17T06:49:43ZAngelats Company, EduardParés Calaf, Maria EulàliaMas-Florit, CatalinaCau-Ontiveros, Miguel ÀngelOne of the main tasks of archaeologists is to document (map) their sites at a level where stones may be clearly distinguished and to provide centimetre-level reliable measurements of man-built structures.One of the goals of the project ARCHREMOTELANDS is to develop a methodology to generate those maps semi-automatically combiningRPAS imagery, photogrammetry and machine learning techniqueA persistent scatterer interferometry procedure to monitor urban subsidence
http://hdl.handle.net/2117/345486
A persistent scatterer interferometry procedure to monitor urban subsidence
Crosetto, Michele; Monserrat, Oriol; Barra, Anna; Cuevas-González, Maria; Krishnakumar, Vrinda; Mróz, Marek; Crippa, Bruno
This paper describes a Persistent Scatterer Interferometry procedure for deformation monitoring. Its more original part concerns an
approach to estimate the atmospheric phase component. The procedure can be used to monitor deformation areas that are relatively
small and are surrounded by stable areas. The proposed procedure is described step by step. The procedure can be applied using SAR
data coming from different sensors. However, in this work we discuss results obtained using Sentinel-1 data. A case study is described,
where the deformation is caused by water pumping associated with construction works. In this case study, a stack of 78 Sentinel-1
images were analysed. The main part of the paper concerns the analysis of the atmospheric component. A comprehensive
characterization of this component is first described, considering the original non-filtered phases. This is followed by the
characterization of the residual filtered phases. This analysis highlights the goodness of the proposed procedure. This is further
confirmed by the analysis of two deformation time series. The procedure can work with any type of deformation phenomena, provided
that its spatial extension is sufficiently small.
2021-05-12T09:42:44ZCrosetto, MicheleMonserrat, OriolBarra, AnnaCuevas-González, MariaKrishnakumar, VrindaMróz, MarekCrippa, BrunoThis paper describes a Persistent Scatterer Interferometry procedure for deformation monitoring. Its more original part concerns an
approach to estimate the atmospheric phase component. The procedure can be used to monitor deformation areas that are relatively
small and are surrounded by stable areas. The proposed procedure is described step by step. The procedure can be applied using SAR
data coming from different sensors. However, in this work we discuss results obtained using Sentinel-1 data. A case study is described,
where the deformation is caused by water pumping associated with construction works. In this case study, a stack of 78 Sentinel-1
images were analysed. The main part of the paper concerns the analysis of the atmospheric component. A comprehensive
characterization of this component is first described, considering the original non-filtered phases. This is followed by the
characterization of the residual filtered phases. This analysis highlights the goodness of the proposed procedure. This is further
confirmed by the analysis of two deformation time series. The procedure can work with any type of deformation phenomena, provided
that its spatial extension is sufficiently small.Air traffic management and systems IV: selected papers of the 6th ENRI International Workshop on ATM/CNS (EIWAC2019) - Analysis of weather impact on flight efficiency for Stockholm Arlanda airport arrivals
http://hdl.handle.net/2117/345478
Air traffic management and systems IV: selected papers of the 6th ENRI International Workshop on ATM/CNS (EIWAC2019) - Analysis of weather impact on flight efficiency for Stockholm Arlanda airport arrivals
Lemetti, Anastasia; Polishchuk, Tatiana; Sáez García, Raúl; Prats Menéndez, Xavier
Analysis of punctuality of airport arrivals, as well as identification of causes of the delays within transition airspace, is an important step in evaluating performance of the Terminal Maneuvering Area (TMA) Air Navigation Services. In this work we analyse how different weather events influence arrival punctuality and vertical flight efficiency on example of Stockholm Arlanda airport. We quantify the impact of the deviations from the flight plans influenced by different weather events, by demonstrating that they result in significant arrival delays, vertical inefficiencies and calculating how much extra fuel is wasted due to vertical flight inefficiency within Stockholm TMA.
2021-05-12T08:06:13ZLemetti, AnastasiaPolishchuk, TatianaSáez García, RaúlPrats Menéndez, XavierAnalysis of punctuality of airport arrivals, as well as identification of causes of the delays within transition airspace, is an important step in evaluating performance of the Terminal Maneuvering Area (TMA) Air Navigation Services. In this work we analyse how different weather events influence arrival punctuality and vertical flight efficiency on example of Stockholm Arlanda airport. We quantify the impact of the deviations from the flight plans influenced by different weather events, by demonstrating that they result in significant arrival delays, vertical inefficiencies and calculating how much extra fuel is wasted due to vertical flight inefficiency within Stockholm TMA.