APRÈN. Portal de la producció docent del professorat de la UPC

Active Flow Control (AFC) techniques are currently being in the spotlight of researchers because of its capabilities to improve significantly the aerodynamic performance of airfoils. This bachelor thesis focuses on the use of Synthetic Jet Actuators (SJA) to improve the performance of the NACA 0012 profile at post-stall angles of attack and high Reynolds numbers. This purpose was carried on by performing Computational Fluid Dynamics (CFD) simulations using pisoFoam, a transient Reynolds-Averaged Navier-Stokes (RANS) solver, and using the Spalart-Allmaras (S-A) turbulence model. The mesh consisted in a hybrid (containing unstructured and structured grids) C-type mesh, widely used for airfoil simulations. The studied airfoil was the NACA 0012 profile in the post-stall angle of attack alpha=19º at a Reynolds number Re=2e6. After performing a mesh dependence study, comparing the results with experimental wind tunnel literature, the SJA actuated simulations were performed. The results concluded that the use of SJA could significantly improve the aerodynamics of the non-actuated case, finding that the non-dimensional frequency F+ and the momentum coefficient C_mu of the jet had a major impact on the behavior of the airflow, specially influenced by the latter.

This thesis addresses the study of advanced avionics systems for an electric Vertical Take-Off and Landing (ONA Jet) aircraft. It focuses on developing communication and navigation systems. These vehicles are designed to operate in urban environments, where precise and safe control are essential. The main objective of the thesis is to adapt and improve the existing avionics system, enhancing its autonomous capabilities and improving flight efficiency and safety. To achieve this, cutting-edge technologies in communication, navigation, and automation are integrated. This not only reduces the pilot's workload but also improves operational safety and efficiency. A detailed analysis of flight management and navigation systems is conducted. Route planning and precise GPS navigation systems are critical for handling the complex take-off and landing operations. Additionally, surveillance and monitoring systems provide real-time data on engine status and battery levels, which is crucial for operating in urban environments with many obstacles. The thesis also addresses the importance of Human-Machine Interfaces (HMI), which allow pilots to interact intuitively and efficiently with the aircraft through touchscreen displays and other advanced interfaces. The use of the Garmin G3000 integrated flight system is highlighted, recognized for its advanced technology and ease of use. Another key aspect is the study for the development of an Autonomous Take-Off and Landing (ATOL) systems. Various sensor-based technologies, such as vision, LiDAR, and radar, are evaluated to ensure safe and reliable autonomous operations. Additionally, an intelligent voice assistant is proposed to reduce the pilot's workload and facilitate single-pilot operations, aiming towards fully autonomous flights in the future. Finally, the thesis explores future technologies such as advanced phased array antennas, software-defined radios (SDR), and 5G connectivity, which have the potential to significantly improve the precision of communication and the operational efficiency of avionics systems. A detailed and advanced plan for the implementation of avionics systems in the ONA Jet is presented, with a strong focus on integrating cutting-edge technologies to enhance safety, efficiency, and sustainability in urban aviation.

En el context actual, la sostenibilitat energètica i la reducció de l'impacte ambiental dels edificis són reptes fonamentals en la lluita contra el canvi climàtic. Els edificis consumeixen una part significativa de l'energia global i contribueixen de manera notable a les emissions de gasos amb efecte d'hivernacle. Per aquest motiu, la recerca de solucions innovadores per a la seva eficiència energètica és crucial. Entre les diferents estratègies possibles, la integració de fonts d'energia renovable en l'entorn construït ha guanyat rellevància, i l'energia eòlica es presenta com una opció amb un gran potencial. Aquest treball sorgeix de la voluntat d'explorar la viabilitat d'implementar sistemes de generació eòlica a l'edifici de l'EETAC, amb l'objectiu de convertir-lo en un espai més autosuficient i sostenible. Aprofitant les característiques del vent a la zona, es planteja un estudi aerodinàmic basat en simulacions de dinàmica de fluids computacional (CFD). S'ha desenvolupat un model computacional utilitzant el programa OpenFOAM, aplicant el mètode LES per analitzar els patrons de flux i identificar les zones amb major potencial eòlic. Els resultats mostren que les vores d'atac de l'edifici, especialment a 2-3 metres sobre el terrat, presenten velocitats del vent que poden duplicar la velocitat del flux lliure, indicant un bon potencial per a la generació d'energia. Tot i així, es destaquen limitacions en el modelatge i la qualitat de la malla, que han afectat la precisió dels resultats. Per aquest motiu, es recomana aprofundir en futurs estudis amb models alternatius (com RANS) i considerant factors addicionals com la presència d'edificis propers i variacions en les condicions del vent. Aquest estudi proporciona una base preliminar per a la implementació de tecnologies d'energia renovable en entorns urbans i contribueix als objectius de sostenibilitat de la UPC.

The evolution of aerodynamics since the last century has led to its implementation in many sectors. One such sector is the automotive industry, where car manufacturers have been competing for years to reduce aerodynamic drag in order to sell more fuel-efficient cars. This industry need has carried over to high level racing, where teams in different championships around the world have long since had to focus all their efforts on achieving better aerodynamic performance than the rest in order to achieve victories. This has also been reflected at an educational level, where competitions such as Formula Student have carved out a niche for developing future engineers in the skills required for the industry. This project focuses on optimizing the aerodynamic performance of the front wing of an electric Formula Student car through design, simulation, and analysis. Using only computer simulations, the project uses 3D modelling and computational fluid dynamics (CFD) in order to examine various designs and find the best solution. The primary objective of the project is to study the aerodynamic performance of the front wing at various angles of attack. By focusing on reducing drag and maximizing downforce, the project aims to find an ideal balance that improves the car's stability and speed. Each design iteration is evaluated to assess its effectiveness. This evaluation is essential for the Formula Student team's competitive plan, as aerodynamic efficiency is key to reducing lap times and improving performance on the track. The study of this aerodynamic performance has shown purely satisfactory values, yet it has also revealed several critical areas for design refinement. Addressing these potential improvements will require further in-depth analysis and optimization efforts in future studies.

In recent years, eVTOLs have emerged as a promising technological innovation in the field of urban air mobility, driven by the need for more sustainable, efficient, and versatile transportation solutions in densely populated areas. These aircraft offer a potential alternative to traditional ground transport, addressing urban congestion, reducing emissions, and providing faster, more flexible means of mobility. Their design, however, introduces new challenges. This project is centered on the design of a wing-tail configuration for an eVTOL aircraft, giving special attention to the interaction between both components, which plays a critical role in determining overall flight performance. The primary objective of the study is to determine the sizing, shaping, and positioning of the wing and the tail, assessing how the forces and moments generated by these components interact and affect the aircraft's behavior, while complying with the requirements given by ONAerospace. To achieve this, a preliminary design of both components has been carried out under free-stream conditions, focusing on their individual aerodynamic performance. Subsequently, an iterative process has been employed to analyze the combined lift and moment contributions, with special attention given to their impact on the aircraft's stability and ability to maintain a constant altitude. Computational tools such as SolidWorks have been used for geometric 3D modeling, while MATLAB has been employed to compute, refine, and plot the aerodynamic parameters. The results indicate that the wing design, based on empirical data, meets the expected lift production requirements across the specified flight conditions without needing design changes. The NACA 6412 airfoil utilized in the wing configuration contributes to stable lift production, eliminating the need for hyper-lift devices. The tail design, selected using volume coefficients, effectively balances the aircraft's moments. The achieved stability margin of 45.51% ensures that the aircraft remains stable and responsive, despite its prioritization of stability for medical applications. The aerodynamic efficiency, reflected by a lift-to-drag ratio between 10 and 13, is an acceptable value given the operational constraints. These results confirm that the final wing-tail design successfully meets the project's stability and performance criteria. However, future studies could further optimize efficiency by exploring alternative materials and conducting structural analyses.

The cavity flow problem is of high interest for two main reasons: it is a benchmark in computational fluid mechanics for validating different numerical solvers of the Navier-Stokes equation, and it acts as a test benchmark for studying a variety of fluid flow phenomena. In this study, we will focus on the square cavity four-lid-driven by the tangential motion of its four sides at the same speed, with opposite walls moving in opposite directions. The fluid motion is determined by solving the Navier-Stokes equation. This study focuses on the periodic solutions that arise for this configuration. The problem is regularized by setting the wall speed to follow a double-exponential distribution to avoid corner singularities caused by the discontinuities of the velocity at the boundary. This allows for exponential convergence in spectral discretization schemes. The time integration of the discretized Navier-Stokes equation is carried out by the Implicit Euler Method. Limit cycles are found by the Newton-Krylov numerical solver, in which the method intends to search for the roots of the equation that compares a given initial state of the flow with a state after time integration has been applied. In particular, we study the upper and lower limits of the Long Periodic Orbit (LPO), mentioned in some recent studies, as well as, the behavior past these critical values. The lower bound the orbit disappears in a Heteroclinic bifurcation caused by the collision with an unstable steady state. On the other hand, at the upper bound the flow becomes chaotic. Finally, a Hopf bifurcation has been identified recently but no periodic orbit arising from it has been reported. This Hopf bifurcation is found to be subcritical.

The aerospace industry has been in operation for more than 100 years, since the beginning of the 20th century, this sector has always been at the forefront of technology and therefore constantly changing. Today, thanks to it, we have managed to reach limits that were unimaginable in those years. Surpassing the speed of sound, reaching higher in the sky than ever before, even reaching into space. For this purpose of speed and range, companies such as Reaction Engines Ltd were born, developing an engine capable of reaching Mach 5, using innovative cooling systems for its turbojet engine such as the precooler system. But what if we could further improve this turbojet engine by adding, in addition to the precooler, a cooling system mostly used in commercial turbofan engines, such as the intercooler system? With the idea of improving the actual technology of turbojet engines, this project performs an analysis, at supersonic and hypersonic flight conditions, studying the effects and results of implementing both cooling systems simultaneously to the same thermodynamic cycle. To achieve this goal, the experimental engine cycle is simulated using a MATLAB application, which reproduces the processes happening inside this turbojet and shows result in a graphic and numerical way in order to be compared it with simulations done before with only one of the cooling systems mentioned above. Concluding with a study of the feasibility of the engine's manufacture taking into account current materials and technology and discussing the economic and industrial implications of the development of the mentioned engine.

This project aims to re-design and analyze the aerodynamics of a Low-Boom Supersonic Business Jet (SSBJ) to minimize sonic boom impact while maintaining efficient supersonic travel capabilities. The primary objective is to improve the lift-to-drag ratio of the aircraft, thus enhancing its aerodynamic efficiency and ensuring its feasibility for overland flight. The methodology includes the use of Computer-Aided Design (CAD) and Computational Fluid Dynamics (CFD). The CAD design is performed using SolidWorks, which enables precise modeling and iterative modifications of the jet's components. This process involves the integration of various design elements to optimize the overall aerodynamic profile. The CFD analysis is conducted using Ansys Fluent 2022R2, where simulations are based on the Euler equations to capture the high-speed compressible flow characteristics of the aircraft. These simulations help in evaluating the aerodynamic performance under different flight conditions, focusing on minimizing the sonic boom while achieving efficient aerodynamic performance. The redesign is anticipated to offer a 15% efficiency improvement and a higher value of the lift-to-drag ratio compared to the original configuration, aligning with the project's objectives. For future work, it is essential to complete the test matrix and conduct a mission simulation of the aircraft to verify that it is a better configuration. The findings are validated through a series of simulations that demonstrate improved performance metrics across various flight scenarios, confirming the success of the design modifications. This project is organized into five chapters: Introduction, Low-Boom Supersonic Business Jet Design, Methodology, Results, and Conclusions. Each chapter provides a logical progression from the historical context and design requirements to the detailed analysis and final conclusions.

This work focuses on a parametric study of the implementation of Active Flow Control (AFC) on the Selig-Donovan 7003 (SD7003) airfoil at $Re=60,000$ and $\alpha=13^{\circ}$, employing the Reynolds-Averaged Navier-Stokes (RANS) resolution method through the open-source computational fluid dynamics (CFD) software OpenFOAM. The Spalart-Allmaras model has been applied for turbulence modeling. Active Flow Control involves the implementation of a synthetic jet aiming to increase the kinetic energy of the boundary layer, preventing or delaying its separation, and thereby improving the aerodynamic performance of the airfoil. In the initial phase of the investigation, an analysis was conducted to verify the effects of implementing an inactive synthetic jet on aerodynamic performance. It has been confirmed that the presence of the jet slot on the airfoil does not entail serious losses in aerodynamic efficiency during flight phases for which it remains off, such as cruise. Specifically, the maximum loss resulted in a $\Delta \eta = -1.65$ at $\alpha=8^{\circ}$. The two geometric parameters were determined based on conclusions drawn from previous studies. Regarding the angle $\theta_j$, its selection was based on the better aerodynamic efficiency observed with tangential angles rather than normal to the wall. As for the location of the jet, $x_j = 0.0082C$ was chosen, with $C$ being the airfoil chord. The most relevant dynamic parameter of the study, subjected to a parametric study, is the dimensionless frequency $F^+$, which was varied within the interval $F^+ = [1.0, 4.0]$ with increments of $\Delta F^+ = 0.2$. Among all simulated configurations, particularly promising results were obtained for $F^+ = 3.0$, with aerodynamic efficiency improving by $233.67\%$ compared to the base case, with an increase in lift coefficient of $\Delta C_l = 60.3\%$ and a reduction in drag coefficient of $\Delta C_d = -51.9\%$. In the baseline case with the inactive jet, the formation of a recirculation bubble near the leading edge was observed. In contrast, in the actuated case with the optimal configuration, a significant reduction in the recirculation bubble on the upper surface of the airfoil was evident, reducing the associated drag and delaying flow detachment, thereby expanding the area of the airfoil that generated lift.

The economic and industrial development since the establishment of small satellites has been spectacular. Today, they offer a wide variety of services such as Earth Observation, Communications and IoT, Geolocation and space exploration. Due to this great growth, there are more and more small satellites in orbit. As a result, if their trajectories are not modified once their useful life is over, the probability of collision between them is increasing. For this reason they need a propulsion system to be able to maneuver. This has implied the need for the search of very efficient propellant systems with the smallest possible size, to implement them in small satellites. In addition, being such a competitive sector, apart from the optimization of space, it is also sought to reduce weight and consumption in order to bring the best technology at the lowest possible cost. Xiroi's Plugim Electrospray Thruster offers low power consumption, high performance and high thrust density, offering very high efficiency compared to other options on the market. It also uses a more economical propellant compared to the gases used, for example in Hall Effect Thruster (HET). In order to optimize the consumption, weight and volume of the thruster, this project aims to search and develop a simple and functional pressurization system. The most important requirements to be fulfilled by the company are: - The system must be composed of two tanks and must fit in 0.5U. - There must fit 550g of propellant in the system. - The pressure inside the tank should be around - 50 ¿¿¿¿ (± 5 ¿¿¿¿). - There should be a way to control the flow of the propellant. - Theoretical mass flow rate of 4. 4597 × 10¿5 ¿/¿. Through a preliminary design phase, a total of 5 prototypes have been porposed in order to think out of the box and find innovative alternatives in the sector. The most developed designs are prototypes 1, 3 and 5, which are based on a spring mechanism, a constant force mechanism and a toothed mechanism system, respectively. For each prototype configuration an experiment has been carried out without exerting pressure, with the aim of obtaining the mass flow due to the force of gravity and subsequently being able to compare it with the results by applying the corresponding system. Prototypes 3 and 5 are the most optimistic to reach a final version. On the one hand, the constant force mechanism has achieved a mass flow of 1 g/s higher than that obtained by gravity. On the other hand, although we have not been able to test the toothed mechanism due to printing problems, we have investigated and studied the operation and location of the gears for correct operation. Finally, simple and innovative prototypes have been achieved, thus fulfilling part of the objectives. On the other hand, experimentally it has been difficult to reach the pressure and mass flow requirements due to highly precise values and the limited resolution of the 3D prints. Nevertheless, the results have helped to make great advances in Xiroi's thruster that allow further development of the pressurization system, establishing a base on which to work and iterate.

Since the aerospace world began to rise, it has been under constant development, reaching milestones that nobody believed as possible in the beginnings. During all this time, new ideas appeared as a solution to the new challenges that came abroad with the evolution of the sector as it showed itself as one of the sectors with more potential. Sometimes, these new ideas rendered obsolete those of the moment or left their applications limited to very particular ones. A pretty good example is the reality of the turbojet engines nowadays. Since the turbofan engines appeared, the aforementioned use began to decrease, but they never became obsolete. At the moment turbojet engines are still used for certain applications, specially in military ones. But, what would happen if these engines could be updated and upgraded with the new technologies? Would they be used for more applications? The answer is affirmative, as it can be seen in cases as the one associated to Reaction Engines Ltd. This British company is in charge of developing the adaptable turbojet to rocket engine that will drive the Skylon space-plane from the ESA (European Space Agency). This aircraft has the objective to achieve the first space flight with a horizontal take-off. With the idea of improving the actual turbojet engines, this project intends to perform an analysis on the effects and results of implementing heat exchangers in different points of the motor. Concretely, it analyzes the effect of applying inter-cooling or pre-cooling. The turbojet engine flying conditions are in the hypersonic regime to follow the same conditions as in the SABRE-ESA project. The conditions selected are in order to analyze the effects of the aforementioned heat exchangers in such extreme situations. To perform this study, a simulator which intends to reproduce with high fidelity the processes happening inside the turbojet has been developed. This simulator shows result either in a graphic or numerical way and enables to modify the cycle with pre-cooling or inter-cooling. The analysis for which the simulator has been developed, is based on the ideal and the real cycle of both configurations in order to made a comparison between them and obtain conclusions. Finally, it also shows the losses effects due to the real heat exchanger selected. It has to be noted that the study is performed on each modification separately.

Airbus currently offers a wide range of cabin configurations, fuel tanks and cargo compartments for each of its aircraft models. All these configuration differences must be subjected to an amount of studies to ensure the operability and safety of the aircraft. One of the most critical and rigorous studies that each aircraft must overcome is the level of fuselage shear. The study consists of ensuring that the amount of shear suffered by the fuselage is lower than or equal to the safety values stipulated by Airbus. This verification process takes a long time and by that increases the computational and monetary costs for the company. This thesis deals with the development, implementation and verification of a new tool in order to offer solutions when the shear of an aircraft exceeds the reference and safety values. The aim is to reduce the amount of time and expenses for the certification of the aircrafts. First of all, the software that Airbus currently uses to calculate all the shear levels of the fuselage has been analyzed in detail. In a second step all requirements for the new tool development are discussed and reviewed with the Airbus stakeholders. After that the requested software is generated including the corresponding User Interface. Then the new tool has to be checked by a series of tests and certifications in order to ensure its operability in the industrial context by helping in the certification process of an aircraft.

In the automotive world, one of the key concepts at the time of the study is the aerodynamics of the vehicle. Within this sector, Formula 1 racing cars in particular, are the most demanding when it comes to complying with good aerodynamics to achieve the highest possible efficiency and thus achieve high speeds with good grip to the ground. The objective of the TFG is based on the aerodynamic study of the NACA0012 profile as a simplified model of a wing of a formula 1 car, which is subject to geometric variations in the suction surface of the profile. Specifically, two types of modifications will be applied: one will be based on the use of humps, while the other will be based on the use of dimples. Both types will deal with different aspects of the design to be studied, as well as the position and depth, as well as the angle of attack of the wing. Once the designs with the desired changes in the surface of the extraction are obtained, they will be analyzed by 3D simulations with the software OpenFOAM to study its aerodynamics through the results and determine whether the modifications applied in the profile help to improve its efficiency. After analyzing the values obtained in the simulations, it is concluded that none of the new modifications help to improve the aerodynamic profile. The added protuberances are extended along the spanwise direction, that is, they are not 3D protuberances, with the use of 3D protuberances, the three-dimensional effects they would cause could be very different from those obtained.

Today, the evolution of aviation is accelerating and getting faster. We are in a stage of innovation and creativity that leads us to new goals and challenges in all areas of the aerospace sector. In this project, in collaboration with ONAerospace, an eVTOL has been designed as an air ambulance and personal vehicle. It all started with a kind of Fiat-500 airplane, it was going to be practical and efficient. It was originally supposed to be a 4-passenger model, but eventually evolved to 6. In emergency situations, every second counts and we cannot let ourselves be affected by the aerodynamic drag. For this reason, the fuselage needed a change, the purpose of this work has been to reduce the Drag as much as possible and see how the design behaves at low speeds and high angles of attack. To achieve this, the fuselage has been parameterized and modifications have been made to see the effects in terms of aerodynamic resistance. On the other hand, combinations of these modifications have also been made to find the optimal fuselage. To be able to see these effects, first the set-up has been prepared for Ansys Fluent and two independence studies have been made to find the most accurate results as possible: Fluid domain independence study and mesh independence study. After that, the parameters have been changed and combined. The results obtained were as expected since the effects of all combined cases of the parameters modifications have been summed up and the optimal fuselage has been found. After that, the study of its behavior at high angles of attack and at low speed has shown that it can generate a little bit of lift, but the drag increases significantly. Further research should be done on the new structure and on drag reduction improvement with active control or new designs that make the shape more symmetrical and, thus, the body is streamlined and smoother.

EVTOLs (Electric Vertical Takeoff and Landing) are electric vehicles that, as their name suggests, can land and take off vertically, without the need for a runway like a conventional aircraft would. This innovative concept allows us to envision a different world from what we have today, especially with an initiative called Urban Air Mobility (UAM). Urban Air Mobility is a potential new form of aviation that aims to implement EVTOL technology within cities. The goal is to reduce the widespread use of combustion vehicles that currently exist, in order to mitigate the CO2 emissions that contribute to pollution. In recent years, many companies have emerged seeking to capitalize on this opportunity, and among them is the startup ONAerospace. The project involves developing an EVTOL capable of performing operations within the city and also executing rescue and/or medical assistance missions, which is another significant functionality of these vehicles due to their ability to land in confined spaces. This thesis involves designing a tail for ONAerospace's EVTOL, specifically a V-tail. This type of tail is quite common on EVTOLs due to its lightweight nature and structural benefits compared to a conventional tail. To design the tail, the following steps. First, parameters for a conventional T-tail were calculated, and then the conversion to a V-tail was performed, which provides the same aerodynamic performance as the previously designed conventional tail. Additionally, an aerodynamic study was conducted using Computational Fluid Dynamics (CFD) with the Ansys Fluent program to find the optimal wing profile for the aircraft tail. All the work has been done in coordination with the other authors involved in the design of the various parts of the aircraft.