FE - DCA | Documentos por Auto-Depósito
Permanent URI for this collection
Browse
Recent Submissions
- Flapping Airfoil Aerodynamics using Recurrent Neural NetworkPublication . Pereira, João A.; Camacho, Emanuel A. R.; Marques, Flávio D.; Silva, AndréThe recent increase in interest in artificial intelligence and neural networks has stirred up various industries. Inevitably, its application will trickle down to the most fundamental studies, for instance, unsteady aerodynamics. The present paper serves the purpose of exploring the ability of a recurrent neural network to predict flapping airfoil aerodynamics, in particular the lift coefficient of a plunging NACA0012 airfoil. Thus, a neural network is designed and trained using motion parameters, such as motion frequency and effective angle of attack, to output the instantaneous lift coefficient over a plunging period. Training data is generated using a panel code (HSPM) for fast generation and early testing. Results show that the neural network can adequately predict the lift coefficient for various conditions, including plunging kinematics that are far from the training domain. Future work will build on this framework and extend it to other aerodynamic coefficients using CFD results and experiments, which should enhance the value of the estimates.
- Dynamic Stall Mitigation Using a Deflectable Leading Edge: The IK30 MechanismPublication . Camacho, Emanuel A. R.; Silva, A. R. R.; Marques, Flávio D.One major problem affecting rotor blade aerodynamics is dynamic stall, characterized by a series of events where transient vortex shedding negatively affects drag and lift, leading to abrupt changes in the wing’s pitching moment. The present work focuses on the mitigation of such effects by using a modified NACA0012 airfoil—the NACA0012-IK30 airfoil—previously used for thrust enhancement in flapping propulsion. An experimental rig is designed to study the advantages of a deflectable leading edge on a plunging and pitching wing, more specifically its influence on the aerodynamic coefficients over time. In the first stage, results indicate that the proposed IK30 mechanism does mitigate the stall effects under static conditions, with stall visualization data corroborating it. Regarding time-varying conditions, the data presents the adequacy of the proposed geometry under different plunging and pitching conditions, which, when correctly used, can mitigate or even eradicate the adverse effects of dynamic stall experienced, leading to significant drag reductions and modest lift enhancements. In the absence of a dynamic stall, the movable leading edge can also provide operational advantages, where it does not negatively affect drag or lift but can reduce the pitching moment intensity by indirectly shifting the pressure center. This study contributes to the long-standing discussion on how to mitigate the adverse effects of dynamic stall by providing an innovative yet simple solution.
- Influence of aluminum nanoparticles in alternative fuel: Single droplet combustion experiments and modelingPublication . Ferrão, Inês; Mendes, Tomás; Mendes, Miguel; Moita, A. S.; Silva, A. R. R.In this work, the effect of adding aluminum nanoparticles on hydrotreated vegetable oil was investigated experimentally and numerically in terms of nanofuel stability and single droplet combustion. The purpose is to understand the phenomena related to isolated droplet combustion when metallic particles are added to a liquid biofuel. Falling droplet combustion experiments were conducted in a drop tube furnace at two different furnace temperatures (800 C and 1000 C) using a high-speed camera coupled with a high magnification lens to investigate the droplet size evolution as disruptive burning phenomena. In numerical terms, a simplified macroscopic model was developed to predict the burning behavior of isolated nanofuel droplets, considering hexadecane as a surrogate fuel for the biofuel. The results reveal that adding nanoparticles resulted in a departure from the -law. Moreover, an increase in the overall droplet burning rate was observed, and according to the numerical results, nanoparticle radiation absorption is the responsible mechanism. Micro-explosions occurred for all nanofuels, and this disruptive burning behavior substantially influenced the droplet lifetime.
- Housekeeping System for Suborbital Vehicles: VIRIATO Mock-Up Vehicle Integration and TestingPublication . Rodrigues, Geraldo; Arribas, Beltran; Melício, Rui; Gordo, Paulo; Valério, Duarte; Casaleiro, J.; Silva, AndréThe work presented in this paper regards the improvement of a housekeeping system for data acquisition of a suborbital vehicle (VIRIATO rocket or launcher). The specifications regarding the vehicle are presented and hardware is chosen accordingly, considering commercial off-the-shelf components. Mechanical and thermal simulations are performed regarding the designed system and a physical prototype is manufactured, assembled and programmed. Functional and field test results resorting to unmanned aerial vehicles, as well as the system’s integration within VIRIATO project’s mock-up vehicle, are presented. These tests demonstrate the viability of this system as an independent data acquisition system, and simulation results show that commercial off-the-shelf components have the capability of surviving expected launch environments.
- List of Departures from LIS Airport from March 7, 2023 until March 13, 2023Publication . Fernandes, Ricardo; Magalhães, Leandro; Ferreira, Ana FilipaThis document contains statistical data from one week, including the real number of departures for each type of aircraft (engine) at Lisbon airport (LIS). The analysis was conducted from March 7, 2023 until March 13, 2023. The chosen period was based on the application of the randomness criterion and availability to obtain this information. The traffic sample for the referred period is obtained from an online database (Flight Radar 2024) which keeps data relatively to all the arrivals and departure from LIS airport. The data acquired by the database is from different sources, the main one being Automatic Dependent Surveillance-Broadcast (ADS-B). According to the analyzed data available at ANAC, the period under analysis, regarding the monthly traffic variation at the airport, represents approximately an average month (only around 4.6% below the average monthly movements for the year 2023), which seems appropriate for this analysis given that the aim is to achieve an annual average of movements and emissions. This fact has been observed for the current year, a fact that is in line with previous years. It was also observed that February corresponds to the month with the lowest air traffic, and the month of August represents the peak of operations at the airport under analysis.
- List of Arrivals from LIS Airport from March 7, 2023 until March 13, 2023Publication . Fernandes, Ricardo; Magalhães, Leandro; Ferreira, Ana FilipaThis document contains statistical data from one week, including the real number of arrivals for each type of aircraft (engine) at Lisbon airport (LIS). The analysis was conducted from March 7, 2023 until March 13, 2023. The chosen period was based on the application of the randomness criterion and availability to obtain this information. The traffic sample for the referred period is obtained from an online database (Flight Radar 2024) which keeps data relatively to all the arrivals and departure from LIS airport. The data acquired by the database is from different sources, the main one being Automatic Dependent Surveillance-Broadcast (ADS-B). According to the analyzed data available at ANAC, the period under analysis, regarding the monthly traffic variation at the airport, represents approximately an average month (only around 4.6% below the average monthly movements for the year 2023), which seems appropriate for this analysis given that the aim is to achieve an annual average of movements and emissions. This fact has been observed for the current year, fact that is in line with previous years. It was also observed that February corresponds to the month with the lowest air traffic, and the month of August represents the peak of operations at the airport under analysis.
- Red blood cell membrane-camouflaged gold-core silica shell nanorods for cancer drug delivery and photothermal therapyPublication . Rodrigues, Ana Carolina F.; Correia, I.J.; Moreira, André F.Gold core mesoporous silica shell (AuMSS) nanorods are multifunctional nanomedicines that can act simultaneously as photothermal, drug delivery, and bioimaging agents. Nevertheless, it is reported that once administrated, nanoparticles can be coated with blood proteins, forming a protein corona, that directly impacts on nanomedicines’ circulation time, biodistribution, and therapeutic performance. Therefore, it become crucial to develop novel alternatives to improve nanoparticles’ half-life in the bloodstream. In this work, Polyethylenimine (PEI) and Red blood cells (RBC)-derived membranes were combined for the first time to functionalize AuMSS nanorods and simultaneously load acridine orange (AO). The obtained results revealed that the RBC 41 derived membranes promoted the neutralization of the AuMSS’ surface charge and consequently improved the colloidal stability and biocompatibility of the nanocarriers. Indeed, the in vitro data revealed that PEI/RBC-derived membranes’ functionalization also improved the nanoparticles’ cellular internalization and was capable of mitigating the hemolytic effects of AuMSS and AuMSS/PEI nanorods. In turn, the combinatorial chemo-photothermal therapy mediated by AuMSS/PEI/RBC_AO nanorods was able to completely eliminate HeLa cells, contrasting with the less efficient standalone therapies. Such data reinforce the potential of AuMSS nanomaterials to act simultaneously as photothermal and chemotherapeutic agents.
- Heat transfer effect on the modeling of jets under supercritical and transcritical conditionsPublication . Magalhães, Leandro; Silva, A. R. R.; Barata, Jorge M MThe injection of nitrogen under supercritical and transcritical conditions, where the injection temperature is below nitrogen’s critical point, but the pressure is above it, is considered in this paper. While the scientific community recognizes that the sharp gradients of the different thermophysical parameters make it inappropriate to employ a two-phase flow modeling at conditions above the critical point, the issue is not restrained to the mere representation of turbulence for a mono-phase flow. Instead, a quantitative similarity with gas-jet-like behavior led to proposing an incompressible but variable density hypothesis suitable for describing supercritical and sub/near-critical conditions. Presently, such an approach is extended and assessed for a configuration including injector heat transfer. As such, axial density and temperature decay rates and jet spreading rates of density and temperature are evaluated, indicating a higher mixing efficiency in the supercritical regime and an overall dominance of heat propagation over momentum transport, with a greater preponderance in the supercritical regime.
- Influence of bubble growth and liquid film instabilities on droplet impact phenomena under saturated boiling regimesPublication . Vasconcelos, Daniel; Silva, A. R. R.; Barata, Jorge M MEvaporation and boiling are processes that occur in many industrial applications involving multiphase flows. For liquid films, however, studies are scarce regarding heat and mass transfer mechanisms and require further research. The main objective of this work is to evaluate bubble formation and detachment, followed by the impact phenomena. Therefore, an experimental setup was built and adapted for this purpose. A borosilicate glass impact surface is placed over a heat source, which consists of an aluminum block with four embedded cartridge heaters that heat the liquid film by conduction. Water and n-heptane are the fluids adopted for the experimental study, as the differences in thermophysical properties allow for a wider range of experiments. Study cases include dimensionless temperatures of θ > 0.6 for similar impact conditions. In terms of bubble formation, n-heptane displays smaller bubble diameters and higher release rates, whereas water exhibits larger bubbles and lower rates. Qualitatively, liquid film temperatures close to the saturation temperature do not reveal a direct influence on the crown development and posterior secondary atomization. For later stages of the impact, the central jet height and breakup are influenced by the film temperature, which is associated with the variation of thermophysical properties.
- The impact of revolutionary aircraft designs on global aviation emissionsPublication . Abrantes, Ivo; Ferreira, Ana F.; Magalhães, Leandro; Costa, Mário; Silva, AndréThe discussion about the environmental impact caused by aviation has gained greater prominence due to the increased demand for this sector and, consequently, the increase in the number of flights. Environmental concerns have stimulated the development of novel approaches to reduce pollutants and CO2 emissions. This study aims to assess the impact of disruptive concepts on commercial aircraft by reducing CO2 emissions by 50% by 2050. In this regard the fleet system dynamics model is used to assess the effects of technological progress on future air transport systems. It accounts for the manufacturer’s production capabilities and current projections and forecasts on the needs and evolution of global air transport, as well as their expected entry into service. The main factors reported were production capacity, year of entry of the technology/concept, and the transport capacity and range of aircraft. The sensitivity study on the production capacity of new aircraft/concepts showed that with a 15% increase, emissions can be reduced between 1 and 2.6%, depending on the case and scenario. On the other hand, increasing the aircraft production capacity could lead to a problem of overcapacity.