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Browsing FE - DCA | Documentos por Auto-Depósito by Sustainable Development Goals (SDG) "13:Ação Climática"
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- Dual-Purpose Star Tracker and Space Debris Detector: Miniature Instrument for Small SatellitesPublication . Beltran Nadal Arribas; Maia, João G.; Castanheira, João Pedro Conceição ; Filho, Joel Alves Costa ; Melício, Rui; Gordo, Paulo Romeu Seabra; Onderwater, Hugo; Duarte, Rui; Silva, André Resende Rodrigues daThis paper presents the conception, design and real miniature instrument implementation of a dual-purpose sensor for small satellites that can act as a star tracker and space debris detector. In the previous research work, the authors conceived, designed and implemented a breadboard consisting of a computer laptop, a camera interface and camera controller, an image sensor, an optics system, a temperature sensor and a temperature controller. It showed that the instrument was feasible. In this paper, a new real star tracker miniature instrument is designed, physically realized and tested. The implementation follows a New Space approach; it is made with Commercial Off-the-Shelf (COTS) components with space heritage. The instrument’s development, implementation and testing are presented.
- How different are conventional and biofuel sprays applied to aviation? An infodynamic comparative analysisPublication . Ferrão, Inês Alexandra dos Santos ; Panão, Miguel Rosa Oliveira; Mendes, Miguel; Moita, Ana Sofia Oliveira Henriques; Silva, André Resende Rodrigues daThe transition from fossil to sustainable and alternative fuels is imperative to address environmental concerns and meet energy requirements. Thus, the implementation of alternative fuels requires a deeper investigation of spray behavior. This study explores conventional jet fuel (Jet A-1) and hydrotreated vegetable oil (HVO) in terms of breakup length and spray dynamics over a wide range of operating conditions. The normalized mean breakup length was measured, and an empirical correlation was developed based on the experimental data. Focusing on the droplet sizes in fuel sprays, which are critical for optimizing combustion, an informational perspective for comparative analysis was explored. The terms informature, infotropy, and infosensor were introduced to quantify and capture the non-deterministic nature of physical systems. The results revealed similar drop size distributions for HVO and Jet A-1, with the Gamma function effectively characterizing the distributions. Both fuels exhibit spray evolution toward higher complexity states, emphasizing the role of aerodynamic forces and minimum development distance in atomization. The new lexicon of infodynamics views sprays as networks of information flow, with infotropy indicating that both fuels produce sprays with similar degrees of transformation. HVO is endorsed as a viable alternative with broader implications for sustainable aviation solutions and understanding complex engineering processes.
- Mitigating Dynamic Stall with a Movable Leading-Edge: the NACA0012-IK30 WingPublication . Camacho, Emanuel António Rodrigues ; Silva, André Resende Rodrigues da ; Marques, Flávio D.One major problem that affects 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, used previously for thrust enhancement in flapping propulsion. An experimental rig is designed and built to study the advantages of a time-varying pitching leading edge on a plunging wing, more specifically its influence on the aerodynamic coefficients over time. Results indicate that when the wing is not experiencing significant stall, the movable leading edge does not hold considerable influence on drag or lift. However, it can reduce the pitching moment intensity by indirectly shifting the pressure center. Contrarily, when the wing is under proper dynamic stall, the movable leading edge truly improves the aerodynamic characteristics while operating at smaller effective angles of attack. 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.
- Predicting airfoil dynamic stall loads using neural networksPublication . Camacho, Emanuel António Rodrigues ; Silva, André Resende Rodrigues da ; Marques, Flávio D.Dynamic stall is an aerodynamic regime characterized by loss of airfoil lift, drag increment, and abrupt changes in the pitching moment. Such effects can couple with structural dynamics where perturbations can be easily amplified, making this a critical phenomenon that jeopardizes operational safety. Hence, there is always the need to constantly study the basics of dynamic stall and provide newer predictive models that can take advantage of the current interest peak in artificial intelligence. The present work builds upon that need, exploring the ability of a simple feed-forward network to predict the oscillation cycle of a pitching airfoil experiencing from light to deep stall of a NACA0012 airfoil close to a Reynolds number of approximately 1.1x10^6. The proposed neural network uses the angle of attack and its rate of change as inputs, then estimates the whole aerodynamic cycle at once, outputting an aggregated vector of drag, lift, and pitching moment coefficients. The training phase was conducted using a database containing several conditions obtained from experimental tests, with a strict convergence criterion of R^2=0.99 for both training and test datasets. Results show that the neural network, even in the least-performing conditions, can capture the aerodynamics and overall tendencies, even if some dynamics are underrepresented in the training dataset. The present work brings down the complexity of methodology while demonstrating that a simplistic architecture can still offer an accurate dynamic stall model.
- Splashing correlation for single droplets impacting liquid films under non-isothermal conditionsPublication . Rodrigues, Daniel de Almeida Vasconcelos ; Barata, Jorge Manuel Martins ; Silva, André Resende Rodrigues daThe droplet impact phenomenon onto liquid films is predominant in a variety of modern industrial applications, including internal combustion engines and cooling of electronic devices. These are characterised by heat and mass transfer processes, such as evaporation, condensation and boiling. However, studies regarding droplets and liquid films under non-isothermal conditions are scarce in the literature and do not explore temperature-dependent phenomena. Due to this, the main objective of this work is to evaluate the influence of temperature on the splashing occurrence of single droplets impinging onto liquid films under the presence of a heat flux. The crown evolution is evaluated qualitatively to provide insight regarding breakup mechanisms. Water, n-heptane and n-decane are the fluids considered for the current study, as these provide a wide range of thermophysical properties and saturation temperatures. The splashing dynamics are evaluated by varying the droplet impact velocity and dimensionless temperature of the liquid film. Qualitative results show that an increase in the liquid film temperature leads to the transition from spreading to splashing, which is less evident for fuels in comparison with water. For water and n-heptane, the formation of cusps on the crown rim is promoted, which is associated with ligament breakup. For n-decane, the crown rims are relatively homogeneous in terms of shape and size, whereas the atomisation process varies a function of the liquid film temperature. Visually, the secondary droplets exhibit a greater size in comparison with lower temperatures. Transitional regimes display some irregularities, such as splashing suppression/reduction, which require further attention. In terms of splashing correlation, the authors propose to develop a non-splash/splash boundary for both iso- and non-isothermal conditions. Results show that the splashing threshold is dependent on the thermophysical properties and the dimensionless temperature of the liquid film.
- Sustainable Aviation Fuels and their impact in commercial airport operationPublication . Magalhães, Leandro; Santos, Luis; Ferreira, Ana Filipa; Silva, André Resende Rodrigues daWith global air traffic projected to grow annually by approximately 3.8%, the aviation sector faces increasing pressure to implement effective strategies for mitigating its environmental impact, particularly with respect to greenhouse gas emissions. Sustainable Aviation Fuels represent a critical pathway for decarbonizing aviation by offering a lower-emission alternative to conventional jet fuels. This study evaluates the environmental impact of SAFs on specific operational phases of flight, with a focus on the landing and take-off cycle. A case study was conducted at Lisbon Airport using real aircraft movement data over a one-week period. Emissions were calculated by correlating aircraft engine types with data from the ICAO Engine Exhaust Emissions Databank. The analysis identifies the most emission-intensive flight phase, the most polluting fleet, and evaluates the potential GHG reductions achievable through the use of various SAF pathways. Additionally, operational alternatives for reducing emissions during the taxi phase, including APU management strategies, are examined. The results provide actionable insights into the role of SAFs in reducing airport-level emissions and support targeted interventions for more sustainable airport operations.
- Thrust force assessment of a MFC-actuated tail-like robotic fish using Unsteady Panel MethodPublication . Silva, Maíra Martins da ; Camacho, Emanuel António Rodrigues ; Silva, André Resende Rodrigues da ; Marques, Flávio D.Fish-like robots are used in various fields, such as environmental monitoring and underwater exploration. These devices are designed to emulate the motion of a real fish. They can have flexible bodies to mimic body/caudal-based locomotion patterns or fins to mimic median/paired fin-based locomotion patterns. Standard propulsion methods include oscillating fins, flapping tails, and body undulations. This work investigates a robotic fish with a flexible tail actuated by a Macro-Fiber Composite (MFC) pair in a bi-morph configuration. This device is designed to mimic body/caudal-based locomotion patterns; therefore, it should present propulsion capabilities due to its body undulations. These propulsion capabilities are assessed using the Unsteady Panel Method for different sinusoidal inputs. This method requires the device’s kinematics, which is derived using an analytical model based on the Euler–Bernoulli beam theory, considering the electro-mechanical coupling of the actuators. The mean thrust force derived using the Unsteady Panel Method is compared with the actual mean thrust acquired during an experimental campaign. The experimental and numerical results indicated that higher thrust forces can be achieved when the device is excited in its second resonance frequency. These results are in line with Lighthill’s findings.