414 research outputs found

    A reduced order modeling methodology for the parametric estimation and optimization of aviation noise

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    The successful mitigation of aviation noise is one of the key enablers of sustainable aviation growth. Technological improvements for noise reduction at the source have been countered by increasing number of operations at most airports. There are several consequences of aviation noise including direct health effects, effects on human and non-human environments, and economic costs. Several mitigation strategies exist including reduction of noise at source, land-use planning and management, noise abatement operational procedures, and operating restrictions. Most noise management programs at airports use a combination of such mitigation measures. To assess the efficacy of noise mitigation measures, a robust modeling and simulation capability is required. Due to the large number of factors which can influence aviation noise metrics, current state-of-the-art tools rely on physics-based and semi-empirical models. These models help in accurately predicting noise metrics in a wide range of scenarios; however, they are computationally expensive to evaluate. Therefore, current noise mitigation studies are limited to singular applications such as annual average day noise quantification. Many-query applications such as parametric trade-off analyses and optimization remain elusive with the current generation of tools and methods. There are several efforts documented in literature which attempt to speed up the process using surrogate models. Techniques include the use of pre-computed noise grids with calibration models for non-standard conditions. These techniques are typically predicated on simplifying assumptions which greatly limit the applicability of such models. Simplifying assumptions are needed to downsize the number influencing factors to be modeled and make the problem tractable. Existing efforts also suffer due to the inclusion of categorical variables for operational profiles which are not conducive to surrogate modeling. In this research, a methodology is developed to address the inherent complexities of the noise quantification process, and thus enable rapid noise modeling capabilities which can facilitate parametric trade-off analysis and optimization efforts. To achieve this objective, a research plan is developed and executed to address two major gaps in literature. First, a parametric representation of operational profiles is proposed to replace existing categorical descriptions. A technique is developed to allow real-world flight data to be efficiently mapped onto this parametric definition. A trajectory clustering method is used to group similar flights and representative flights are parametrized using an inverse-map of an aircraft performance model. Next, a field surrogate modeling method is developed based on Model Order Reduction techniques to reduce the high dimensionality of computed noise metric results. This greatly reduces the complexity of data to be modeled, and thus enables rapid noise quantification. With these two gaps addressed, the overall methodology is developed for rapid noise quantification and optimization. This methodology is demonstrated on a case study where a large number of real-world flight trajectories are efficiently modeled for their noise results. As each such flight trajectory has a unique representation, and typically lacks thrust information, such noise modeling is not computationally feasible with existing methods and tools. The developed parametric representations and field surrogate modeling capabilities enable such an application.Ph.D

    Rotor Fatigue Life Prediction and Design for Revolutionary Vertical Lift Concepts

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    Despite recent technological advancements, rotorcraft still lag behind their fixed-wing counterparts in the areas of flight safety and operating cost. Competition with fixed-wing aircraft is difficult for applications where vertical takeoff and landing (VTOL) capabilities are not required. Both must be addressed to ensure the continued competitiveness of vertical lift aircraft, especially in the context of new military and civilian rotorcraft programs such as Future Vertical Lift and urban air mobility, which will require orders-of-magnitude improvements in reliability, availability, maintainability, and cost (RAM-C) metrics. Lifecycle costs and accident rates are strongly driven by scheduled replacement or failure of flight-critical components. Rotor blades are life-limited to ensure that they are replaced before fatigue damage exceeds critical levels, but purchasing new blades is extremely costly. Despite aggressive component replacement times, fatigue failure of rotor blades continues to account for a significant proportion of inflight accidents. Fatigue damage in rotorcraft is unavoidable due to the physics of rotary-wing flight, but new engineering solutions to improve fatigue life in the rotor system could improve rotorcraft operating costs and flight safety simultaneously. Existing rotorcraft design methods treat fatigue life as a consequence, rather than a driver, of design. A literature review of rotorcraft design and fatigue design methods is conducted to identify the relevant strengths and weaknesses of traditional processes. In rotorcraft design, physics-based rotor design frameworks are focused primarily on fundamental performance analysis and do not consider secondary characteristics such as reliability or fatigue life. There is a missing link between comprehensive rotor design frameworks and conceptual design tools that prevents physics-based assessment of RAM-C metrics in the early design stages. Traditional fatigue design methods, such as the safe life methodology, which applies the Miner's rule fatigue life prediction model to rotorcraft components, are hindered by a lack of physics-based capabilities in the early design stages. An accurate fatigue life quantification may not be available until the design is frozen and prototypes are flying. These methods are strongly dependent on extrapolations built on historical fatigue data, and make use of deterministic safety factors based on organizational experience to ensure fatigue reliability, which can lead to over-engineering or unreliable predictions when applied to revolutionary vertical lift aircraft. A new preliminary fatigue design methodology is designed to address these concerns. This methodology is based on the traditional safe life methodology, but replaces several key elements with modern tools, techniques, and models. Three research questions are proposed to investigate, refine, and validate different elements of the methodology. The first research question addresses the need to derive physics-based fatigue load spectra more rapidly than modern comprehensive analysis tools allow. The second investigates the application of different probabilistic reliability solution methods to the fatigue life substantiation problem. The third question tests the ability of the preliminary fatigue design methodology to evaluate the relative impact of common preliminary fatigue design variables on the probability of fatigue failure of a conceptual helicopter's rotor blade. Hypotheses are formulated in response to each research question, and a series of experiments are designed to test those hypotheses. In the first experiment, a multi-disciplinary analysis (MDA) environment combining the rotorcraft performance code NDARC, the comprehensive code RCAS, and the beam analysis program VABS, is developed to provide accurate physics-based predictions of rotor blade stress in arbitrary flight conditions. A conceptual single main rotor transport helicopter based on the UH-60A Black Hawk is implemented within the MDA to serve as a test case. To account for the computational expense of the MDA, surrogate modeling techniques, such as response surface equations, artificial neural networks, and Gaussian process models are used to approximate the stress response across the flight envelope of the transport helicopter. The predictive power and learning rates of various surrogate modeling techniques are compared to determine which is the most suitable for predicting fatigue stress. Ultimately, shallow artificial neural networks are found the provide the best compromise between accuracy, training expense, and uncertainty quantification capabilities. Next, structural reliability solution methods are investigated as a means to produce high-reliability fatigue life estimates without requiring deterministic safety factors. The Miner's sum fatigue life prediction model is reformulated as a structural reliability problem. Analytical solutions (FORM and SORM), sampling solutions (Monte Carlo, quasi-Monte Carlo, Latin hypercube sampling, and directional simulation), and hybrid solutions importance sampling) are compared using a notional fatigue life problem. These results are validated using a realistic helicopter fatigue life problem \jnr{which incorporates the fatigue stress surrogate model and is based on a probabilistic definition of the mission spectrum to account for fleet-wide usage variations. Monte Carlo simulation is found to provide the best performance and accuracy when compared to the exact solution. Finally, the capabilities of the preliminary fatigue design methodology are demonstrated using a series of hypothetical fatigue design exercises. First, the methodology is used to predict the impact of rotor blade box spar web thickness on probability of fatigue failure. Modest increases in web thickness are found to reduce probability of failure, but larger increases cause structural instability of the rotor blade in certain flight regimes which increases the fatigue damage rate. Next, a similar study tests the impact of tail rotor cant angle. Positive tail rotor cant is found to improve fatigue life in cases where the center of gravity (CG) of the vehicle is strongly biased towards the tail, but is detrimental if the CG is closer to the main rotor hub station line. Last, the effect of design mission requirements like rate of climb and cruising airspeed is studied. The methodology is not sensitive enough to predict the subtle impact of changes to rate of climb, but does prove that a slower cruising airspeed will decrease probability of fatigue failure of the main rotor blade. The methodology is proven to be capable of quantifying the influence of \jnr{rotor blade design variables, vehicle layout and configuration, and certain design mission requirements}, paving the way for implementation in a rotorcraft design framework. This thesis ends with suggestions for future work to address the most significant limitations of this research, as well as descriptions of the tasks required to apply the methodology to conventional rotorcraft or conceptual revolutionary vertical lift aircraft.Ph.D

    Flow Dynamics and Aeroacoustics of Flow-induced Vibration of Bluff Bodies

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    Flow-induced vibration (FIV), a common phenomenon of fluid-structure interaction (FSI), is found everywhere and at all scales in the applications of marine, civil, aeronautical, and power engineering. The study of FIV phenomenology, ranging from fatigue and concomitant damage of structures to its exploitation for energy extraction, has been an active area of fundamental research. The research on the mechanism supporting the amplifying, stabilizing, and suppressing of FIV has practical implications for the structural design for optimal engineering fatigue control, energy utilization, etc. Moreover, the noise propagation generated from FIV is also accompanying environmental pollution that should not be ignored. However, past research on the FIV supported by nonlinear spring and the corresponding detailed FSI characteristics are limited. The present study will conduct a numerical FIV study of bluff bodies mounted by linear and nonlinear springs, and analyze the impact of stiffness nonlinearity on the FIV responses, including the amplitude variation, phase change, frequency variation, and wake pattern. The technical method used in this part is direct Computational Fluid Dynamics/Computational Structural Dynamics (CFD/CSD) simulation with the full-order model (FOM), via the coupled Navier-Stokes and body-structure equations. Additionally, the present study investigates the geometrical influences on FIV response and the mechanism underpinning the transfer from lock-in range to desynchronization or galloping range. Different body shapes, varied Reynolds numbers, and reduced velocity will involve many cases, as a result, expensive time will be consumed if the corresponding grids are generated and FOM calculations are carried out for each case. This part of the research will be mainly based on the data-driven stability analysis using the reduced-order model (ROM), and FOM based on CFD/CSD method will be used as supplementary for comparison. ROM could also provide the modal analysis and physical perspective that are not available for FOM. Combining ROM and FOM methods, this thesis explores the mode transformation and interaction in the lock-in behavior of laminar flow past a circular cylinder. For the galloping analysis, it is observed very small changes in the windward interior angle of an isosceles-trapezoidal body can provoke or suppress galloping---indeed, a small decrease or increase (low to 1°) of the windward interior angle from a right angle (90°) can result in a significant enhancement and complete suppression, respectively, of the galloping oscillations. This supports our hypothesis that the contraction and/or expansion of the cross-section in the streamline direction is significantly responsible for the galloping response. Furthermore, one novel methodology of data-driven stability analysis via the superposition of 2-D reduced-order modes (SROM) for the purpose of performing modal analysis and stability predictions of 3-D flow-induced vibration with spanwise shear inflow is presented. Lastly, noise propagation from energy harvesters based on the FIV mechanism also deserves attention. Owing that there is limited past research on noise propagation from oscillating cylinders, an investigation on aeroacoustics study of different oscillation patterns of single cylinder and tandem cylinders is carried out

    Prediction & Active Control of Multi-Rotor Noise

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    Significant developments have been made in designing and implementation of Advanced Air Mobility Vehicles (AAMV). However, wider applications in urban areas require addressing several challenges, such as safety and quietness. These vehicles differ from conventional helicopter in that they operate at a relatively lower Reynolds number. More chiefly, they operate with multiples of rotors, which may pose some issues aerodynamically, as well as acoustically. The aim of this research is to first investigate the various noise sources in multi-rotor systems. High-fidelity simulations of two in-line counter-rotating propellers in hover, and in forward flight conditions are performed. Near field flow and acoustic properties were resolved using Hybrid LES-Unsteady RANS approach. Far-field sound predictions were performed using Ffowcs-Williams-Hawkings formulation. The two-propeller results in hovering are compared with that of the single propeller. This enabled us to identify the aerodynamic changes resulting from the proximity of the two propellers to each other and to understand the mechanisms causing the changes in the radiated sound. It was discovered that there is a dip in the thrust due to the relative proximity of the rotors. Owing to this, there is also some acoustic banding above the rotors mainly because they operate at the same rotational rate. We then considered the forward flight case and compared it with the corresponding hovering case. This enabled us to identify the aerodynamic changes resulting from the incoming stream. By examining the near acoustic field, the far-field spectra, the Spectral Proper Orthogonal Decomposition, and by conducting periodic averaging, we were able to identify the sources of the changes to the observed tonal and broadband noise. The convection of the oncoming flow was seen to partially explain the observed enhancement in the tonal and BBN, compared to the hovering case. It is well known that High fidelity methods are critical in predicting the full spectrum of rotor acoustics. However, these methods can be prohibitively expensive. We present here an investigation of the feasibility of reduction methods such as Proper Orthogonal Decomposition as well as Dynamic Mode decomposition for reduction of data obtained via Hybrid Large-Eddy – Unsteady Reynolds Averaged Navier Stokes approach (HLES) to be used further to obtain additional parameters. Specifically, we investigate how accurate reduced models of the high-fidelity computations can be used to predict the far-field noise. It was found that POD was capable of reconstructing accurately the parameters of interest with 15-40% of the total mode energies, whereas the DMD could only reconstruct primitive parameters such as velocity and pressure loosely. A rank truncation convergence criterion \u3e 99.8% was needed for better performance of the DMD algorithm. In the far-field spectra, DMD could only predict the tonal contents in the lower- mid frequencies whiles the POD could reproduce all frequencies of interest. Lastly, we develop an active rotor noise control technology to reduce the in-plane thickness noise associated with multi-rotor Advanced Air Mobility Vehicles (AAMV). An actuation signal is determined via the Ffowcs-Williams-Hawking (FWH) formula. Two in-line rotors are considered and we showed that the FWH-determined actuation signal can produce perfect cancellation at a point target. However, the practical need is to achieve noise reduction over an azimuthal zone, not just a single point. To achieve this zonal noise reduction, an optimization technique is developed to determine the required actuation signal produced by the on-blade distribution of embedded actuators on the two rotors. For the specific geometry considered here, this produced about 9 dB reduction in the in-plane thickness noise during forward flight of the two rotors. We further developed a technology that replaces using a point actuator on each bladed by distributed micro actuators system to achieve the same noise reduction goal with significantly reduced loading amplitudes per actuator. Overall, this research deepens the knowledge base of multi-rotor interaction. We utilize several techniques for extracting various flow and acoustic features that help understand the dynamics of such systems. Additionally, we provide a more practical approach to active rotor noise control without a performance penalty to the rotor system

    80 Years of Aerospace Engineering Education in the Netherlands

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    This year, 2020, the Faculty of Aerospace Engineering at Delft University of Technology in the Netherlands celebrates its 80th birthday. This paper describes the history of the department since its founding in early 1940, just before the start of World War II in the Netherlands, until present day. The paper will highlight how its research and education developed within the socio-economic context of the Netherlands and the developments in aerospace over the past 80 years

    7° Jornadas ITEE 2023

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    En esta publicación se reúnen los trabajos y resúmenes extendidos presentados en las VII Jornadas de Investigación, Transferencia, Extensión y Enseñanza (ITEE), de la Facultad de Ingeniería de la Universidad Nacional de La Plata, organizadas por la Secretaría de Investigación y Transferencia de dicha facultad, que tuvieron lugar entre el 25 y el 27 de abril de 2023.Facultad de Ingenierí

    Engineering 3D architected metamaterials for enhanced mechanical properties and functionalities.

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    Compared with conventional materials, architected metamaterials have shown unprecedented mechanical properties and functionalities applications. Featured with controlled introduction of porosity and different composition, architected metamaterials have demonstrated unprecedent properties not found in natural materials. Such design strategies enable researchers to tailor materials and structures with multifunctionalies and satisfy conflicting design requirements, such as high stiffness and toughness; high strength with vibration mitigation properties, etc. Furthermore, with the booming advancement of 3D printing technologies, architected materials with precisely defined complex topologies can be fabricated effortlessly, which in turn promotes the research significantly. The research objectives of this dissertation are to achieve the enhanced mechanical properties and multifunctionalities of architected metamaterials by integrative design, computational modeling, 3D printing, and mechanical testing. Phononic crystal materials are capable of prohibiting the propagation of mechanical waves in certain frequency ranges. This certain frequency ranges are represented by phononic band gaps. Formally, band gaps are formed through two main mechanisms, Bragg scattering and local resonance. Band gaps induced by Bragg scattering are dependent on periodicity and the symmetry of the lattice. However, phononic crystals with Bragg-type band gaps are limited in their application because they do not attenuate vibration at lower frequencies without requiring large geometries. It is not practical to build huge models to achieve low frequency vibration mitigation. Alternatively, band gaps formed by local resonance are due to the excitation of resonant frequencies, and these band gaps are independent of periodicity. Therefore, lower frequency band gaps have been explored mostly through the production of phononic metamaterials that exploit locally resonant masses to absorb vibrational energy. However, despite research advances, the application of phononic metamaterials is sill largely hindered by their limited operation frequency ranges. Designing lightweight phononic metamaterials with low-frequency vibration mitigation capability is still a challenging topic. On the other hand, conventional phononic crystals usually exhibit very poor mechanical properties, such as low stiffness, strength, and energy absorption. This could largely limit their practical applications. Ideally, multifunctional materials and structures with both vibration mitigation property and high mechanical performance are demanded. In this work, we propose architected polymer foam material to overcome the challenges. Beside altering the topological architecture of metamaterials, tailoring the composition of materials is another approach to enhance the mechanical properties and realize multifunctionalities. Natural materials have adopted this strategy for long period of time. Biological structural materials such as nacre, glass sea sponges feature unusual mechanical properties due to the synergistic interplay between hard and soft material phases. These exceptional mechanical performance are highly demanded in engineering applications. As such, intensive efforts have been devoted to developing lightweight structural composites to meet the requirements. Despite the significant advances in research, the design and fabrication of low-cost structural materials with lightweight and superior mechanical performance still represent a challenge. Taking inspiration from cork material, we propose a new type of multilayered cellular composite (MCC) structure composed of hard brittle and soft flexible phases to tackle this challenge. On the other hand, piezoelectric materials with high sensitivity but low energy absorption have largely limited their applications, especially during harsh environment where external load could significantly damage the materials. Enlightened by the multiphase composite concept, we apply this design motif to develop a new interpenetrating-phased piezoelectric materials by combining PZT material as skeleton and PDMS material as matrix. By using a facial camphene-templated freeze-casting method, the co-continuous composites are fabricated with good quality. Through experiment and simulation studies, the proposed composite demonstrates multifunction with exceptional energy absorption and high sensitivity. Based on the above experimental studies, we further propose to use topology optimization framework to obtain the composites with the best performance of multifunctionalities. Specifically, we will use the solid isotropic material with penalization (SIMP) approach to optimize the piezoelectric materials with multi-objectives of 1) energy absorption and 2) electric-mechanical conversion property. The materials for the optimization design will be elastic PZT as skeleton and elatic material PDMS as matrix. To enable the gradient search of objective function efficiently, we will use adjoint method to derive the shape sensitivity analysis

    CHALLENGES AND ISSUES OF MODERN SCIENCE

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    The “Challenges and Issues of Modern Science” collection comprises scientific research on relevant topics related to the latest advancements in various fields of science. Emphasis is placed on developing aerospace technology, thermodynamics and energy, mechanical engineering, materials science and technologies, automation, electronics and telecommunications, information technology, project management, ecology, and industrial and environmental safety. It can be helpful for professionals in the respective fields, scientists, educators, and students. The presented material will help readers expand their knowledge of diverse approaches to solving current scientific and practical issues. The papers are published in the author's edition. До збірника «Виклики та проблеми сучасної науки» увійшли наукові праці з актуальних тем, що пов’язані з найновішими досягненнями в різних галузях науки. Акцентується увага на розвитку аерокосмічної техніки, термодинаміки та енергетики, машинобудування, матеріалознавства та технологій, автоматизації, електроніки та телекомунікацій, інформаційних технологій, управління проектами, екології, промислової та екологічної безпеки. Може бути корисним для фахівців у відповідних галузях, науковців, викладачів та студентів. Поданий матеріал допоможе читачам розширити знання про різноманітні підходи до розв’язання актуальних науково-практичних задач. Матеріали публікуються в авторській редакції

    STAB-Jahresbericht 2023 - Proceedings of the 21st STAB-Workshop 2023 in Göttingen

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    Die STAB-Jahresberichte werden als Sammlung der Kurzfassungen der Vorträge an die Teilnehmer der abwechselnd stattfindenden Symposien und Workshops verteilt. So erscheint der vorliegende STAB-Jahresbericht 2023 anlässlich des 21. STAB-Workshops, der am 7. und 8. November 2023 in Göttingen stattfinden wird. Der Bericht enthält 77 Mitteilungen über Arbeiten aus den Fachgruppen, die auf dem Workshop vorgestellt werden. Den Mitteilungen ist ein Inhaltsverzeichnis (Seite 14 bis Seite 19) vorangestellt, das nach Fachgruppen gegliedert ist. Innerhalb der Fachgruppen sind die Beiträge alphabetisch nach Autoren geordnet. Die Beiträge verteilen sich (bezogen auf die Erstautoren) zu 4 % auf die Industrie, zu 39 % auf Hochschulen und zu 57 % auf Forschungseinrichtungen (DLR, DNW, ISL). Die Autoren und Koautoren dieses Berichts sind auf den Seiten 174 und 175 aufgeführt
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