ORCID Profile
0000-0002-6058-9094
Current Organisations
RMIT University
,
Clarkson University
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Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 11-2013
DOI: 10.2514/1.C032145
Publisher: Informa UK Limited
Date: 13-04-2011
Publisher: Elsevier BV
Date: 12-2020
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 2010
DOI: 10.2514/1.40463
Publisher: Wiley
Date: 18-03-2011
DOI: 10.1002/WE.462
Publisher: Informa UK Limited
Date: 02-01-2019
Publisher: ASMEDC
Date: 2011
Abstract: A nonlinear system identification technique exploiting the dynamic response features of fully nonlinear physics-based plate models extracted by Higher-Order Spectral (HOS) analysis tools is developed. The changes induced by an imperfection in the dynamics through the structural nonlinearities are used as key detection mechanism. The differences in dynamic response of a baseline and a modified/imperfect structure are enhanced by the local nonlinearities induced by the structural modification which thus represent the specific objective of identification. The validation of the procedure and the developed algorithms is carried out through extensive experimental testing employing various plates, including isotropic and composite lay-ups, and excitation sources, including White Gaussian Noise and a train of impulses.
Publisher: Elsevier BV
Date: 11-2008
Publisher: American Institute of Aeronautics and Astronautics
Date: 20-06-2022
DOI: 10.2514/6.2022-3805
Publisher: SPIE
Date: 27-03-2008
DOI: 10.1117/12.776495
Publisher: American Institute of Aeronautics and Astronautics
Date: 23-04-2012
DOI: 10.2514/6.2012-1416
Publisher: Springer Science and Business Media LLC
Date: 11-11-2010
Publisher: American Society of Civil Engineers (ASCE)
Date: 07-2015
Publisher: Elsevier BV
Date: 10-2014
DOI: 10.5094/APR.2014.090
Publisher: American Institute of Aeronautics and Astronautics
Date: 06-01-2019
DOI: 10.2514/6.2019-1755
Publisher: Elsevier BV
Date: 07-2018
Publisher: American Society of Civil Engineers (ASCE)
Date: 11-2019
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-01-2017
DOI: 10.2514/6.2017-0638
Publisher: Elsevier BV
Date: 2001
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 2009
DOI: 10.2514/1.36071
Publisher: SAGE Publications
Date: 03-2007
Abstract: By using a combined analytical-computational methodology, a unified modelling of aerodynamic indicial functions covering the incompressible, subsonic compressible, transonic, and supersonic flight speed regimes is presented. The procedure is carried out in conjunction with a computational fluid dynamic analysis. For a plunging-pitching airfoil, selected unsteady aerodynamic load expressions have been supplied, and appropriate procedures enabling one to obtain these loads via the indicial function approach have been presented. While a single indicial function is needed to describe the aerodynamic loads in the incompressible flight speed regime, for cases where the compressibility effects play a dominant role, four indicial functions are needed. Having in view the usefulness of indicial functions towards determination of unsteady aerodynamics loads in both time and frequency domains, and implicitly for aeroelastic response and flutter predictions, the advantages of their implementation and use appear evident. Comparisons and validations of the aerodynamic model against numerical, analytical, and experimental results are presented, and pertinent conclusions are drawn.
Publisher: Elsevier BV
Date: 03-2003
Publisher: ASMEDC
Date: 2011
Abstract: Many mechanisms exist for folding and deploying wing surfaces on micro-scale unmanned air vehicles. A rolling tape-spring style wing offers simple construction, small mass, and compact packed volume. Deployment of the wing during flight would be advantageous for autonomous MAV launch, however the deployment process presents potential buckling issues due to the deployment dynamics and aero-structure interaction. In this study a finite element model of an ex le wing is developed and its deployment dynamics are compared against an experimental model. Additionally, elastic material properties are estimated using model updating, comparing predicted natural frequencies to those measured by a laser vibrometer experimentally. To better evaluate the deployment dynamics of the finite element model, in experiment a vacuum chamber is used to decouple the aero and structural dynamics. The computational results are compared with the experimental finding and good agreement was observed.
Publisher: Elsevier BV
Date: 12-2018
Publisher: American Institute of Aeronautics and Astronautics
Date: 10-01-2014
DOI: 10.2514/6.2014-0333
Publisher: Springer Science and Business Media LLC
Date: 04-2010
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-01-2020
DOI: 10.2514/6.2020-1988
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 03-2003
DOI: 10.2514/2.3950
Publisher: Elsevier BV
Date: 09-2017
Publisher: American Society of Mechanical Engineers
Date: 12-08-2012
Abstract: A parametric one-dimensional model of suspension bridges is employed to investigate their static and dynamic aeroelastic behavior in response to a gust load and at the onset of flutter. The equilibrium equations are obtained via a direct total Lagrangian formulation where the kinematics for the deck, assumed to be linear, feature the vertical and the chord-wise displacements of the deck mean axis and the torsional rotations of the deck cross sections, while preserving their shape during rotation. The cables elasto-geometric stiffness contribution is obtained by condensing the equilibrium in the longitudinal direction assuming small horizontal displacements and neglecting the cable kinematics along the bridge chord-wise direction. The equations of motion are linearized about the prestressed static aeroelastic configuration and are obtained via an updated Lagrangian formulation. The equations of motion governing the structural dynamics of the bridge are coupled with the incompressible unsteady aero-dynamic model obtained by a set of reduced-order indicial functions developed for the cross section of a suspension bridge, here represented by a rectangular cross-section. The space dependence of the governing equations is treated using the Galerkin approach borrowing as set of trial functions, the eigenbasis of the modal space. The time integration is subsequently performed by using a numerical scheme that includes the modal reduced dynamic aeroelastic Ordinary Differential Equations (ODEs) and the added aerodynamic states also represented in ODE form, the latter being associated with the lag-state formulation pertinent to the unsteady wind-induced loads. The model is suitable to analyze the effect of a time and space non uniform gust load distributed on the bridge span. The obtained aeroelastic system is also suitable to study the onset of flutter and to investigate the sensitivity of the flutter condition on geometrical and aerodynamic parameters. The flutter instability is evaluated using appropriate frequency and time domain characteristics. The parametric continuum model is exploited to perform dynamic aeroelastic flutter analysis and gust response of the Runyang Suspension Bridge over the Yangtze river in China.
Publisher: ASMEDC
Date: 2005
Abstract: This paper is concerned with the linear/nonlinear aeroelastic control of 2-D supersonic lifting surfaces. Its goal is to provide the feedback control mechanism enabling one to enlarge the flight envelope by increasing the flutter speed, and also to control the character, benign/catastrophic of the flutter instability boundary. Structural and aerodynamic nonlinearities are included in the aeroelastic governing equations, and linear and nonlinear feedback controls in both plunging and pitching are employed in conjunction with proportional velocity feedback controls. The attention of the paper is focused on multiple Hopf bifurcations. In particular, the jumping phenomenon found in our previous work will be further investigated to reveal the physical implications. It is found that such a jumping occurs when the system has multiple families of limit cycles bifurcating from a same set of parameter values with multiple solutions for frequencies. The case investigated in this paper is restricted to zero structure d ing. Center manifold reduction and normal form theory are applied to consider the stability of post-flutter solutions and the associated jumping phenomenon. Numerical simulations are presented to show the implications of time delay in the considered controls.
Publisher: ASME International
Date: 05-09-2018
DOI: 10.1115/1.4040981
Abstract: This paper presents an adaptive and computationally efficient curvature-guided algorithm for localizing optimum knot locations in fitted splines based on the local minimization of an objective error function. Curvature information is used to narrow the searching area down to a data subset where the local error function becomes one-dimensional, convex, and bounded, thus guaranteeing a fast numerical solution. Unlike standard curvature-guided methods, typically relying on heuristic rules, the novel method here presented is based on a phenomenological approach as the error function to be minimized represents geometrical properties of the curve to be fitted, consequently reducing case-sensitivity issues and the possibility of defining spurious knots. A knot-readjustment procedure performed in the vicinity of a newly created knot has the ability of dispersing knots from otherwise highly knot-populated regions, a feature known to generate undesired local oscillations. The performance of the introduced method is tested against three other methods described in the literature, each handling the knot-placement problem via a different paradigm. The quality of the fitted splines for several datasets is compared in terms of the overall accuracy, the number of knots, and the computing efficiency. It is demonstrated that the novel algorithm leads to a significantly smaller knot vector and a much lower computing time, while preserving or improving the overall accuracy.
Publisher: AIP Publishing
Date: 10-2007
DOI: 10.1063/1.2789659
Abstract: Design and analysis of a new low-noise, fast-response, high-sensitivity, compact electrometer are described. This electrometer are battery operated and capable of measuring currents down to the femto ere level. The portable, high performance nature of the electrometer renders it applicable for deployment in compact instruments for applications such as aerosol particle counters. A parametric experimental study is conducted to determine the role of different components on the performance of the electrometer. Under an ideal configuration, the electrometer has a step-up response time of ∼3s. Experiments with the electrometer used for particle counting measurements suggest that the new electrometer has high accuracy and sensitivity in comparison to the Keithley 6514 electrometer. The response of the electrometer used in particle counting studies is consistent with that of an optical single particle counter used in comparison experiments. A d ing component introduced to reduce possible spike currents in the electrometer is also seen to reduce noise and almost have no effect on response time. The electrometer response characteristics are presented in detail.
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 07-2004
DOI: 10.2514/1.679
Publisher: IEEE
Date: 12-2011
Publisher: American Society of Civil Engineers (ASCE)
Date: 05-2016
Publisher: American Institute of Aeronautics and Astronautics
Date: 07-04-2003
DOI: 10.2514/6.2003-1733
Publisher: ASME International
Date: 25-08-2011
DOI: 10.1115/1.4004427
Abstract: This paper deals with the magnetoelastic interactions for a structure consisting of two elastic current carrying superconducting substrates, separated by a gap (vacuum). The two elastic substrates, which have no acoustic contacts, are coupled by a magnetic field generated by the deformations of the substrates. The surface magnetoelastic waves of Rayleigh type, decaying exponentially with distance from substrates surfaces, are studied. For a plane harmonic wave the dispersion equation is derived and solved to obtain the coupled wave frequencies. The magnetomechanical coupling effects are investigated in detail and simulations show that the magnetoelastic coupling effect is quite significant when the gap relative thickness is rather small. The existence of two surface gap waves with two different velocities is shown. In superconducting media the constitutive relations of magnetic field and electrical current of primary nondeformed state are given by means of London’s equations.
Publisher: Elsevier BV
Date: 03-2019
Publisher: SPIE
Date: 06-04-2007
DOI: 10.1117/12.715203
Publisher: SPIE
Date: 06-04-2007
DOI: 10.1117/12.716775
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-01-2020
DOI: 10.2514/6.2020-1519
Publisher: American Institute of Aeronautics and Astronautics
Date: 04-05-2009
DOI: 10.2514/6.2009-2404
Publisher: ASMEDC
Date: 2010
Abstract: Calcium carbonate is predominantly present in cooling tower’s water and is usually the principal cause of hard water. This paper applies the modeling technique typically used for aerosol deposition to simulate the deposition process of calcium carbonate nano- and micro-particles suspended in turbulent cooling water flows. The mean turbulent velocity field and the fluctuating velocities are determined by the k-ε and RSM turbulence models by simulating the water flow in a typical heat exchanger horizontal tube. Commercial software (ANSYS FLUENT™ 12.1.4) is used for turbulence mean flow modeling and the simulation of turbulence fluctuations is performed by stochastic models. Particle deposition velocities are obtained for the particles with diameters in the range 0.01–50 μm by the k-ε and RSM models and compared to the deposition velocities calculated from semi-empirical correlations to investigate the effect of the turbulence model on the deposition velocity. Results show that the proposed numerical model can predict deposition velocity of micro-particles in water accurately and can be useful in determining the range of particle diameters in which the highest deposition velocity occurs. However, for nano-particles, the model’s results do not agree with the correlations due to the higher lateral turbulence fluctuations calculated by ANSYS FLUENT™ code. The proposed model can be useful for predicting fouling in industrial heat exchangers, for planning operations and cleaning schedules, and proposing efficient filtering processes for lowering deposition rate and cleaning costs.
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 09-2005
DOI: 10.2514/1.14037
Publisher: American Institute of Aeronautics and Astronautics
Date: 02-01-2015
DOI: 10.2514/6.2015-1859
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 09-2004
DOI: 10.2514/1.3445
Publisher: American Institute of Aeronautics and Astronautics
Date: 02-01-2015
DOI: 10.2514/6.2015-1188
Publisher: Springer International Publishing
Date: 27-12-2017
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-01-2017
DOI: 10.2514/6.2017-0416
Publisher: SPIE
Date: 06-04-2007
DOI: 10.1117/12.715328
Publisher: American Institute of Aeronautics and Astronautics
Date: 06-01-2019
DOI: 10.2514/6.2019-1533
Publisher: Springer Science and Business Media LLC
Date: 27-07-2020
Publisher: Elsevier BV
Date: 02-2005
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 2013
DOI: 10.2514/1.C031832
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 2014
DOI: 10.2514/1.C032131
Publisher: Elsevier BV
Date: 05-2008
Publisher: Emerald
Date: 03-07-2017
Abstract: The application of reduced order models (ROMs) in the aerodynamic/aeroelastic analysis of long-span bridges, unlike the aeronautical structures, has not been extensively studied. ROMs are computationally efficient techniques, which have been widely used for predicting unsteady aerodynamic response of airfoils and wings. This paper aims to discuss the application of a reduced order computational fluid dynamics (CFD) model based on the eigensystem realization algorithm (ERA) in the aeroelastic analysis of the Great Belt Bridge (GBB). The aerodynamic impulse response of the GBB section is used to construct the aerodynamic ROM, and then the aerodynamic ROM is coupled with the reduced DOF model of the system to construct the aeroelastic ROM. Aerodynamic coefficients and flutter derivatives are evaluated and compared to those of the advanced discrete vortex method-based CFD code. Results demonstrate reasonable prediction power and high computational efficiency of the technique that can serve for preliminary aeroelastic analysis and design of long-span bridges, optimization and control purposes. The application of a system identification tool like ERA into the aeroelastic analysis of long-span bridges is performed for the first time in this work. Authors have developed their earlier work on the aerodynamic analysis of long-span bridges, published in the Journal of Bridge Engineering , by coupling the aerodynamic forces with reduced DOF of structural system. The high computational efficiency of the technique enables bridge designers to perform preliminary aeroelastic analysis of long-span bridges in less than a minute.
Publisher: World Scientific Pub Co Pte Lt
Date: 09-2006
DOI: 10.1142/S0218127406016252
Abstract: In this paper we present, the design and modeling of the novel nonlinear limiter control feedback control plant [Myneni et al., 1999 Corron et al., 2000 Corron & Pethel, 2002], applied for the first time here in an aeroelastic system, and actuated as a jet reaction torquer control of a wing with potentially chaotic dynamics. This study will provide a better understanding of the nonlinear dynamics of the open/closed-loop aeroelasticity of flexible wings with either steady or unsteady aerodynamic loads. The limiter control can be applied to either the plunging or pitching characteristic of the wing or to both of them. We show that the control can effectively suppress Limit Cycle Oscillations (LCO) and chaos well beyond the nominal flutter speed. This could lead to a practical implementation of the control mechanism on actual and future generation aircraft wings via implementation of a combination of propulsive/jet type forces, micro surface effectors and fluidic devices. Analysis of this control produced favorable results in the suppression of LCO litude and increased flutter boundaries for plunging and pitching motion. The limiting control has asymptotically zero power, and is simply implemented, making it a feasible solution to the problem of the chaotic dynamics of the oscillating airfoil.
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-01-2020
DOI: 10.2514/6.2020-1647
Publisher: The Korean Society for Aeronautical & Space Sciences
Date: 30-06-2011
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 2006
DOI: 10.2514/1.15015
Publisher: American Institute of Aeronautics and Astronautics
Date: 03-01-2022
DOI: 10.2514/6.2022-2132
Publisher: American Institute of Aeronautics and Astronautics
Date: 03-01-2022
DOI: 10.2514/6.2022-2131
Publisher: American Institute of Aeronautics and Astronautics
Date: 03-01-2022
DOI: 10.2514/6.2022-2130
Publisher: SAGE Publications
Date: 02-12-2009
Abstract: The next generation of slender, flexible aircraft wings requires extremely lightweight structures capable of carrying a considerable amount of non-structural weight. With the increased slenderness and flexibility, possible with the advent of advanced composites, these wings can exhibit aeroelastic instabilities quite different from their rigid counterparts. The design of highly flexible aircraft, such as high-altitude long endurance (HALE) configurations, must include phenomena that are not usually considered in traditional aircraft design, such that an alternative design philosophy has been proposed for this class of vehicles. The discussion in this article is restricted, among the various aeroelastic phenomena, to the flutter condition. Classical procedures usually refer to aero-structural systems where the undeformed state is taken as the reference point. This is not the case with slender wing configuration where, due to the high structural flexibility, a proper beam model, capable of describing the structural flight deflections, should be adopted. Consequently, the flutter analysis has to be performed considering the deflected state as a reference point. Herein, an approximate procedure is proposed and flutter is evaluated by means of Galerkin's approach applied to the perturbed small motions of the aero-structural system. The effect of typical parameters, including stiffness ratio, mass eccentricity, store pod, deflection litude, as well as the wing aspect ratio, are considered. For a simplified wing configuration, comparisons between analytical and experimental findings are presented along with discussions and suggestions for new design criteria.
Publisher: American Institute of Aeronautics and Astronautics
Date: 03-01-2022
DOI: 10.2514/6.2022-1956
Publisher: American Institute of Aeronautics and Astronautics
Date: 04-04-2011
DOI: 10.2514/6.2011-1916
Publisher: American Institute of Aeronautics and Astronautics
Date: 02-01-2015
DOI: 10.2514/6.2015-1851
Publisher: American Society of Mechanical Engineers
Date: 07-2012
Abstract: This paper provides aerodynamic indicial functions obtained through a discrete vortex computational fluid dynamics method for two-dimensional geometries, including two canonical sections, rectangular and elliptical shapes, and the Great Belt Bridge cross section. This methodology enables one to determine the unsteady lift and aerodynamic moment necessary in aeroelastic analysis of flexible bodies including flutter and vortex induced vibration. The predictions were obtained using an unsteady viscous flow solver, DVMFLOW, developed by COWI. The indicial functions developed have two exponential groups which parameters have been obtained using a nonlinear least square method. The numerical investigations show significant flow separation for the presented sections and an enhanced dynamic stall region at the initiation of a transient leading to higher values in the lift coefficient response. Vortex shedding frequency was also determined and the results are compared with other studies in the literature.
Publisher: American Society of Mechanical Engineers
Date: 07-2012
Abstract: Reduced order models (ROMs) are computationally efficient techniques, which have been widely used for predicting unsteady aerodynamic response of airfoils and wings. However, they have not been applied extensively to perform unsteady fluid dynamic analysis of flexible structures in civil engineering. This paper discusses the application of reduced order computational fluid dynamics (CFD) model based on the eigensystem realization algorithm (ERA) in the aerodynamic analysis of flexible structures with arbitrary shaped cross sections. As an ex le of a civil structure we examine the GBB long-span bridge for which there are published experimental data. The aerodynamic impulse responses of the GBB Bridge are used to construct the ROM, and then the aerodynamic forces due to arbitrary inputs are evaluated and compared to those of the model coupled with an advanced CFD code. Results demonstrate reasonable prediction power and high computational efficiency of the technique that can serve for preliminary design, optimization and control purposes. The methodology described in this paper has wide application in many offshore engineering problems where flexible structures interact with unsteady fluid mechanical phenomena.
Publisher: MDPI AG
Date: 10-04-2023
DOI: 10.3390/AEROSPACE10040367
Abstract: Advanced composites have a brittle nature making them highly susceptible to failure and propagation under impact loading conditions. Appropriate modeling techniques to accurately simulate these conditions are required. This study presents and examines a coupled thermo-mechanical modeling technique and its associated numerical simulations for analyzing carbon fiber-reinforced composite panels subjected to high-velocity impact. The essential numerical parameters necessary to accurately simulate the selected configuration are determined through a physical-based approach, which has not been previously reported. By following the proposed framework, the conventional trial-and-error calibration process that relies on an extensive testing c aign is minimized. A stacked shell-cohesive methodology has been applied to T800/F3900 unidirectional carbon fiber/epoxy composite panel with 16 plies in a quasi-isotropic layup configuration [(0/90/45/-45)2]s. The flat composite panel was manufactured according to ASTM D8010 standards. Both failure condition and progressive damage analysis have been explored and discussed in comparison with numerical and experimental test cases available in the open literature. Thermal effects on the mechanical performance of composite targets are also discussed based on the application of the constitutive transient thermal coupling method available in LS-DYNA®. The contact heat generated by the conversion of impact-induced damage and the kinetic energy of the projectile is also evaluated and analyzed. New observations regarding modeling techniques, energy transfer, and damage mechanisms in target plates are offered. Additionally, findings related to changes in material characteristics resulting from heat transfer are discussed.
Publisher: Elsevier BV
Date: 03-2019
Publisher: Elsevier BV
Date: 05-2022
Publisher: Elsevier BV
Date: 11-2020
Publisher: SAE International
Date: 10-11-2009
DOI: 10.4271/2009-01-3129
Publisher: ASME International
Date: 25-10-2013
DOI: 10.1115/1.4025544
Abstract: This paper describes an efficient reduced order model (ROM) applied in the aerodynamic analysis of bluff bodies. The proposed method, which is based on eigensystem realization algorithm (ERA), uses the impulse response of the system obtained by computational fluid dynamics (CFD) analysis to construct a ROM that can accurately predict the response of the system to any arbitrary input. In order to study the performance of the proposed technique, three different geometries including elliptical and rectangular sections as well as the deck cross section of Great Belt Bridge (GBB) were considered. The aerodynamic coefficients of the impulse responses of the three sections are used to construct the corresponding ROM for each section. Then, the aerodynamic coefficients from an arbitrary sinusoidal input obtained by CFD are compared with the predicted one using the ROM. The results presented illustrate the ability of the proposed technique to predict responses of the systems to arbitrary sinusoidal and other generic inputs, with significant savings in terms of CPU time when compared with most CFD codes. The methodology described in this paper has wide application in many offshore engineering problems where flexible structures interact with unsteady fluid flow, and should be useful in preliminary design, in design optimization, and in control algorithm development.
Publisher: Elsevier BV
Date: 07-2021
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 05-2002
DOI: 10.2514/2.1724
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 03-2006
DOI: 10.2514/1.14011
Publisher: American Society of Mechanical Engineers
Date: 14-11-2014
Abstract: The effectiveness of a novel actuation architecture developed to control flutter and post-flutter is investigated in this paper. To this purpose, the performance of an active control strategy in various operational conditions is experimentally examined. A physical prototype, consisting of a wing section with multiple spoilers mounted on an aeroelastic apparatus, has been designed and assembled to carry out open- and closed-loop operations. Wind tunnel aeroelastic testing are performed with a plunging and pitching apparatus specifically designed to simulating wing sections with prescribed stiffness characteristics, including torsional structural nonlinearities responsible of a stable nonlinear post-flutter limit cycle behavior. Five surface mounted spoilers located at 15% of the chord from the leading edge are used to control aeroelastic vibrations in pre- and post-flutter. The spoilers design, including selection of best size and chord position and considering the geometrical constraints, has been carried out by CFD simulation, with the objective of maximizing the aerodynamic pitching moment used to stabilize the lifting surface at the various speeds. The spoiler actuations are commanded by an active control system as to extend the flight region in the natural post-flutter condition. A simple PID algorithm is implemented to test the efficiency of the control system design to suppress flutter oscillation. A trial and error tuning of the gain has been executed on-site during the experimental c aign. Only the pitch angle is used as state feedback in the control laws to stabilize the system above the open-loop flutter velocity. Results and pertinent conclusions are outlined.
Publisher: American Institute of Aeronautics and Astronautics
Date: 22-06-2004
DOI: 10.2514/6.2004-5227
Publisher: World Scientific Pub Co Pte Lt
Date: 03-2011
DOI: 10.1142/S0218127411028738
Abstract: This paper presents the nonlinear analysis of functionally graded curved panels under high temperature supersonic gas flows. The aerothermoelastic governing equations are determined via Hamilton's variational principle. The von Karman nonlinear strain–displacement relations are used to account for large deflections. The material properties are assumed to be temperature-dependent and varying through the thickness direction according to a power law distribution in terms of the volume fractions of the constituent components. The panel is assumed to be infinitely long and simply supported. The Galerkin method is applied to convert the partial differential governing equation into a set of ordinary differential equations and the resulting system of nonlinear equations is solved through a numerical integration scheme. The effects of volume fraction index, curved panel height-rise, and aerodynamic pressure, in conjunction with the applied thermal loading, on the dynamical behavior of the panel are investigated. Regular and chaotic motions regime are determined through bifurcation analysis using Poincaré maps of maximum panel deflection, panel time history, phase-space and frequency spectra as qualitative tools, while Lyapunov's exponents and dimension are used as quantitative tools.
Publisher: MDPI AG
Date: 16-03-2020
Abstract: Aiming at the experimental test of the body freedom flutter for modern high aspect ratio flexible flying wing, this paper conducts a body freedom flutter wind tunnel test on a full-span flying wing flutter model. The research content is summarized as follows: (1) The full-span finite element model and aeroelastic model of an unmanned aerial vehicle for body freedom flutter wind tunnel test are established, and the structural dynamics and flutter characteristics of this vehicle are obtained through theoretical analysis. (2) Based on the preliminary theoretical analysis results, the design and manufacturing of this vehicle are completed, and the structural dynamic characteristics of the vehicle are identified through ground vibration test. Finally, the theoretical analysis model is updated and the corresponding flutter characteristics are obtained. (3) A novel quasi-free flying suspension system capable of releasing pitch, plunge and yaw degrees of freedom is designed and implemented in the wind tunnel flutter test. The influence of the nose mass balance on the flutter results is explored. The study shows that: (1) The test vehicle can exhibit body freedom flutter at low airspeeds, and the obtained flutter speed and d ing characteristics are favorable for conducting the body freedom flutter wind tunnel test. (2) The designed suspension system can effectively release the degrees of freedom of pitch, plunge, and yaw. The flutter speed measured in the wind tunnel test is 9.72 m/s, and the flutter frequency is 2.18 Hz, which agree well with the theoretical results (with flutter speed of 9.49 m/s and flutter frequency of 2.03 Hz). (3) With the increasing of the mass balance at the nose, critical speed of body freedom flutter rises up and the flutter frequency gradually decreases, which also agree well with corresponding theoretical results.
Publisher: Elsevier BV
Date: 05-2009
Publisher: Springer Science and Business Media LLC
Date: 14-02-2007
Publisher: Wiley
Date: 21-03-2021
DOI: 10.1002/FLD.4976
Abstract: In this work, a low‐computational cost graphics processing unit (GPU) lattice Boltzmann Method, coupled with the LES Vreman turbulence model is presented. The algorithm is capable of simulating low‐ and high‐turbulence flows. In contrast to the fractional‐step presented in the Simplified Lattice Boltzmann Method, the proposed work uses a single‐step approach, allowing faster computations of the macroscopic variables without losing any spatial accuracy. Inspired by a recently introduced directional interpolation method for the probability distribution functions, the macroscopic variables for different locations are computed separately, enabling an even further simplification of the steps needed to predict the following time‐step. Similar to the simplified lattice Boltzmann method, this work reduces the required memory allocation by storing only the macroscopic variables. Multiple benchmark cases are presented to compare with results reported in the literature. Excellent agreement with reports in the literature are obtained, while improving the overall computational performance of the algorithm.
Publisher: Elsevier BV
Date: 09-2019
Publisher: American Society of Civil Engineers (ASCE)
Date: 11-2014
Publisher: AIP Publishing
Date: 12-2022
DOI: 10.1063/5.0127270
Abstract: In this article, an efficient implementation of the graphics processing unit (GPU)-accelerated single-step and simplified lattice Boltzmann method for curved (irregular) fluid domains (ISSLBM) is presented, allowing the algorithm to predict the macroscopic flow variables in realistic scenarios, such as the wind flow influenced by complex terrains. The fluid domain is approximated and reconstructed with two- and three-dimensional non-uniform rational B-splines functions, allowing customized refinements for desired regions. The model accuracy is investigated by conducting a two-dimensional flow around a circular profile for cases with low Reynolds numbers (Re = 20 and 40). Furthermore, the model is also used to simulate a highly turbulent wind flow (Re = 10 × 106) around the Bolund hill, located in Denmark. Numerical and experimental results reported in the literature are directly compared with the results from the ISSLBM algorithm, producing results with excellent agreement in all metrics. The computational performance is also analyzed, showing that the GPU-accelerated ISSLBM is significantly faster than other simulations reported in the literature.
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 05-2007
DOI: 10.2514/1.25814
Publisher: American Institute of Aeronautics and Astronautics
Date: 23-04-2007
DOI: 10.2514/6.2007-2241
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 05-2002
DOI: 10.2514/2.1735
Publisher: ASME International
Date: 07-06-2021
DOI: 10.1115/1.4051023
Abstract: Vortex-induced vibration (VIV) is a common fluid–structure interaction phenomenon in the field of wind engineering and marine engineering. The large- litude VIV has a marked impact on the slender structure in fluids, at times even destructive. To study how the VIV can be controlled, the dynamics of a rigid cylinder attached to a rotational nonlinear energy sink (R-NES) is investigated in this paper. This is done using a two degrees-of-freedom (2DOF) Van der Pol wake oscillator model adapted to consider a coupled vibration in cross-flow and streamwise directions. The governing equation of R-NES is coupled to the wake oscillator model hence, a flow-cylinder–NES coupled system is established. While exploring the dynamics of the cylinders with different mass ratios under the action of R-NES, it was found that the R-NES delivers better performance in suppressing the VIV of a cylinder with high mass ratios than that of a low mass ratios cylinder. The effect of the distinct parameters of R-NES on VIV response was also systematically investigated in this study. The results indicate that higher mass parameter β and rotation radius r̂ can lead to improved performance, while the effect of the d ing parameter ξ is complex and appears to be linked to the mass ratio of the column structure.
Publisher: Elsevier BV
Date: 05-2022
Publisher: Elsevier BV
Date: 12-2015
Publisher: Elsevier BV
Date: 12-2015
Publisher: Informa UK Limited
Date: 16-10-2022
Publisher: IEEE
Date: 06-2018
Publisher: American Institute of Aeronautics and Astronautics
Date: 06-01-2019
DOI: 10.2514/6.2019-2096
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 07-2007
DOI: 10.2514/1.27684
Publisher: American Institute of Aeronautics and Astronautics
Date: 07-01-2018
DOI: 10.2514/6.2018-0984
Publisher: SAE International
Date: 19-08-2008
DOI: 10.4271/2008-01-2237
Publisher: ASME International
Date: 11-08-2011
DOI: 10.1115/1.4004165
Abstract: This paper describes an advanced monitoring system for fouling phenomenon in a wide range of tubular heat exchangers such as condensers and intercoolers. First, a mathematical model of fouling resistance in tubular heat exchangers is adapted. The model is based on the applied thermal power, the inside heat transfer coefficient, and geometrical characteristics of the heat exchanger under consideration. The resulting model is a function of measured quantities such as water and tube wall temperatures, fluid flow velocity, and some physical properties of the fluid flowing inside the tubes, such as viscosity, conductivity, and density. Second, an on-line fouling monitoring system was prepared, and the heat transfer resistance for selected solutions was measured in real time by this system. The effect of concentration and chemical reactions on fouling was studied experimentally using contaminants such as sodium bicarbonate, sodium chloride, calcium chloride, and a mixture of sodium bicarbonate and calcium chloride. Experimental results provide quantitative information of liquid-side fouling on heat transfer surfaces, and its effects on the thermal efficiency. Experimental data are critical for heat exchanger design and for planning operating and cleaning schedules of the heat exchanger. Uncertainty analysis shows that the experimental results are acceptable and the experimental setup is appropriate for measuring fouling resistance in industrial applications.
Publisher: American Institute of Aeronautics and Astronautics
Date: 07-01-2018
DOI: 10.2514/6.2018-0186
Publisher: SAGE Publications
Date: 03-08-2017
Abstract: In this paper, a fully adaptive control design is considered for a four-degree-of-freedom aeroelastic system that has structural nonlinearities and operates in an unsteady aerodynamic incompressible flowfield. By using the flap hinge torque of a trailing-edge flap surface in combination with a leading-edge active flap, a closed-loop controller that adapts for uncertainties in the system parameters is designed. An implicit observer is implemented in the control design to compensate for lack of measurements of the lag states that model the unsteady flow. The innovative Lyapunov-based control design procedure results in a partial-state feedback adaptive controller that is globally asymptotically stable. Numerical simulation results show the effectiveness of the control strategy comparative simulations are run to illustrate the benefit of using twin flaps as opposed to the conventional single flap control design.
Publisher: Elsevier BV
Date: 2018
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 05-2006
DOI: 10.2514/1.18182
Publisher: Springer Science and Business Media LLC
Date: 13-11-2010
Publisher: Elsevier BV
Date: 07-2007
Publisher: SAGE Publications
Date: 28-07-2016
Abstract: This article evaluates the amount of energy that can be extracted from a gust using an aeroelastic energy harvester composed of a flexible wing with attached piezoelectric elements. The harvester operates in a subcritical flow region. It is modeled as a linear Euler–Bernoulli beam sandwiched between two piezoceramics. The extended Hamilton’s principle is used to derive the harvester’s equations of motion and an eigenfunction expansion is used to form a three-degree-of-freedom reduced-order model. The degrees of freedom retained in the model are two flexural degrees for the in-plane and out-of-plane displacements, and a torsional degree for the rotational displacement. Wagner and Küssner functions are used to represent the unsteady aerodynamic and gust loading, respectively. The amount of energy extracted from the system is then compared for two different deterministic gust profiles, 1-COSINE and two sharp-edged gusts forming a square gust, for various magnitudes and durations. The results show that the harvester is able to extract more energy from the square gust profile, although for both profiles the harvester extracts more power after the gust has subsided.
Publisher: American Institute of Aeronautics and Astronautics
Date: 07-04-2008
DOI: 10.2514/6.2008-1724
Publisher: Wiley
Date: 13-05-2020
DOI: 10.1002/FLD.4848
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 04-2004
DOI: 10.2514/1.9552
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 10-2021
DOI: 10.2514/1.J060598
Publisher: Inderscience Publishers
Date: 2011
Publisher: Cambridge University Press (CUP)
Date: 10-2017
DOI: 10.1017/AER.2017.88
Abstract: Higher-Order Spectra (HOS) are used to characterise the nonlinear aeroelastic behaviour of a plunging and pitching 2-degree-of-freedom aerofoil system by diagnosing structural and/or aerodynamic nonlinearities via the nonlinear spectral content of the computed displacement signals. The nonlinear aeroelastic predictions are obtained from high-fidelity viscous fluid-structure interaction simulations. The power spectral, bi-spectral and tri-spectral densities are used to provide insight into the functional form of both freeplay and inviscid/viscous aerodynamic nonlinearities with the system displaying both low- and high- litude Limit Cycle Oscillation (LCO). It is shown that in the absence of aerodynamic nonlinearity (low- litude LCO) the system is characterised by cubic phase coupling only. Furthermore, when the litude of the oscillations becomes large, aerodynamic nonlinearities become prevalent and are characterised by quadratic phase coupling. Physical insights into the nonlinearities are provided in the form of phase-plane diagrams, pressure coefficient distributions and Mach number flowfield contours.
Publisher: ASME International
Date: 02-06-2014
DOI: 10.1115/1.4027625
Abstract: Higher-order spectral (HOS) analysis tools are employed to extract the nonlinear dynamic response features of elastic and laminated plates by using both physics-based mechanical plate models and experimental data. Bispectral and trispectral densities are computed to highlight the presence and relative importance of quadratic and cubic nonlinearities. The former are associated with the presence of asymmetry either in the excitation or in the mechanical response of predeflected plates while the latter are due to midplane stretching effects. Besides the detection of these structural nonlinearities in perfect (baseline) fully cl ed plates, the changes of such nonlinearities induced by the presence of small inertial imperfections (i.e., lumped masses) are identified and exploited to localize the imperfections. The numerical and experimental investigations are carried out both on isotropic and laminated composite plates subject to Gaussian white noise excitation. The effectiveness of the HOS-based procedure for detection of the nonlinearities is fully demonstrated for both types of plates.
Publisher: American Institute of Aeronautics and Astronautics
Date: 23-04-2007
DOI: 10.2514/6.2007-2156
Publisher: Springer Science and Business Media LLC
Date: 08-2005
Publisher: The Korean Society for Aeronautical & Space Sciences
Date: 30-09-2014
Publisher: ASMEDC
Date: 2009
Abstract: A broad reliability prediction method that can deal with complex thermo-fluidic systems is introduced. The procedure provides an engineering tool by integrating multiple computational packages to enable the simulation of a wide array of systems, especially those involving physics interactions such as fluid flow and solid medium. Computational Fluid Dynamics (CFD), Finite Element Method (FEM), Monte Carlo Simulation (MCS), and Fatigue analysis tools are integrated within this approach. CFD simulation is used to determine the heat convection terms used for the transient FEM analysis. Maximum thermal stress is provided by the FEM analysis whereby the fatigue life of the component is evaluated. Due to uncertainty of input parameters, the fatigue life will be in a Probability Density Function (PDF) form, which provides the relationship between the reliability and the service life of the system. The complete procedure is demonstrated using a cylindrical ring model, and then validated using experimental data gathered for power plant boiler pipes. The results show good agreement between the two methods.
Publisher: ASMEDC
Date: 2009
Abstract: Many engineering thermal systems involve a high degree of technical risk. Their deterioration could be induced by the flow of high temperature fluids. A high-fidelity assessment tool is presented which enables the simulation of a wide array of thermal systems. It is based on linking multiple computational tools to deal with complex thermal systems. These systems may involve fluid-structure interactions. Computational Fluid Dynamics (CFD), Finite Element Method (FEM), and Fatigue tools are integrated within this approach. The CFD part of the method is first applied to an existing model, where the internal and external heat transfer coefficients are determined, and then compared to the manually-computed coefficients. The results showed good agreement between the two methods. Next, the process is applied to a simple cylindrical ring model, where CFD simulation is first performed to determine the heat transfer parameters that are needed for the transient FEM simulation. The FEM analysis results in the maximum thermal stress whereby the fatigue life of the component is computed. Finally, the effect of varying the turbulence intensity on heat transfer coefficients, thermal stress, and fatigue life is investigated.
Publisher: American Institute of Aeronautics and Astronautics
Date: 07-01-2018
DOI: 10.2514/6.2018-0704
Publisher: ASMEDC
Date: 2008
Abstract: A general procedure for reliability prediction is introduced. The procedure is applied to a cylindrical ring and can be used for any similar thermal application. The procedure is classified as a physics-based reliability prediction method. It utilizes different computational tools such as Computational Fluid Dynamics (CFD), Finite Element Method (FEM), and Monte Carlo Simulations (MCS). The process starts with CFD simulation to find the convective terms necessary for the transient FEM thermal analysis. The transient FEM thermal analysis provides values for thermal stress. These values are used in the fatigue life analysis. The end result is the fatigue life of the component. As a result of input parameters uncertainty, the resulting life will be in the form of a Probability Density Function (PDF), which enables the calculation of the reliability of the component.
Publisher: ASMEDC
Date: 2009
Abstract: The aim of this paper is to describe a monitoring system for fouling phenomenon in tubular heat exchangers. This system is based on a physical model of the fouling resistance. A mathematical model of the fouling resistance is also developed based on applied thermal heat, the inside heat transfer coefficient and geometrical characteristics of the heat exchanger. The resulting model is a function of measured quantities such as water and tube wall temperatures, fluid flow velocities, and some physical properties of the fluid flowing inside the tubes such as viscosity, conductivity, and density. An on-line fouling evaluation system has been prepared and heat transfer resistance for selected solutions has been measured in real time by this system. Experimental results provide quantitative information of liquid-side fouling on heat transfer surfaces, and its effects on the thermal efficiency. Output data is significantly important for the design, and for formulating operating and cleaning schedules of the equipment.
Publisher: Elsevier BV
Date: 10-2014
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 09-2014
DOI: 10.2514/1.G000698
Publisher: ASMEDC
Date: 2010
Abstract: The objective of this paper is to evaluate methods to increase the efficiency of a gas turbine power plant. Advanced intercooled gas turbine power plants are quite efficient, efficiency reaching about 47%. The efficiency could be further increased by recovering wasted heat. The system under consideration includes an intercooled gas turbine. The heat is being wasted in the intercooler and a temperature drop happens at the exhaust. For the current system it will be shown that combining the gas cycle with steam cycle and removing the intercooler will increase the efficiency of the combined cycle power plant up to 60%. In combined cycles the efficiency depends greatly on the exhaust temperature of the gas turbine and the higher gas temperature leads to the higher efficiency of the steam cycle. The analysis shows that the latest gas turbines with the intercooler can be employed more efficiently in a combined cycle power application if the intercooler is removed from the system.
Publisher: ASMEDC
Date: 2008
Abstract: A method that links several commercially available tools to estimate the fatigue life of thermal systems is introduced. The procedure provides an engineering tool based on existing computational packages. It is sufficiently general that it can be used for any thermal application involving fluid flow and a solid medium. A cylindrical ring model is presented to clarify the process. Computational Fluid Dynamics (CFD) and Finite Element Modeling (FEM) tools are integrated within the proposed approach. ANSYS/CFX® and Simulation® are used for such purpose. The process starts with CFD simulation to determine the convective terms necessary for the transient FEM thermal analysis. The transient FEM thermal analysis provides maximum thermal stress values. These values are employed in the fatigue life analysis to determine the fatigue life of the component.
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 2005
DOI: 10.2514/1.4335
Publisher: Informa UK Limited
Date: 05-05-2021
Publisher: American Institute of Aeronautics and Astronautics
Date: 26-06-2010
DOI: 10.2514/6.2010-8146
Publisher: World Scientific Pub Co Pte Lt
Date: 30-06-2021
DOI: 10.1142/S021945542150142X
Abstract: To generate more power, wind turbine rotors are growing in size and consequently, wind turbine tower are becoming increasingly taller and more flexible. As a result, fluid–structure interaction (FSI) of the flexible tower caused by strong wind is a very important phenomenon, and tower vibration must be carefully considered. In this paper, the physical model of the wind turbine tower is simplified appropriately, and then a multi-body dynamics model of wind turbine tower system is established based on Transfer Matrix Method of Multibody System (MSTMM). Compared with the data from finite element model (FEM) and field tests, the simulation results show that the model has a good accuracy. By coupling the mode shapes with two degrees of freedom (2-DOF) wake oscillator model, the dynamic responses of the flexible tower are computed. The influence of various foundation stiffness and top mass on tower vibration is studied systematically using this model. The results indicate that different boundary conditions can affect the maximum litude and displacement along the axis of the tower. This work provides a reference for dynamic modeling and simulation of high-rise flexible structure, and the prediction of the maximum litude of the tower vibration, which can be used for aeroelastic control purpose.
Publisher: ASMEDC
Date: 2010
Abstract: This paper discusses an experimental study on how water quality affects the corrosion rate of Cu-Ni Alloys, such as those used within a heat exchanger system. Various types of water suitable for the heat exchanger operation have been tested to predict the duration during which corrosion would become a risk. Since corrosion is governed by electrochemistry, an electrochemical experimental setup was designed, consisting of a three-electrode electrochemical cell designed to simulate the on-site state and conditions of a 90–10 Cu-Ni tube bundle inside the heat exchanger. The working electrode in use is a 90-10 Cu-Ni Rotating Cylinder Electrode (RCE). The electrolyte solution was varied with different pH values, temperature and compositions. The corrosion rate was measured by use of the Tafel method. Experiments were performed with two solutions De-Ionized water and Tap water. Further experimentation with anti-corrosives was also performed. All measurements were produced using a G300 Gamry® Potentiostat (computer controlled) conjugated with two general purpose electrochemical softwares: Gamry Framework® and Gamry Echem Analyst®. Trends of the corrosion rate as a function of pH and temperature were analyzed. Field Emission Scanning Electron Microscope (FE-SEM) tests have also been performed to determine the products, methods and elemental effects of the corrosion. Results and discussions are provided with pertinent conclusions.
Publisher: Elsevier BV
Date: 10-2012
Publisher: American Institute of Aeronautics and Astronautics
Date: 06-01-2019
DOI: 10.2514/6.2019-0487
Publisher: American Society of Mechanical Engineers
Date: 09-11-2012
Abstract: Hybrid systems consisting of a single or multiple renewable energy generators coupled with an environmentally-friendly storage system are used in renewable power production due to wide disparity between the intermittent power generated and the power demand. These systems also have the potential to provide 24/7 power without leaving a carbon footprint in operation. Finding the optimal size of a Hybrid Renewable Energy System (HRES) with no Loss of Power Supply (LPS) is of utmost concern when considering the Levelized Cost of Energy (LCE) of the system over its lifecycle. In this study, an optimization routine employing a search algorithm is developed to find the system configuration with a minimized LCE that meets also meets zero LPS. To this end, a system model is developed by integrating basic models of the subsystems. The system model is then used to investigate two different loading cases, 1) where the demand cannot be controlled as in the case of the power demand of a residential network, and 2) where the demand can be controlled up to certain limits, as in the case of the power demand of a data center or a data center network. Various types of controllable power demands (CoD) are studied. When compared to the power demand of a residential network, results demonstrate a significant reduction in the life cycle costs for CoD conditions.
Publisher: Elsevier BV
Date: 05-2006
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-04-2013
DOI: 10.2514/6.2013-1694
Publisher: ASMEDC
Date: 2010
Abstract: The effect of surface roughness on the fouling behavior of calcium carbonate is experimentally investigated. The real operating conditions of a tubular heat exchanger are simulated by performing prolonged experiments with duration of 3 to 7 days. The solution used is a mixture of sodium bicarbonate and calcium chloride in de-ionized water with the concentration of 0.4 g/l of each. An on-line fouling evaluation system was developed such that the fouling resistance for a selected solution could be measured in real time. The experiments are repeated with the same procedure for 90/10 Cu/Ni tubes with different internal surface roughness. After the experiment the surface is analyzed by analytical microscopy to investigate the morphology of the deposit layer. Comparison of the experimental results of smooth and rough surfaces shows that a combination of aragonite and calcite polymorphs are formed on rough surface while only dendritic porous aragonite crystals are formed on smooth surface. Accordingly, the deposit layer formed on rough surface is denser and has a higher thermal resistance comparing to that formed on smooth surface. The fouling factor-time curves of smooth and rough surfaces obtained by the current experimental study agree with the results found by the analytical microscopy of the surface and show higher fouling resistances for rough surface. Experimental data is significantly important for the design, and formulating operating, and cleaning schedules of the equipment.
Publisher: SAE International
Date: 10-11-2009
DOI: 10.4271/2009-01-3166
Publisher: American Society of Mechanical Engineers
Date: 04-08-2013
Abstract: A linearized parametric continuum model of a long-span suspension bridge is coupled with a nonlinear quasi-steady aerodynamic model giving the aeroelastic partial differential equations of motion reduced to the state-space ordinary differential form by adopting the Galerkin method. Numerical time-domain simulations are performed to investigate the limit cycle oscillations occurring in the range of post-flutter wind speeds. Continuation tools are thus employed to path follow the limit cycles past the flutter speed where the Hopf bifurcation occurs. The stable post-flutter behavior, which can significantly affect the bridge by fatigue, terminate at a fold bifurcation. This result represents an important assessment of the conducted aeroelastic investigations. The stability range of the limit cycle oscillations is evaluated by carrying out sensitivity analyses with respect to the main design parameters, such as the structural d ing and the initial wind angle of attack.
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-2006
DOI: 10.2514/6.2006-1641
Publisher: Elsevier BV
Date: 04-2014
Publisher: Elsevier BV
Date: 2018
Publisher: SAGE Publications
Date: 14-09-2017
Abstract: In this paper, a robust output feedback control design is developed for suppression of aeroelastic vibration of a 2-DOF nonlinear wing section system. The aeroelastic system operates in a quasi-steady aerodynamic incompressible flowfield and is actuated using a combination of a leading-edge (LE) and a trailing-edge (TE) flap. By only utilizing measurements of pitching and plunging deflections, an innovative Lyapunov-based procedure is used to design sliding mode control inputs for the LE and TE control surface deflections. The closed-loop system is shown to have semi-global asymptotic stability even in the presence of model uncertainty and unknown external gust loading. Extensive simulation results under a variety of scenarios show the effectiveness of the control strategy.
Publisher: Acoustical Society of America (ASA)
Date: 03-2017
DOI: 10.1121/1.4978525
Abstract: In the framework of the membrane theory of cylindrical shells, the localised vibration near the shell free edge is considered. This paper presents the development leading to the dispersion equations for finite length shells and for three types of boundary conditions. Based on the attained dispersion equations the localised membrane vibration conditions are analysed and remarks are offered.
Publisher: Emerald
Date: 03-01-2017
DOI: 10.1108/AEAT-11-2014-0200
Abstract: This paper aims to describe a methodology to optimize the trajectory of unconventional airship performing a high-altitude docking manoeuvre. The trajectories are based upon Bezier curves whose control points positions are optimized through particle swarm optimization algorithm. A minimum energy strategy is implemented by considering the airship physical properties. The paper describes the mathematical model of the airships, the trajectories modelling through Bezier’s curves and the optimization framework. A series of test cases has been developed to evaluate the proposed methodology. Results obtained show that the implemented procedure is able to optimize the airship trajectories and to support their in-flight docking a strong influence of the wind speed and course on the trajectories planning is highlighted. The wind speed considered in these simulations depends only on altitude, and gusts effect has been neglected. The proposed model can support the study of unconventional airship trajectories and can be useful to evaluate best in-air docking strategies. The paper addresses the problem of trajectory optimization for a class of new air vehicles with an heuristic approach.
Publisher: Elsevier BV
Date: 2022
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 05-2011
DOI: 10.2514/1.C031080
Publisher: Elsevier BV
Date: 05-2014
Publisher: SPIE
Date: 27-03-2008
DOI: 10.1117/12.776322
Publisher: American Society of Mechanical Engineers
Date: 14-11-2014
Abstract: The lifting surfaces of next generation of flying vehicle exhibits enhanced flexibility, particularly for high aspect-ratio solutions needed for high-altitude long endurance aircrafts and for 24/7 operations. Often the wing of these vehicles is designed as slender body with an aeroelastic behavior distinctive of cantilever beam. Based on this typical assumption the governing equations of a thin-walled beam modified to account for surface mount piezoelectric elements and subjected to deterministic external gust loads have been derived and its dynamic behavior examined. This paper assesses the effectiveness of piezoelectric elements to carry out load alleviation function over the slender structure invested by atmospheric disturbances along with the evaluation of the amount of the power density harvested via a suitable electric circuit connected to the piezoelectric elements.
Publisher: Elsevier BV
Date: 05-2009
Publisher: The Korean Society for Aeronautical & Space Sciences
Date: 30-06-2012
Publisher: Informa UK Limited
Date: 22-12-2009
Publisher: Elsevier BV
Date: 2019
Publisher: American Institute of Aeronautics and Astronautics
Date: 07-01-2018
DOI: 10.2514/6.2018-1011
Publisher: Elsevier BV
Date: 10-2011
Publisher: American Society of Civil Engineers (ASCE)
Date: 09-2014
Publisher: American Society of Civil Engineers (ASCE)
Date: 2014
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2023
Publisher: SAE International
Date: 15-09-2015
DOI: 10.4271/2015-01-2571
Publisher: Elsevier BV
Date: 05-2015
Publisher: SAE International
Date: 15-09-2015
DOI: 10.4271/2015-01-2455
Publisher: SAE International
Date: 15-09-2015
DOI: 10.4271/2015-01-2453
Publisher: SAGE Publications
Date: 2008
Abstract: In the current work, the study of the aeroelastic behaviour of a wing with external store(s), such as a missile or drop fuel tank, is presented. The aeroelastic governing equations derived for a cantilever wing with coupled bending and torsion modes account for structural and aerodynamic non-linearities. Coupling terms retained in the aeroelastic governing equations are due to: (a) the non-linear beam theory, (b) the aerodynamic non-linearities of a quasi-steady model with stall, and (c) the non-linear kinematics terms of the store(s). As presented in the paper, this aircraft configuration can induce pathologies, such as store(s)-induced limit cycle oscillations (or si-LCOs), very different from the one of a clean wing configuration, and from the one obtained from the linearized form of the aeroelastic governing equations. Time domain simulation, phase portrait, and bifurcation analyses are performed for various velocities, initial conditions, and store(s)-sensitive parameters — such as store mass, number, location along the wing — to examine the dynamic aeroelastic instabilities of the system (e.g. the onset of flutter and LCO). Numerical studies indicate the presence of regions of subcritical Hopf-bifurcation, corresponding to an unstable LCO, for velocities below the linear flutter velocity.
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 03-2012
DOI: 10.2514/1.54347
Publisher: SAE International
Date: 15-09-2015
DOI: 10.4271/2015-01-2578
Publisher: SAE International
Date: 15-09-2015
DOI: 10.4271/2015-01-2577
Publisher: Elsevier BV
Date: 07-2014
Publisher: Elsevier BV
Date: 03-2002
Publisher: The Korean Society for Aeronautical & Space Sciences
Date: 30-03-2013
Publisher: Elsevier BV
Date: 2013
Publisher: SAE International
Date: 18-10-2011
DOI: 10.4271/2011-01-2721
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-04-2013
DOI: 10.2514/6.2013-1676
Publisher: Elsevier BV
Date: 11-2023
Publisher: SAE International
Date: 18-10-2011
DOI: 10.4271/2011-01-2722
Publisher: Informa UK Limited
Date: 05-2012
Publisher: American Institute of Aeronautics and Astronautics
Date: 04-04-2011
DOI: 10.2514/6.2011-1769
Publisher: SAGE Publications
Date: 06-12-2016
Abstract: This article contributes to the definition of an unconventional actuation system coupled with an adaptive control algorithm, it is intended specifically for slender/highly flexible wings flutter suppression. The design and validation process of the novel actuation architecture is presented together with the performance analysis of the post-flutter dynamics control. Robustness of the overall control architecture is verified with respect to the uncertainties deriving from the unpredictable degradation of the structural properties. The proposed actuation system is based on a row of multiple mini-spoilers, located in proximity of the leading edge and coordinated by a modified model reference adaptive control algorithm. The spoiler configuration is optimized by computational fluid dynamics numerical simulation, whereas the aerodynamic database is derived by wind tunnel tests on the prototype by means of a six-axes force balance. The resulting aeroelastic mathematical model is then used to implement and validate the adaptive control algorithm for a wide range of conditions, from on-design flutter speed and nominal structural stiffness to post-flutter speed and reduced structural stiffness. The two degree of freedom aeroelastic model is successfully controlled in all conditions. This article aims at defining a robust procedure for aeroelastic phenomena control system design, which employs a synergy of modeling, simulation, and experimental approaches. Pertinent conclusions are discussed in the final section of the article.
Publisher: Informa UK Limited
Date: 23-02-2009
Publisher: SAE International
Date: 15-09-2015
DOI: 10.4271/2015-01-2462
Publisher: ASMEDC
Date: 2002
Abstract: Two basic issues related to the open/closed loop aeroelasticity of 2-D lifting surfaces in an incompressible flow field are considered in this paper. These concern the subcritical aeroelastic response to external time-dependent excitations, and the flutter instability of actively controlled airfoils involving a delayed feedback control. Results and comparisons regarding the flutter instability obtained via the first Volterra kernel in conjunction with a frequency eigenvalue analysis are presented. In the same context, the implications of the presence of time delays in the feedback control on the instability boundary and aeroelastic response are investigated and pertinent conclusions are supplied.
Publisher: American Institute of Aeronautics and Astronautics
Date: 03-04-2000
DOI: 10.2514/6.2000-0
Publisher: SAE International
Date: 15-09-2015
DOI: 10.4271/2015-01-2460
Publisher: Cambridge University Press (CUP)
Date: 10-2009
DOI: 10.1017/S0001924000003328
Abstract: The aeroelastic modeling and flutter characteristics of a shear deformable wing/stores configuration under pull-up angular velocity is investigated. An isotropic non-uniform wing, which structural model incorporates flexibility in transverse shear and warping effects, is considered. The aeroelastic governing equations and boundary conditions are determined via Hamilton’s variational principle. In order to exactly consider the span wise location and properties of the attached stores the generalised function theory is used. The partial differential equations are transformed into a set of eigenvalue equations through the extended Galerkin’s approach. Numerical simulation highlighting the effects of the pull-up angular velocity and store parameters and configurations, such as mass ratio and their attachment locations, on the flutter speed are presented. The results of flutter analyses are validated with the published results and good agreement is observed. Furthermore, the procedure for an optimal deployment of stores is obtained for the case of the wing with four stores.
Publisher: American Institute of Aeronautics and Astronautics
Date: 19-04-2004
DOI: 10.2514/6.2004-1752
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-2006
DOI: 10.2514/6.2006-2035
Publisher: IOP Publishing
Date: 28-01-2013
Publisher: Elsevier BV
Date: 02-2017
Publisher: American Institute of Aeronautics and Astronautics
Date: 23-04-2007
DOI: 10.2514/6.2007-2208
Publisher: Springer Science and Business Media LLC
Date: 05-04-2021
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 03-2011
DOI: 10.2514/1.51403
Publisher: American Institute of Aeronautics and Astronautics
Date: 09-01-2006
DOI: 10.2514/6.2006-1062
Publisher: ASMEDC
Date: 2010
Abstract: This paper evaluates the possibility of combining an intercooled gas turbine power cycle with a steam turbine cycle and the application of the intercooler as a feed-water heater for the heat recovery steam generator. In advance gas turbines the intercooler is used to improve the overall efficiency of the simple cycle but a noticeable amount of heat is wasted to the atmosphere. However, this energy can be recovered by using the proposed method in the current study. Accordingly, a thermodynamic study is done to investigate the improvement in efficiency achieved by feed-water heating. First the effect of intercooler parameters on the outlet condition of the water is studied. The bottoming cycle is then studied in details for the effect of feed-water temperature. An estimate of the energy saving by using the proposed method will be reported. The results show that less heat input will be required for the same amount of steam generation. The current study provides a theoretical support for waste heat recovery from the intercooler.
Publisher: Elsevier BV
Date: 06-2002
Publisher: American Institute of Aeronautics and Astronautics
Date: 07-01-2018
DOI: 10.2514/6.2018-1753
Publisher: Elsevier BV
Date: 02-2014
Publisher: SAE International
Date: 17-09-2013
DOI: 10.4271/2013-01-2193
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 11-2014
DOI: 10.2514/1.C032439
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-04-2013
DOI: 10.2514/6.2013-1560
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-01-2020
DOI: 10.2514/6.2020-0702
Publisher: SAE International
Date: 15-09-2015
DOI: 10.4271/2015-01-2473
Publisher: SAE International
Date: 17-09-2013
DOI: 10.4271/2013-01-2191
Publisher: SAE International
Date: 10-11-2009
DOI: 10.4271/2009-01-3196
Publisher: SAE International
Date: 15-09-2015
DOI: 10.4271/2015-01-2471
Publisher: SAE International
Date: 17-09-2013
DOI: 10.4271/2013-01-2190
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 09-2002
DOI: 10.2514/2.3882
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 09-2002
DOI: 10.2514/2.4970
Publisher: AIP Publishing
Date: 15-05-2005
DOI: 10.1063/1.1855463
Abstract: This paper details the derivation and solution of the governing equation for linear transverse vibrations of a thin perfectly conducting rotating disk subjected to an axisymmetric in-plane magnetic field having a circumferential flux pattern. Previous works on plates and shells have hypothesized that the application of a magnetic field is capable of increasing the natural frequency of a thin conductive plate. Analytical results show a significant increase in maximum stable operating speed of a thin disk in the presence of a magnetic field. The effect is dependent on both thickness and magnetic field strength.
Publisher: MDPI AG
Date: 22-03-2023
DOI: 10.3390/S23063344
Abstract: Recent developments in Distributed Satellite Systems (DSS) have undoubtedly increased mission value due to the ability to reconfigure the spacecraft cluster/formation and incrementally add new or update older satellites in the formation. These features provide inherent benefits, such as increased mission effectiveness, multi-mission capabilities, design flexibility, and so on. Trusted Autonomous Satellite Operation (TASO) are possible owing to the predictive and reactive integrity features offered by Artificial Intelligence (AI), including both on-board satellites and in the ground control segments. To effectively monitor and manage time-critical events such as disaster relief missions, the DSS must be able to reconfigure autonomously. To achieve TASO, the DSS should have reconfiguration capability within the architecture and spacecraft should communicate with each other through an Inter-Satellite Link (ISL). Recent advances in AI, sensing, and computing technologies have resulted in the development of new promising concepts for the safe and efficient operation of the DSS. The combination of these technologies enables trusted autonomy in intelligent DSS (iDSS) operations, allowing for a more responsive and resilient approach to Space Mission Management (SMM) in terms of data collection and processing, especially when using state-of-the-art optical sensors. This research looks into the potential applications of iDSS by proposing a constellation of satellites in Low Earth Orbit (LEO) for near-real-time wildfire management. For spacecraft to continuously monitor Areas of Interest (AOI) in a dynamically changing environment, satellite missions must have extensive coverage, revisit intervals, and reconfiguration capability that iDSS can offer. Our recent work demonstrated the feasibility of AI-based data processing using state-of-the-art on-board astrionics hardware accelerators. Based on these initial results, AI-based software has been successively developed for wildfire detection on-board iDSS satellites. To demonstrate the applicability of the proposed iDSS architecture, simulation case studies are performed considering different geographic locations.
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 07-2008
DOI: 10.2514/1.35139
Publisher: American Institute of Aeronautics and Astronautics
Date: 06-01-2019
DOI: 10.2514/6.2019-2104
Publisher: American Institute of Aeronautics and Astronautics
Date: 2016
DOI: 10.2514/6.2016-1953
Publisher: American Society of Civil Engineers (ASCE)
Date: 03-2014
Publisher: SAE International
Date: 17-09-2013
DOI: 10.4271/2013-01-2189
Publisher: IEEE
Date: 2005
Publisher: Elsevier BV
Date: 11-2020
Publisher: Informa UK Limited
Date: 02-09-2013
Publisher: American Institute of Aeronautics and Astronautics
Date: 03-01-2015
DOI: 10.2514/6.2015-0246
Publisher: Springer Science and Business Media LLC
Date: 21-01-2015
Publisher: SAGE Publications
Date: 06-12-2017
Abstract: The development and accelerated use of optimization frameworks in aircraft design is a testament to their ability to identify optimal and often non-intuitive shapes as a result of multi-disciplinary design objectives. Airfoil design is a continuously revised multi-disciplinary problem, and is pivotal to illustrate the performance of optimization frameworks involving numerical simulation, flexible shape parametrization, and intelligent evolutionary algorithms. An often overlooked component of this classic problem is to consider the dynamic aeroelastic behavior under trim conditions, which can generate explicit boundaries to the flight envelope. Trim introduces a significantly strong coupling with objectives governing static performance, e.g. aerodynamic and/or structural, thereby resulting in a highly nonlinear and discontinuous design space. In this paper, a multi-objective particle swarm optimization framework for multi-disciplinary performance improvement is presented, pertaining to aerodynamic, structural and aeroelastic design criteria at trim conditions. The framework is assisted by the construction of adaptive Kriging surrogates, which is cooperatively used with the numerical solver to identify optimal solutions within a computational constraint. Designer preferences are introduced to reflect the optimal compromise between the objectives. Results of the optimization process indicate a large spread in design variable influence and interaction, and a subtle yet clear distinction between all objectives is illustrated through the catalog of final airfoil candidates obtained.
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-2006
DOI: 10.2514/6.2006-1836
Publisher: American Institute of Aeronautics and Astronautics
Date: 04-04-2011
DOI: 10.2514/6.2011-1757
Publisher: Elsevier BV
Date: 12-2018
Publisher: MDPI AG
Date: 14-02-2023
DOI: 10.3390/AEROSPACE10020176
Abstract: Space-based Earth Observation (EO) systems have undergone a continuous evolution in the twenty-first century. With the help of space-based Maritime Domain Awareness (MDA), specially Automatic Identification Systems (AIS), their applicability across the world’s waterways, among others, has grown substantially. This research work explores the potential applicability of Synthetic Aperture Radar (SAR) and Distributed Satellite Systems (DSS) for the MDA operation. A robust multi-baseline Along-Track Interferometric Synthetic Aperture Radar (AT-InSAR) Formation Flying concept is proposed to combine several along-track baseline observations effectively for single-pass interferometry. Simulation results are presented to support the feasibility of implementing this acquisition mode with autonomous orbit control, using low-thrust actuation suitable for electric propulsion. To improve repeatability, a constellation of this formation concept is also proposed to combine the benefits of the DSS. An MDA application is considered as a hypothetical mission to be solved by this combined approach.
Publisher: American Institute of Aeronautics and Astronautics
Date: 10-01-2014
DOI: 10.2514/6.2014-1196
Publisher: SAGE Publications
Date: 12-2008
Abstract: Damage detection and structural health monitoring techniques based on vibration data have seen increased attention in recent years. Among the different vibration-based methods, the ones based on random vibrations are of particularly interest, especially when they do not require measurement of the input(s). In this work, several frequency and time domain signal processing techniques are explored in their respective abilities to detect damage in a bolted composite structure. First, a joint loosening model is developed and used to simulate the dynamic response to a stationary Gaussian excitation. Informed by the model, two signal processing techniques are used to assess the connection strength. The first method relies on basic statistical properties of the measured strains and their time derivatives, while the second is based on the signal power in different frequency bands. Both approaches are then used to assess progressive bolt loosening on an experimental composite-to-metal joint. All strain response data were obtained using a fiber optic strain sensing system. Results are presented in the form of Receiver Operating Characteristic (ROC) curves, showing both Type-I and Type-II errors associated with the proposed detection schemes.
Publisher: Elsevier BV
Date: 2017
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 07-2013
DOI: 10.2514/1.59725
Publisher: American Institute of Aeronautics and Astronautics
Date: 23-04-2012
DOI: 10.2514/6.2012-1977
Publisher: Elsevier BV
Date: 03-2023
Publisher: American Institute of Aeronautics and Astronautics
Date: 02-01-2015
DOI: 10.2514/6.2015-1000
Publisher: MDPI AG
Date: 26-01-2023
DOI: 10.3390/RS15030720
Abstract: One of the United Nations (UN) Sustainable Development Goals is climate action (SDG-13), and wildfire is among the catastrophic events that both impact climate change and are aggravated by it. In Australia and other countries, large-scale wildfires have dramatically grown in frequency and size in recent years. These fires threaten the world’s forests and urban woods, cause enormous environmental and property damage, and quite often result in fatalities. As a result of their increasing frequency, there is an ongoing debate over how to handle catastrophic wildfires and mitigate their social, economic, and environmental repercussions. Effective prevention, early warning, and response strategies must be well-planned and carefully coordinated to minimise harmful consequences to people and the environment. Rapid advancements in remote sensing technologies such as ground-based, aerial surveillance vehicle-based, and satellite-based systems have been used for efficient wildfire surveillance. This study focuses on the application of space-borne technology for very accurate fire detection under challenging conditions. Due to the significant advances in artificial intelligence (AI) techniques in recent years, numerous studies have previously been conducted to examine how AI might be applied in various situations. As a result of its special physical and operational requirements, spaceflight has emerged as one of the most challenging application fields. This work contains a feasibility study as well as a model and scenario prototype for a satellite AI system. With the intention of swiftly generating alerts and enabling immediate actions, the detection of wildfires has been studied with reference to the Australian events that occurred in December 2019. Convolutional neural networks (CNNs) were developed, trained, and used from the ground up to detect wildfires while also adjusting their complexity to meet onboard implementation requirements for trusted autonomous satellite operations (TASO). The capability of a 1-dimensional convolution neural network (1-DCNN) to classify wildfires is demonstrated in this research and the results are assessed against those reported in the literature. In order to enable autonomous onboard data processing, various hardware accelerators were considered and evaluated for onboard implementation. The trained model was then implemented in the following: Intel Movidius NCS-2 and Nvidia Jetson Nano and Nvidia Jetson TX2. Using the selected onboard hardware, the developed model was then put into practice and analysis was carried out. The results were positive and in favour of using the technology that has been proposed for onboard data processing to enable TASO on future missions. The findings indicate that data processing onboard can be very beneficial in disaster management and climate change mitigation by facilitating the generation of timely alerts for users and by enabling rapid and appropriate responses.
Publisher: ASME International
Date: 19-05-2006
DOI: 10.1115/1.2424469
Abstract: The study of the magnetoelastic vibrations of a flat plate immersed in a uniform applied external magnetic field is presented. Kirchhoff’s plate theory and the model of a perfect conductive medium are used. The conditions for the existence of localized bending vibrations in the vicinity of the free edge of the plate are established. It is shown that the localized vibrations can be detected and eventually can be eliminated by means of an applied magnetic field.
Publisher: SAE International
Date: 18-10-2011
DOI: 10.4271/2011-01-2648
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 02-2015
DOI: 10.2514/1.G000707
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 11-2013
DOI: 10.2514/1.61132
Publisher: SAE International
Date: 19-09-2017
DOI: 10.4271/2017-01-2061
Publisher: American Institute of Aeronautics and Astronautics
Date: 05-2006
DOI: 10.2514/6.2006-2110
Publisher: MDPI AG
Date: 11-01-2023
DOI: 10.3390/APP13021004
Abstract: Numerical simulations have the potential to be used for designing damage-tolerance composite structures. However, numerical models are currently computationally intensive, and their post-failure evolution and fracture morphology predictions are still limited. In the present work, a numerical methodology to simulate advanced composite joints is presented. The results of a numerical c aign aimed to evaluate the progressive damage and failure analysis (PDFA) of an advanced pin-hole connection under tensile and compressive load are evaluated. A high-fidelity stacked shell-cohesive methodology is employed to simulate the ultimate load, fracture initiation, and propagation of the proposed composite joint. Post-failure erosion methodology is proposed to control the initiation and evolution of composite fractures. The location and extension of the numerically predicted damages are compared with experimental observations. The proposed methodology demonstrates its preliminary ability to be used for designing composite joints up to failure. Specific outcomes are also pointed out.
Publisher: MDPI AG
Date: 19-09-2022
DOI: 10.3390/S22187070
Abstract: In recent decades, the increased use of sensor technologies, as well as the increase in digitalisation of aircraft sustainment and operations, have enabled capabilities to detect, diagnose, and predict the health of aircraft structures, systems, and components. Predictive maintenance and closely related concepts, such as prognostics and health management (PHM) have attracted increasing attention from a research perspective, encompassing a growing range of original research papers as well as review papers. When considering the latter, several limitations remain, including a lack of research methodology definition, and a lack of review papers on predictive maintenance which focus on military applications within a defence context. This review paper aims to address these gaps by providing a systematic two-stage review of predictive maintenance focused on a defence domain context, with particular focus on the operations and sustainment of fixed-wing defence aircraft. While defence aircraft share similarities with civil aviation platforms, defence aircraft exhibit significant variation in operations and environment and have different performance objectives and constraints. The review utilises a systematic methodology incorporating bibliometric analysis of the considered domain, as well as text processing and clustering of a set of aligned review papers to position the core topics for subsequent discussion. This discussion highlights state-of-the-art applications and associated success factors in predictive maintenance and decision support, followed by an identification of practical and research challenges. The scope is primarily confined to fixed-wing defence aircraft, including legacy and emerging aircraft platforms. It highlights that challenges in predictive maintenance and PHM for researchers and practitioners alike do not necessarily revolve solely on what can be monitored, but also covers how robust decisions can be made with the quality of data available.
Publisher: American Institute of Aeronautics and Astronautics
Date: 18-04-2005
DOI: 10.2514/6.2005-2256
Publisher: SAE International
Date: 17-09-2013
DOI: 10.4271/2013-01-2158
Publisher: IOP Publishing
Date: 14-06-2013
Publisher: American Meteorological Society
Date: 05-2014
Publisher: American Society of Civil Engineers (ASCE)
Date: 07-2011
Publisher: American Institute of Aeronautics and Astronautics
Date: 18-04-2005
DOI: 10.2514/6.2005-2375
Publisher: American Institute of Aeronautics and Astronautics
Date: 07-04-2003
DOI: 10.2514/6.2003-1414
Publisher: ASMEDC
Date: 2010
Abstract: The fouling effect of seawater on a 90/10 Cu/Ni commercial heat exchanger tube is investigated. A fouling monitoring device, designed on the basis of fouling thermal resistance, is used for the current experimental study. First, the seawater s les collected in different times from H ton, Rye, and Wallis beaches in New H shire, USA are vacuum-filtered down to a 10 μm filter paper to remove suspended solids, micro-organisms, and the majority of biological spores. Then, the filtered seawater s les are circulated through the closed loop experimental setup for two weeks and the fouling thermal resistance is measured continuously. The results show different fouling behavior for the seawater s les confirmed by the different composition of the s les. Analytical microscopy is performed on the tube surface before and after the experiments to see the effect of seawater fouling on the tube surface. The results of fouling monitoring experiments reveal a higher fouling thermal resistance for one of the seawater s les, H ton seawater, contrary to the results of SEM\\EDS analysis which show lower crystallization for H ton s le. Water decomposition analysis shows the lowest sodium content for H ton seawater compared to the other s les. Accordingly, accelerated corrosion of the tube surface occurs for H ton seawater due to the presence of chlorine ions and low concentration of sodium. The high fouling resistance of H ton seawater can be explained by participation of several fouling mechanisms simultaneously which makes a composite fouling behavior for H ton seawater s le. The results of the current study are critical for the industries which use seawater as the cooling water source.
Publisher: ASME International
Date: 21-11-2005
DOI: 10.1115/1.2165242
Abstract: Localized bending waves in a thin elastic orthotropic cantilever plate reinforced by a rigid rib are studied. A condition under which the edge waves can be eliminated is determined. The condition requires that the rib have a certain minimal stiffness. Such waves are time-varying, and have spatially nonuniform bending perturbations that are localized in the proximity of free surface and are quickly decaying to zero. A general solution is presented and the particular case of an isotropic reinforced plate is shown. An inverse method is described for identifying the elastic properties of the rib.
Publisher: Springer Science and Business Media LLC
Date: 07-06-2018
Publisher: ASME International
Date: 30-06-2016
DOI: 10.1115/1.4030040
Abstract: The limit cycle oscillations (LCOs) exhibited by long-span suspension bridges in post-flutter condition are investigated. A parametric dynamic model of prestressed long-span suspension bridges is coupled with a nonlinear quasi-steady aerodynamic formulation to obtain the governing aeroelastic partial differential equations adopted herewith. By employing the Faedo–Galerkin method, the aeroelastic nonlinear equations are reduced to their state-space ordinary differential form. Convergence analysis for the reduction process is first carried out and time-domain simulations are performed to investigate LCOs while continuation tools are employed to path follow the post-critical LCOs. A supercritical Hopf bifurcation behavior, confirmed by a stable LCO, is found past the critical flutter condition. The analysis shows that the LCO litude increases with the wind speed up to a secondary critical speed where it terminates with a fold bifurcation. The stability of the LCOs within the range bracketed by the Hopf and fold bifurcations is evaluated by performing parametric analyses regarding the main design parameters that can be affected by uncertainties, primarily the structural d ing and the initial wind angle of attack.
Publisher: American Institute of Aeronautics and Astronautics
Date: 18-04-2005
DOI: 10.2514/6.2005-2227
Publisher: American Society of Civil Engineers (ASCE)
Date: 09-2014
Publisher: American Institute of Aeronautics and Astronautics
Date: 11-06-2001
DOI: 10.2514/6.2001-1459
Publisher: Elsevier BV
Date: 05-2005
Publisher: American Institute of Aeronautics and Astronautics
Date: 06-01-2019
DOI: 10.2514/6.2019-0763
Publisher: SAE International
Date: 17-09-2013
DOI: 10.4271/2013-01-2265
Publisher: American Institute of Aeronautics and Astronautics
Date: 07-04-2003
DOI: 10.2514/6.2003-1867
Publisher: American Society of Mechanical Engineers
Date: 14-11-2014
Abstract: Micro-Air-Vehicles (MAV) flight regimes differs significantly from larger scales airplanes. They are operating at low Reynolds numbers of approximate 104, cruising at speed about 12m/s, and are capable of agile maneuvers in limited space environment. They are compact and easily stowable to facilitate transportation. However, due to the small size, they are usually more vulnerable to the wind gusts with significant complexities associated to their flight mechanics, stability and control, which also makes difficult to quantify flight qualities and performances. Furthermore, complex aerodynamics can produce loading scenarios leading to the destruction of the vehicle during flight operation. To minimize the size of the MAV when not in use, their wings are stowed within the body of the vehicle, and are deployed during operation. To supplement the bulk of knowledge in MAV aero-mechanics, the study of the aerodynamic characteristics of a deformable membrane MAV wing is carried out in this paper. The analysis of the membrane airfoil is performed using a fluid-structure interaction 2D model, to select a set of optimal airfoil parameters for the intended flight regime. Numerical simulations are supplied and validated with an M AV model tested in the wind tunnel.
Publisher: SAE International
Date: 17-09-2013
DOI: 10.4271/2013-01-2263
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 11-2006
DOI: 10.2514/1.19532
Publisher: ASME International
Date: 12-11-2008
DOI: 10.1115/1.3005573
Abstract: This work investigates the behavior of an electroconductive plate under the action of a nonconservative load and subjected to a transversal magnetic field. The governing equation of the bending vibrations of an electroconductive plate, subjected to a transverse magnetic field and a follower type force at one edge, is presented. The assumption of an elongated plate leads to a simplified equation, which is conveniently written in dimensionless terms. For a cantilevered configuration, the characteristic equation relative to the magnetoelastic modes of vibration of the system is derived. Approximate solutions based on Galerkin method and an adjoint formulation are also presented and compared with the semi-analytical results. Root loci plots are computed as a function of the proper dimensionless parameters. The behavior of the system is very similar to the one exhibited by other structures subjected to nonconservative loads when d ing is present. A relaxed definition of stability is used to regain continuity in the instability envelope.
Publisher: ASMEDC
Date: 2010
Abstract: The aim of this paper is to describe a monitoring system for fouling phenomenon in tubular heat exchangers. This system is based on a physical model of the fouling resistance. A mathematical model of the fouling resistance is developed based on the applied thermal heat, the inside heat transfer coefficient, and geometrical characteristics of the heat exchanger under consideration. The resulting model is a function of measured quantities such as water and tube wall temperatures, fluid flow velocities, and some physical properties of the fluid flowing inside the tubes such as viscosity, conductivity, and density. An on-line fouling evaluation system was prepared and the heat transfer resistance for selected solutions was measured in real time by this system. The effect of concentration and chemical reactions on fouling is studied experimentally by using different contaminants such as sodium bicarbonate, calcium chloride, and their mixture. Accelerated corrosion was observed for the calcium chloride-0.4g/l solution due to the presence of chlorine ions. This corrosion-fouling can be mitigated by adding sodium bicarbonate. However, calcium carbonate is formed as the result of the chemical reaction between calcium chloride and sodium bicarbonate which activates two other fouling categories, particulate fouling and crystallization. The inside surface of the tube is analyzed by analytical microscopy after the experiment to investigate different fouling categories. Experimental results provide quantitative information of liquid-side fouling on heat transfer surfaces, and its effects on the thermal efficiency. Experimental data is significantly important for the design, and for formulating operating, and cleaning schedules of the equipment.
Publisher: ASMEDC
Date: 2010
Abstract: The effect of geometrical features on the air-side heat transfer and friction characteristics of an industrial plain fin-and-tube heat exchanger is investigated by 3-D numerical modeling and simulations. The heat exchanger has been designed and employed as an intercooler in a gas power plant and is a large-size compact heat exchanger. Most of the available design correlations developed so far for plain fin–and–tube heat exchangers have been prepared for small-size exchangers and none of them fits completely to the current heat exchanger regarding the geometrical limitations of correlations. It is shown that neglecting these limitations and applying improper correlations may generate considerable amount of error in the design of such a large-size heat exchanger. The geometry required for numerical modeling is produced by Gambit® software and the boundary conditions are defined regarding the real operating conditions. Then, three-dimensional simulations based on the SIMPLE algorithm in laminar flow regime are performed by FLUENT™ code. The effect of fin pitch, tube pitch, and tube diameter on the thermo-hydraulic behavior of the heat exchanger is studied. Some variations in the design of the heat exchanger are suggested for optimization purposes. It is finally concluded that the current numerical model is a powerful tool to design and optimize of large-size plain fin-and-tube heat exchangers with acceptable accuracy.
Publisher: ASMEDC
Date: 2010
DOI: 10.1115/FEDSM-ICNMM2010-30378
Abstract: The flutter analysis of a swept aircraft wing-store configuration subjected to follower force and undergoing a roll maneuver is presented. Concentrated mass, follower force, and roll angular velocity terms are combined in the governing equations which are obtained using the Hamilton’s principle. The wing is modeled from a classical beam theory and incorporates bending-torsion flexibility. Heaviside and Dirac delta functions are used to consider the location and properties of the external mass and the follower force. Also, Peter’s unsteady aerodynamic pressure loadings are considered and modified to take the wing sweep angle effect into account. The Galerkin method is applied to convert the partial differential equations into a set of ordinary differential equations. Numerical simulations are validated with available published results. In addition, simulation results are presented to show the effects of the roll angular velocity, sweep angle, follower force, and engine mass and location, on the wing flutter. Results are indicative of the significant effect of the rigid body roll angular velocity and the follower force on the wing-engine dynamic stability. Furthermore, distances between the engine center of gravity and the wing elastic axis contribute considerable effects in the wing-engine flutter speed and frequency.
Publisher: Elsevier BV
Date: 10-2023
Publisher: Oxford University Press (OUP)
Date: 04-02-2019
DOI: 10.1016/J.JCDE.2019.02.001
Abstract: The paper broadly addresses how Industry 4.0 program drivers will impact maintenance in aviation. Specifically, Industry 4.0 practices most suitable to aeronautical maintenance are selected, and a detailed exposure is provided. Advantages and open issues are widely discussed and case studies dealing with realistic scenarios are illustrated to support what has been proposed by authors. The attention has been oriented towards Augmented Reality and Additive Manufacturing technologies, which can support maintenance tasks and spare parts production, respectively. The intention is to demonstrate that Augmented Reality and Additive Manufacturing are viable tools in aviation maintenance, and while a strong effort is necessary to develop an appropriate regulatory framework, mandatory before the wide-spread introduction of these technologies in the aerospace systems maintenance process, there has been a great interest and pull from the industry sector. Highlights Industry 4.0 practices most suitable to aeronautical maintenance are selected. Advantages and open issues are widely discussed and case studies are illustrated. Augmented Reality can support maintenance tasks. Additive Manufacturing can be useful to produce spare parts. A strong effort is necessary to develop an appropriate aeronautical regulatory framework.
Publisher: SAE International
Date: 17-09-2007
DOI: 10.4271/2007-01-3920
Publisher: American Institute of Aeronautics and Astronautics (AIAA)
Date: 04-2005
DOI: 10.2514/1.3634
Publisher: American Institute of Aeronautics and Astronautics
Date: 03-01-2022
DOI: 10.2514/6.2022-1755
Publisher: Elsevier BV
Date: 04-2013
Publisher: American Institute of Aeronautics and Astronautics
Date: 08-01-2001
DOI: 10.2514/6.2001-714
Publisher: The Korean Society for Aeronautical & Space Sciences
Date: 30-06-2012
Publisher: ACM
Date: 09-10-2023
Publisher: ASMEDC
Date: 2011
Abstract: Small villages in remote locations of developing countries rarely have access to electricity and are highly dependent on burning fossil fuels for energy. In an effort to provide these villages with a quality power supply and to replace their current emissions-producing energy generation, we propose a Hybrid Power System (HPS) that uses small wind turbines and solar panels for power generation. The system manages the intermittency of the renewable power by storing excess energy during periods of low user demand (such as night time) and releasing that energy at demand peaks (times when people are using demanding appliances). The proposed storage method uses electrolysis, which is the separation of water molecules into hydrogen and oxygen by excess DC currents produced by the wind and solar. The hydrogen is then compressed and stored in metal hydride tanks and when demand exceeds wind and solar generation, power is provided using a Proton Exchange Membrane Fuel Cell (PEMFC), which is highly responsive in peak demand periods compared to other types of hydrogen fuel cells. A physics-based model of the HPS is constructed in order to improve its efficiency, and statistics-based reliability models are formed to evaluate its potential for loss of load. Efficiency of a HPS can be viewed as balancing the energy production with user consumption. For this purpose, accurate models of the subsystems (wind turbines, solar panels, an electrolyzer using metal hydride tanks for hydrogen storage, fuel cell stack) are created. Realistic models of the AC loads are also required this includes models of a performance optimized data center (POD) and the power demanded by a small community. As to optimize the energy management of the entire system, a model of a main controller that utilizes closed-loop control systems to maintain power stability is designed. On the reliability side, analysis is performed to assess the system’s response to various failures over time. This work is aimed at examining the reliability of the power system not the examination of failure data in order to improve the reliability of various components. Models for testing of performance are created on a MATLAB Simulink and SimPowerSystems platform.
Publisher: Elsevier BV
Date: 03-2006
Publisher: SAE International
Date: 18-10-2011
DOI: 10.4271/2011-01-2735
Publisher: Elsevier BV
Date: 04-2020
Start Date: 2017
End Date: 2017
Funder: Australian Research Council
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