ORBi Collection: Aerospace & aeronautics engineering
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Measuring nonlinear distortions: from test case to an F16 fighter
http://hdl.handle.net/2268/179602
Title: Measuring nonlinear distortions: from test case to an F16 fighter
<br/>
<br/>Author, coauthor: Vaes, Mark; Schoukens, Johan; Rolain, Yves; Peeters, Bart; Debille, Jan; Dossogne, Tilàn; Noël, JeanPhilippe; Grappasonni, Chiara; Kerschen, Gaëtan
<br/>
<br/>Abstract: What are the similarities and differences between the behavior of a small vibrating test system and an F16 fighter? To find it out, we compare measurements of the test system to measurements from the bolted connection of the wing and the missile of a F16 Fighter Falcon from the Belgian air force. These measurements were done during a ground vibration test (GVT) campaign. Essentially, the behavior of these systems match, even though the test system is only the heart of a selfstudy kit for nonlinear system identification and the F16 is a complex real life mechanical structure. This clearly shows the added value of an experiment driven nonlinear educational system identification package. It provides safe smallscale toy examples for handson exercises that react like real systems. We believe that this practical approach lowers the gap between learning system identification concepts and applying it on real systems.

A comparison of greybox and blackbox approaches in nonlinear statespace modelling and identification
http://hdl.handle.net/2268/179599
Title: A comparison of greybox and blackbox approaches in nonlinear statespace modelling and identification
<br/>
<br/>Author, coauthor: Noël, JeanPhilippe; Schoukens, Johan; Kerschen, Gaëtan
<br/>
<br/>Abstract: In the present contribution, it is shown that, in the case of mechanical systems where nonlinearities are physically localised, the general structure of blackbox nonlinear statespace models can be drastically simplified. A more parsimonious, greybox statespace representation is derived, which is found to be compatible with Newton's second law of dynamics. For demonstration purposes, blackbox and greybox statespace models of the Silverbox benchmark, i.e. an electrical mimicry of a singledegreeoffreedom mechanical system with cubic nonlinearity, are identified using a maximum likelihood estimator. It is found that the greybox approach allows to reduce markedly modelling errors with respect to a blackbox model with a comparable number of parameters. It is also suggested that the greater accuracy of the greybox model lends itself to the computation of reliable confidence bounds on the model parameters.

Importance of structural damping in the dynamic analysis of compliant deployable structures
http://hdl.handle.net/2268/179573
Title: Importance of structural damping in the dynamic analysis of compliant deployable structures
<br/>
<br/>Author, coauthor: Dewalque, Florence; Rochus, Pierre; Bruls, Olivier
<br/>
<br/>Abstract: Compliant mechanisms such as tape springs are often used on satellites to deploy appendices, e.g. solar panels, antennas, telescopes and solar sails. Their main advantage comes from the fact that their motion results from the elastic deformation of structural components, unlike usual hinges or prismatic joints, the motion of which is dictated by contact surfaces. No actuators or external energy sources are required and the deployment is purely passive, which appears as a decisive feature for the design of lowcost missions with small satellites or cubesats. The mechanical behaviour of a tape spring is intrinsically complex and nonlinear involving buckling, hysteresis and selflocking phenomena. Highﬁdelity mechanical models are then needed to get a detailed understanding of the deployment process, improve the design and predict the actual behaviour in the space 0g environment. In the majority of the previous works, dynamic simulations were performed without any physical representation of the structural damping. These simulations could be successfully achieved because of the presence of numerical damping in the transient solver. However, in this case, the dynamic response turns out to be quite sensitive to the amount of numerical dissipation, so that the predictive capabilities of the model are questionable. In this work based on numerical case studies, we show that the dynamic simulation of a tape spring can be made less sensitive to numerical parameters when the structural dissipation is taken into account.

New approach of calculation of dynamics of ball bearings
http://hdl.handle.net/2268/179535
Title: New approach of calculation of dynamics of ball bearings
<br/>
<br/>Author, coauthor: Bozet, JeanLuc; Servais, Christophe

La simulation thermoaéraulique du bâtiment : Validation et développement d’une approche couplée CFDMultizone pour l’étude de la modélisation du phénomène de surchauffe estivale en Belgique
http://hdl.handle.net/2268/179493
Title: La simulation thermoaéraulique du bâtiment : Validation et développement d’une approche couplée CFDMultizone pour l’étude de la modélisation du phénomène de surchauffe estivale en Belgique
<br/>
<br/>Author, coauthor: Barbason, Mathieu
<br/>
<br/>Abstract: For decades, growing interests in environmental and buildings energy performance concerns
lead architects and building engineers to develop new skills and to get used to advanced simulation
tools. Among them, Multizone models and Computational Fluid Dynamics (CFD) models
are increasingly used to solve problems of building physics.
This Thesis reports the development of a new and optimized tool based on the coupling of
these two tools and its application to a typical Belgian twostorey house. Indeed, separately, these
two tools have significant advantages and disadvantages :
• Multizone models are based on the hypothesis that the temperature is uniform in every
simulated zone which implies that they are not suited for large spaces. However, in small spaces,
Multizone models generate accurate results in a small amount of time.
• CFD models are very accurate, independently of the size of the room or the type of physical
phenomena encountered. However, it is also well known that CFD simulation are time and
resources consuming. Consequently, it is not possible to use it for a long term study.
This Thesis will first introduce these approaches and discuss their validity field. In order to
do this, a validation process has been developed to assess the ability of CFD to model accurately
physical phenomena at different study scales.
This Thesis will then discuss the coupling scheme developed in this study, based on experimental
results of a twostorey house in Belgium. Different coupling level will be studied in order
to understand deeply needs of such approach.
Eventually, it will be shown that coupling approach can drastically improve overheating prediction
for buildings even for a long term simulation. Thanks to this new tool, building actors
may design optimized cooling strategies while maximizing occupants comfort.; Les préoccupations environnementales croissantes et la question de la performance
énergétique des bâtiments entraînent, pour le secteur de la Construction, la nécessité d’employer
des outils de simulation dynamique avancés en physique du bâtiment. Parmi eux, les modèles
Multizone et les simulations CFD (Computational Fluid Dynamics) connaissent un essor rapide.
Cette thèse envisage le développement d’un outil de simulation optimisé basé sur le couplage
de ces deux approches et sa validation sur l’étude du comportement thermique d’une maison en
Belgique. En effet, séparément, ces deux outils présentent différents avantages et inconvénients.
• L’approche Multizone se base sur l’hypothèse d’uniformité de la température dans chaque
zone étudiée. Ceci implique l’inadéquation de cet outil pour les locaux de grandes dimensions.
A l’inverse, pour les autres locaux, il permet d’obtenir rapidement des résultats précis.
• L’approche CFD est très précise, quels que soient les dimensions du local ou les
phénomènes physiques rencontrés. Par contre, elle requiert des ressources temporelles et informatiques importantes. Par conséquent, cet outil n’est pas adapté aux simulations à long terme.
Cette Thèse présentera d’abord ces deux approches et leur champ d’application. A cet égard,
un processus de validation de la CFD traitant à la fois des phénomènes physiques et des échelles
de grandeur usuellement rencontrés en physique du bâtiment a dû être développé.
Cette Thèse abordera ensuite le développement de l’outil couplé, sur base de résultats
expérimentaux d’une habitation de deux étages en Belgique. Différents niveaux de couplage
seront envisagés afin de cerner les besoins d’une telle approche.
Enfin, il sera démontré que ce nouvel outil peut améliorer significativement la prédiction de
la surchauffe d’un bâtiment, même à long terme. Grâce à celuici, les acteurs concernés pourront
définir des stratégies de refroidissement optimisées tout en maximisant le confort des occupants.

Experimental Modal Identification of Mistuning in an Academic Blisk and Comparison With The Blades Geometry Variations
http://hdl.handle.net/2268/179329
Title: Experimental Modal Identification of Mistuning in an Academic Blisk and Comparison With The Blades Geometry Variations
<br/>
<br/>Author, coauthor: Nyssen, Florence; Arnst, Maarten; Golinval, JeanClaude

Modeling of Uncertainties in Bladed Disks Using a Nonparametric Approach
http://hdl.handle.net/2268/179328
Title: Modeling of Uncertainties in Bladed Disks Using a Nonparametric Approach
<br/>
<br/>Author, coauthor: Nyssen, Florence; Arnst, Maarten; Golinval, JeanClaude

Calibration of Gauges for Dynamic Strain Measurements on Compressor Bladed Disks
http://hdl.handle.net/2268/179327
Title: Calibration of Gauges for Dynamic Strain Measurements on Compressor Bladed Disks
<br/>
<br/>Author, coauthor: Beckers, Rémy; Nyssen, Florence; Benabou, Hicham; Viguié, Régis; Ligot, Jérôme; Simon, Daniel; Golinval, JeanClaude

Towards a Nonparametric Modelling of Multistage Assemblies of Mistuned Bladed Disks
http://hdl.handle.net/2268/179326
Title: Towards a Nonparametric Modelling of Multistage Assemblies of Mistuned Bladed Disks
<br/>
<br/>Author, coauthor: Nyssen, Florence; Arnst, Maarten; Golinval, JeanClaude

A study of composite laminates failure using an anisotropic gradientenhanced damage meanfield homogenization model
http://hdl.handle.net/2268/178536
Title: A study of composite laminates failure using an anisotropic gradientenhanced damage meanfield homogenization model
<br/>
<br/>Author, coauthor: Wu, Ling; Sket, Federico; MolinaAldareguia, Jon M; Makradi, Ahmed; Adam, Laurent; Doghri, Issam; Noels, Ludovic
<br/>
<br/>Abstract: The failure of carbon fiber reinforced epoxy laminates is studied using an anisotropic gradientenhanced continuum damage model embedded in a meanfield homogenization scheme.
In each ply, a homogenized material law is used to capture the intralaminar failure. The anisotropy of the homogenized material model results from the homogenization method and from the reformulation of the nonlocal continuum damage theory to account for the material anisotropy. As a result the damage propagation direction in each ply is predicted with accuracy as compared to the experimental results, while the problems of losing uniqueness and strain localization, which occur in classical finite element simulations when strain softening of materials is involved, can be avoided.
To model the delamination process, the hybrid discontinuous Galerkin/extrinsic cohesive law method is introduced at the ply interfaces. This hybrid method avoids the need to propagate topological changes in the mesh with the propagation of the delamination while it preserves the consistency and stability in the uncracked interfaces.
As a demonstration, openhole coupons with different stacking sequences are studied numerically and experimentally.
Both the intra and interlaminar failure patterns are shown to be well captured by the computational framework.

Regressionbased modelling of a fleet of gas turbine engines for performance trending
http://hdl.handle.net/2268/178530
Title: Regressionbased modelling of a fleet of gas turbine engines for performance trending
<br/>
<br/>Author, coauthor: Borguet, Sébastien; Léonard, Olivier; Dewallef, Pierre
<br/>
<br/>Abstract: Module performance analysis is a wellestablished framework
to assess changes in the health condition of the components
of the engine gaspath. The primary material of the technique is
the socalled vector of residuals, which are built as the difference
between actual measurement taken in the gaspath and values
predicted by means of an engine model. Obviously, the quality of
the assessment of the engine condition depends strongly on the
accuracy of the engine model.
The present paper proposes a new approach for datadriven
modelling of a fleet of engines of a given type. Such blackbox
models can be designed by operators such as airlines and thirdparty
companies. The fleetwide modelling process is formulated
as a regression problem that provides a dedicated model for each
engine in the fleet, while recognising that all engines are of the
same type. The methodology is applied to a virtual fleet of engines
generated within the ProDiMES environment. The set of
models is assessed quantitatively through the coefficient of determination
and is further used to perform anomaly detection.

A complete closed form vectorial solution to the Kepler problem
http://hdl.handle.net/2268/178262
Title: A complete closed form vectorial solution to the Kepler problem
<br/>
<br/>Author, coauthor: Condurache, D.; Martinusi, Vladimir
<br/>
<br/>Abstract: The paper gives an exact vectorial solution to the Kepler problem. A vectorial regularization that linearizes the Kepler problem is given using a Sundman transformation. Closed form expressions describing the Keplerian motion are deduced. A unified approach to the classic Kepler problem is offered, by studying both rectilinear and nonrectilinear Keplerian motions with the same instrument. The approach is an elementary one and only simple vectorial computations are involved. © 2007 Springer Science+Business Media B.V.

Exact solution to the relative orbital motion in a central force field
http://hdl.handle.net/2268/178261
Title: Exact solution to the relative orbital motion in a central force field
<br/>
<br/>Author, coauthor: Condurache, D.; Martinusi, Vladimir
<br/>
<br/>Abstract: The paper presents the exact solution to the relative orbital motion that takes place in a central force field.This problem is a generalization of the problem of the Keplerian relative motion in a central force field. The solution is presented in a coordinate free vectorial form, offering closed form expressions for the law of motion and the velocity. The solution is offered to the nonlinear model of the relative motion problem, and itgeneralizes the solutions found by ClohessyWiltshire, Lawden and TschaunerHempel for the case of the Keplerian relative motion. The applications of this problem are in satellite formation flying, satellite constellations and orbital rendezvous.

Analytic solution to the relative orbital motion around an oblate planet
http://hdl.handle.net/2268/178260
Title: Analytic solution to the relative orbital motion around an oblate planet
<br/>
<br/>Author, coauthor: Condurache, D.; Martinusi, Vladimir
<br/>
<br/>Abstract: The paper offers a vectorial approach to the J2perturbed relative orbital motion. The model uses mean orbital elements in order to derive closed form expressions for the relative position and relative velocity with respect to the LVLH frame attached on a main satellite. The advantage of the present approach is that only the motion of one satellite must be known, together with the initial conditions with respect to LVLH of the other satellites. As in the previous works of the authors, a tensorial instrument is used in order to transfer the motion from inertial to noninertial reference frames and back. In this way, a concise instrument for the study of the satellites formations under the influence of the oblateness factor J2 is offered. Copyright © 2009 by Daniel Condurache and Vladimir Martinusi.
<br/>
<br/>Commentary: 81960
9781563479786

Hypercomplex eccentric anomaly in the unified solution to the relative orbital motion
http://hdl.handle.net/2268/178259
Title: Hypercomplex eccentric anomaly in the unified solution to the relative orbital motion
<br/>
<br/>Author, coauthor: Condurache, D.; Martinusi, Vladimir
<br/>
<br/>Abstract: The present work offers an approach to the relative orbital motion by using hypercomplex algebra. An extension to this notion is used for vectors, by introducing the hypercomplex vector in the same way as hypercomplex numbers are defined. The solution to the relative orbital motion is offered in all possible situations (it stands for any Keplerian reference or targeted trajectories). A unified view on the relative orbital motion is suggested, by generalizing the previous approaches. The solution is offered to the nonlinear model of the relative motion and it is expressed in a coordinatefree hypercomplex vectorial closed form. The key element of this approach is the hypercomplex eccentric anomaly, introduced via a Sundmanlike vectorial regularization.
<br/>
<br/>Commentary: 86723
9780877035572

Closedform solutions for satellite relative motion in an axiallysymmetric gravitational field
http://hdl.handle.net/2268/178258
Title: Closedform solutions for satellite relative motion in an axiallysymmetric gravitational field
<br/>
<br/>Author, coauthor: Martinusi, Vladimir; Gurfil, P.
<br/>
<br/>Abstract: A different approach is proposed for the study of satellite relative motion in an axiallysymmetric gravitational field. Instead of using the Keplerian motion as the generating nominal orbit for the absolute motion, another "unperturbed" orbit is proposed instead: An equatorial orbit about an oblate planet. Based on the superintegrability of such motion, closedform solutions for the equatorial relative motion are obtained. Analytic conditions for the periodicity of the relative motion in a generic central force field are presented, and utilized to design longterm bounded relative motion under highorder even zonal perturbations.
<br/>
<br/>Commentary: 86783
9780877035695

State Space Analysis for The Relative Spacecraft Motion in Geopotential fields
http://hdl.handle.net/2268/178257
Title: State Space Analysis for The Relative Spacecraft Motion in Geopotential fields
<br/>
<br/>Author, coauthor: Condurache, Daniel; Martinusi, Vladimir
<br/>
<br/>Abstract: The paper offers an approach to the relative orbital motion from a new point of view, which introduces a unified way to approach both the relative position and the relative velocity with the help of a single appropriately defined tensor operator. In the situation of an unperturbed gravitational field, this operator is written with respect to the eccentric anomaly associated to the deputy spacecraft inertial orbit. In the situation of the relative equatorial motion around an oblate planet, the operator may be written with the help of elliptic integrals. The six dimensional curve in the state space (position and velocity) is completely described with the help of the parametrization which emerges from the present approach. The applications are in orbit initialization, rendezvous and docking maneuvers, as well as it constitutes a basis for propagating nominal integrable orbits when dealing with perturbations. © 2011 by Daniel Condurache and Vladimir Martinusi.
<br/>
<br/>Commentary: 97951
9781600869525

A closed form solution of the two body problem in noninertial reference frames
http://hdl.handle.net/2268/178254
Title: A closed form solution of the two body problem in noninertial reference frames
<br/>
<br/>Author, coauthor: Condurache, Daniel; Martinusi, Vladimir
<br/>
<br/>Abstract: A comprehensive analysis, together with the derivation of a closed form solution to the twobody problem in arbitrary noninertial reference frames are made within the present work. By using an efficient mathematical instrument, which is closely related to the attitude kinematics methods, the motion in the noninertial reference frame is completely solved. The closed form solutions for the motion in the noninertial frame, the motion of the mass center, and the relative motion are presented in the paper. Dynamical characteristics analogue to the linear momentum, angular momentum and total energy are introduced. In the general situation, these quantities may be determined as functions of time, and their derivation is presented within the paper. In the situation where the noninertial frame has only a rotation motion, these quantities become first integrals in a larger sense, with respect to an adequately defined differentiation rule.

Universal functions in the study of the relative orbital dynamics
http://hdl.handle.net/2268/178253
Title: Universal functions in the study of the relative orbital dynamics
<br/>
<br/>Author, coauthor: Condurache, Daniel; Martinusi, Vladimir
<br/>
<br/>Abstract: The closedform solution to the problem of the relative motion in gravitational fields is expressed with the help of the universal functions. The full nonlinear model of the relative motion is considered, and no linearization or approximation assumptions are made. The results are free of singularities and they hold for any reference and targeted orbits, as well as for any time scale. A unified way to propagate the relative orbit with respect to time is introduced, by making use of the solution to a generalized Kepler equation.
<br/>
<br/>Commentary: 96170
9780877035879

Analytic Models for Orbit Propagation in the Presence of Oblateness and Atmospheric Drag
http://hdl.handle.net/2268/178186
Title: Analytic Models for Orbit Propagation in the Presence of Oblateness and Atmospheric Drag
<br/>
<br/>Author, coauthor: Martinusi, Vladimir; Dell'Elce, Lamberto; Kerschen, Gaëtan