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Peer Reviewed
See detailNonlinear baroclinic instability : an approach based on Serrin's energy method
Henrotay, Pierre ULg

in Journal of the Atmospheric Sciences (1983), 40(3),

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See detailNonlinear compressibility effects in fluid-structure interaction and their implications on the air-blast loading of structures
Kambouchev, Nayden; Noels, Ludovic ULg; Radovitzky, Raúl

in Journal of Applied Physics (2006), 100(6), 063519

The impulse imparted by a blast wave to a freestanding solid plate is studied analytically and numerically focusing on the case in which nonlinear compressibility effects in the fluid are important, as is ... [more ▼]

The impulse imparted by a blast wave to a freestanding solid plate is studied analytically and numerically focusing on the case in which nonlinear compressibility effects in the fluid are important, as is the case for explosions in air. The analysis furnishes, in effect, an extension of Taylor's pioneering contribution to the understanding of the influence of fluid-structure interaction (FSI) on the blast loading of structures [The Scientific Papers of Sir Geoffrey Ingram Taylor, edited by G. K. Batchelor (Cambridge University Press, Cambridge, 1963), Vol. III, pp. 287-303] to the nonlinear range. The limiting cases of extremely heavy and extremely light plates are explored analytically for arbitrary blast intensity, from where it is concluded that a modified nondimensional parameter representing the mass of compressed fluid relative to the mass of the plate governs the FSI. The intermediate asymptotic FSI regime is studied using a numerical method based on a Lagrangian formulation of the Euler equations of compressible flow and conventional shock-capturing techniques. Based on the analytical and numerical results, an approximate formula describing the entire range of relevant FSI conditions is proposed. The main conclusion of this work is that nonlinear fluid compressibility further enhances the beneficial effects of FSI in reducing the impulse transmitted to the structure. More specifically, it is found that transmitted impulse reductions due to FSI when compared to those obtained ignoring FSI effects are more significant than in the acoustic limit. This result can be advantageously exploited in the design and optimization of structures with increased blast resistance. (c) 2006 American Institute of Physics. [less ▲]

Detailed reference viewed: 118 (5 ULg)
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See detailNonlinear Computational Homogenization Method for the Evaluation of Eddy Currents in Soft Magnetic Composites
Niyonzima, Innocent ULg; Sabariego, Ruth Vazquez; Dular, Patrick ULg et al

in Proceedings of the 19th Conference on the Computation of Electromagnetic Fields (COMPUMAG2013) (2013, July)

In this paper, a heterogeneous multiscale method (HMM) technique is applied to model the behaviour of electromagnetic fields in soft magnetic composites (SMC). Two problems are derived from the two-scale ... [more ▼]

In this paper, a heterogeneous multiscale method (HMM) technique is applied to model the behaviour of electromagnetic fields in soft magnetic composites (SMC). Two problems are derived from the two-scale homogenization theory: a macroscale problem that captures the slow variations of the overall solution, and many mesoscale problems that allow determining the constitutive laws at the macroscale. As application, an SMC core is considered. [less ▲]

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See detailNonlinear Computational Homogenization Method for the Evaluation of Eddy Currents in Soft Magnetic Composites
Niyonzima, Innocent ULg; Sabariego, Ruth Vazquez; Dular, Patrick ULg et al

in IEEE Transactions on Magnetics (2014), 50(02),

In this paper, a heterogeneous multiscale method technique is applied to model the behavior of electromagnetic fields in soft magnetic composites (SMC). Two problems are derived from the two-scale ... [more ▼]

In this paper, a heterogeneous multiscale method technique is applied to model the behavior of electromagnetic fields in soft magnetic composites (SMC). Two problems are derived from the two-scale homogenization theory: a macroscale problem that captures the slow variations of the overall solution, and many mesoscale problems that allow determining the constitutive laws at the macroscale. As application, an SMC core is considered. [less ▲]

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See detailNonlinear Drillstring Dynamics Analysis
Germay, Christophe; deWouw, Nathan Van; Nijmeijer, Henk et al

in SIAM Journal on Applied Dynamical Systems (2009), 8(2), 527--553

Detailed reference viewed: 29 (5 ULg)
See detailNonlinear Dynamic Analysis of Aerospace Structures
Kerschen, Gaëtan ULg; Noël, Jean-Philippe ULg; Renson, Ludovic ULg et al

Conference (2012, October)

Current practice in industry is to rely on linear finite element simulations. However, nonlinearity is a frequent occurrence in engineering structures. It is at the origin of rich and complex dynamical ... [more ▼]

Current practice in industry is to rely on linear finite element simulations. However, nonlinearity is a frequent occurrence in engineering structures. It is at the origin of rich and complex dynamical phenomena that cannot be observed in linear structures. Solving both the direct and inverse problems in nonlinear structural dynamics therefore warrants the development of appropriate methodologies. The focus of the presentation will first be on the inverse problem. We will describe the different steps of the nonlinear system identification process and discuss the current capabilities of existing methods. The presentation will then address the direct problem during which the identified model is used for accurately predicting the structure’s dynamic characteristics. A rigorous nonlinear extension of modal analysis will be presented, and we will show that it represents a very useful framework for understanding nonlinear dynamical phenomena and supporting design decisions. Two real-life aerospace structures will be considered for illustrating the proposed developments. [less ▲]

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See detailNonlinear dynamic analysis of an F-16 aircraft using GVT data
Noël, Jean-Philippe ULg; Renson, Ludovic ULg; Kerschen, Gaëtan ULg et al

in Proceedings of the International Forum on Aeroelasticity and Structural Dynamics (2013, June)

This paper aims at investigating the nonlinear dynamics of an F-16 aircraft, based upon sine-sweep data collected during a ground vibration test (GVT) campaign. Various analysis techniques, including the ... [more ▼]

This paper aims at investigating the nonlinear dynamics of an F-16 aircraft, based upon sine-sweep data collected during a ground vibration test (GVT) campaign. Various analysis techniques, including the mere visual inspection of the time series, the wavelet transform and the restoring force surface method, are utilised and reveal that the F-16 wing-to-payload mounting interfaces exhibit both softening and hardening nonlinearities. [less ▲]

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See detailNonlinear Dynamics and Control of Deep Drilling Systems
Detournay, Emmanuel; Denoël, Vincent ULg; van de Wouw, Nathan

Book published by College of Science and Engineering (2014)

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See detailNonlinear Dynamics Of A Drill Bit Under Percussive Activation
Depouhon, Alexandre ULg; Denoël, Vincent ULg; Detournay, Emmanuel

in Proceedings of ICTAM 2012, Beijing (2012, August)

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See detailNonlinear electromagnetic modes in astrophysical plasmas with dust distributions
Verheest, F.; Cattaert, Tom ULg

in Astronomy and Astrophysics (2004), 421(1), 17-21

A derivative nonlinear Schrodinger equation is obtained for parallel electromagnetic modes in plasmas containing polydisperse charged dust. The coefficient of the dispersive term in that equation is ... [more ▼]

A derivative nonlinear Schrodinger equation is obtained for parallel electromagnetic modes in plasmas containing polydisperse charged dust. The coefficient of the dispersive term in that equation is dominated by the dust rather than the (plasma) ions, and polydisperse dust yields a larger coefficient in absolute value than an equivalent monodisperse description. This leads to a significant broadening of the nonlinear structure due to the presence of polydisperse rather than monodisperse dust, the latter contributing in itself already to a substantial increase in the width of envelope solitons compared to dust-free plasmas. When modelling the charged dust by a power-law distribution occurring in planetary ring and other astrophysical systems, it depends very much on the power-law index whether the smaller or the larger grains are more important. For certain indices the more numerous smaller grains determine the charge and mass densities, but the larger dust dominates the linear and nonlinear dispersive effects. [less ▲]

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See detailNonlinear energy pumpin: A new paradigm for vibration isolation
Vakakis, Alexander F.; McFArland, D. Michael; Kerschen, Gaëtan ULg et al

in 3rd China-Japan US Symposium on Health Mondial and Control of Structures, Dalian, 2004 (2004)

We discuss passive nonlinear energy pumping from a linear (main) mechanical structure to a weakly coupled, local, passive nonlinear energy sink (NES). We show that the NES can be designed to effectively ... [more ▼]

We discuss passive nonlinear energy pumping from a linear (main) mechanical structure to a weakly coupled, local, passive nonlinear energy sink (NES). We show that the NES can be designed to effectively absorb vibrational energy from the main structure in a one-way, irreversible fashion. We demonstrate the occurrence of pumping cascades, where an appropriately designed NES passively extracts energy sequentially from a number of modes of the main (linear) structure, interacting individually with each mode before moving to the next. Experimental results confirm our theoretical findings. The applications of the nonlinear energy pumping phenomenon to the problem of vibration and shock isolation will be discussed. [less ▲]

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See detailNonlinear energy pumping: a new paradigm for vibration mitigation
Kerschen, Gaëtan ULg; Lee, Young-Sup; McFarland, D. M. et al

in 7ème congrès national de Mécanique Th. et App., Mons, 2006 (2006)

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See detailNOnlinear finite element approach to simulate wake-induced oscillation in transmission system
Snegovskiy, Dmitry; Lilien, Jean-Louis ULg

in Proceedings of ASME 2010 3rd Joint US-euorpean Fluids Engineering (FEDSM2010) (2010, August)

Wake-induced oscillations (WIO) in transmission line bundle conductors are simulated using finite-element nonlinear formulation. This allows obtaining the conductor oscillations in the line spans equipped ... [more ▼]

Wake-induced oscillations (WIO) in transmission line bundle conductors are simulated using finite-element nonlinear formulation. This allows obtaining the conductor oscillations in the line spans equipped either with spacers or with spacer dampers. Within this approach, the interaction of subconductors due to the wake is represented using Simpson’s aeroelastic model. A special force element is created to introduce the aerodynamic loads due to the wake. The aeroelastic properties of the wake force field are tuned to meet the wake-induced instability properties as measured by Price. Extension of the wake interaction sample onto the full line span is done taking into account the inertia-stiffness properties of the line fittings (spacer dampers). It is emphasized that in WIO the ability of spacer (spacer damper) to transfer the loads and motions plays essential role. Thus, the transfer matrix logic to simulate the spacer, established by Diana, Rawlins and other researchers, is now transferred into the finite element model of WIO. Some important structural specifics of transmission line fittings are thus highlighted by the performed simulations. All these developments are introduced into the FE package SAMCEF Mecano. Results of a series of calculations are presented to illustrate the feasibility of the established model. Comparison of FEM simulations to the benchmarking field test data is presented. [less ▲]

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See detailNonlinear generalization of Den Hartog׳s equal-peak method
Habib, Giuseppe ULg; Detroux, Thibaut ULg; Viguié, Régis et al

in Mechanical Systems & Signal Processing (2015), 52-53

This study addresses the mitigation of a nonlinear resonance of a mechanical system. In view of the narrow bandwidth of the classical linear tuned vibration absorber, a nonlinear absorber, termed the ... [more ▼]

This study addresses the mitigation of a nonlinear resonance of a mechanical system. In view of the narrow bandwidth of the classical linear tuned vibration absorber, a nonlinear absorber, termed the nonlinear tuned vibration absorber (NLTVA), is introduced in this paper. An unconventional aspect of the NLTVA is that the mathematical form of its restoring force is tailored according to the nonlinear restoring force of the primary system. The NLTVA parameters are then determined using a nonlinear generalization of Den Hartog׳s equal-peak method. The mitigation of the resonant vibrations of a Duffing oscillator is considered to illustrate the proposed developments. [less ▲]

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See detailNonlinear ground vibration identification of an F-16 aircraft - Part 1: Fast nonparametric analysis of distortions in FRF measurements
Vaes, Mark; Schoukens, Johan; Peeters, Bart et al

in Proceedings of the International Forum on Aeroelasticity and Structural Dynamics (2015, June)

Although they are generally modelled as linear systems, aircraft structures are known to be prone to nonlinear phenomena. A specific challenge encountered with fighter aircraft, besides aeroelastic ... [more ▼]

Although they are generally modelled as linear systems, aircraft structures are known to be prone to nonlinear phenomena. A specific challenge encountered with fighter aircraft, besides aeroelastic nonlinearity, is the modelling of the wing-to-payload mounting interfaces. For large amplitudes of vibration, friction and gaps may be triggered in these connections and markedly impact the dynamic behaviour of the complete structure. In this series of two papers, the nonlinear dynamics of an F-16 aircraft is investigated using rigorous methods applied to real data collected during a ground vibration test campaign. The present work focuses on the detection, qualification and quantification of nonlinear distortions affecting frequency response function (FRF) measurements. The key idea of the approach is to excite the structure using a random signal with a user-defined amplitude spectrum, where only a set of well-selected frequencies is different from zero in the band of interest. It is demonstrated that this careful choice of the input frequencies allows, without any further user interaction, to quantify the importance of odd and even nonlinear distortions in the output spectra with respect to the noise level. At high excitation amplitude, the F-16 dynamics is found to exhibit substantial odd nonlinearities and less significant, yet not negligible, even nonlinearities. [less ▲]

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See detailNonlinear ground vibration identification of an F-16 aircraft - Part 2: Understanding Nonlinear Behaviour in Aerospace Structures Using Sine-sweep Testing
Dossogne, Tilàn ULg; Noël, Jean-Philippe ULg; Grappasonni, Chiara ULg et al

in Proceedings of the International Forum on Aeroelasticity and Structural Dynamics (2015, June)

Although they are generally modelled as linear systems, aircraft structures are known to be prone to nonlinear phenomena. A specific challenge encountered with fighter aircraft, besides aeroelastic ... [more ▼]

Although they are generally modelled as linear systems, aircraft structures are known to be prone to nonlinear phenomena. A specific challenge encountered with fighter aircraft, besides aeroelastic nonlinearity, is the modelling of the wing-to-payload mounting interfaces. For large amplitudes of vibration, friction and gaps may be triggered in these connections and markedly impact the dynamic behaviour of the complete structure. In this series of two papers, the nonlinear dynamics of an F-16 aircraft is investigated using rigorous methods applied to real data collected during a ground vibration test campaign. The present work focuses on the analysis of sine-sweep measurements in order to get an insightful understanding about the nonlinear behaviour of the aircraft. To this extent, restoring force surface and wavelet transform methods are applied both on the collected GVT data and simulation results performed on a simple numerical model of the F-16 wing and its payload. [less ▲]

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See detailNonlinear guitar loudspeaker simulation
Schmitz, Thomas ULg; Embrechts, Jean-Jacques ULg

in Proceedings of the AES 134 th convention (2013, May)

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See detailNonlinear Interpolation on Manifold of Reduced Order Models in Magnetodynamic Problems
Paquay, Yannick ULg; Bruls, Olivier ULg; Geuzaine, Christophe ULg

in IEEE Transactions on Magnetics (2016), 52(3), 1-4

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See detailNonlinear Interpolation on Manifold of Reduced Order Models in Magnetodynamic Problems
Paquay, Yannick ULg; Bruls, Olivier ULg; Geuzaine, Christophe ULg

Poster (2015, June)

Proper Orthogonal Decomposition (POD) is an efficient model order reduction technique for linear problems in computational sciences, recently gaining popularity in electromagnetics. However, its ... [more ▼]

Proper Orthogonal Decomposition (POD) is an efficient model order reduction technique for linear problems in computational sciences, recently gaining popularity in electromagnetics. However, its efficiency has been shown to considerably degrade for nonlinear problems. In this paper, we propose a reduced order model for nonlinear magnetodynamic problems by combining POD with an interpolation on manifolds, which interpolates the reduced bases to efficiently construct the desired solution. [less ▲]

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Peer Reviewed
See detailNonlinear Marangoni Instability in 3D Rigid Boxes
Dauby, Pierre ULg; Lebon, Georgy ULg; Colinet, P.

in Greco, A. M.; Rionero, S. (Eds.) Supplemento ai rendiconti del Circolo matematico di Palermo « The Proceedings of the VIII International Conference on Waves and Stability in continuous Media, Palermo, Italy, oct. 9-14, 1995 », SERIE II – NUMERO 45– ANNO 1996, Palermo, Via Archirafi 34, Italy (1996)

Detailed reference viewed: 13 (0 ULg)