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ORBi Open Repository and Bibliography (313.923 recursos)

In may 2007, the ULg's Administrative Board (joined in June 2007 by the FUSAGx) decided to create an institutional repository and defined a strong institutional self-archiving policy to increase the visibility, accessibility and impact of the University's publications (Board's decision). This decision led to the official launch, in November 2008, of the ORBi platform including both the Academic Bibliography and the Institutional Repository of the Wallonia-Europe University Academy.

Engineering, computing & technology => Aerospace & aeronautics engineering

Mostrando recursos 1 - 20 de 60

  1. A combined Multiple Time Scales and Harmonic Balance approach for the transient and steady-state response of nonlinear aeroelastic systems

    Berci, Marco; Dimitriadis, Grigorios
    Peer reviewed

  2. A CubeSat for UV Astrophysics

    Desselle, Richard
    The full understanding of astrophysical sources requires access to a rather wide wavelength range: every wavelength domain provides another specific piece of information that is needed to solve the puzzle. Several important wavebands, such as the UV domain, can only be covered from space because of atmospheric absorption. This requires either large, sophisticated highly sensitive and versatile observatory satellites (such as IUE, HST, …) or much cheaper and smaller nano-satellites dedicated to a specific scientific question. In this presentation, I present the first results of a feasibility study of a 3U CubeSat for imaging photo-polarimetric observations of bright hot stars...

  3. Unsteady pressure measurement around aerodynamic bodies: Development of a calibration apparatus and wind tunnel testing

    Rigo, François
    Separated flows are complex but interesting to study because they are variable and unsteady. They are present for every bluff bodies and stalled streamlined bodies (at high angle of attack). Experimental aerodynamics is able to study these types of flow, using pressure sensors. Due to sensor size, pressure tubes are used to connect the pressure scanner to the tap (where the pressure is effectively measured). Statically, nothing is changed, but when an unsteady flow is studied, the signal measured by the sensor is perturbed by the tube. The Transfer Function of the tube has to be computed, to correct for...

  4. Vers l'identification non-linéaire des structures industrielles au moyen de sinus balayés

    Dossogne, Tilàn; Noël, Jean-Philippe; Kerschen, Gaëtan
    Les phénomènes vibratoires non-linéaires sont fréquemment rencontrés dans les structures mécaniques et aérospatiales. La division de ces structures en sous-systèmes assemblés ou l’usage de nouveaux matériaux favorisent l’apparition de mécanismes non-linéaires tels que le frottement, les impacts ou l'hystérésis. Il existe donc un besoin croissant en industrie de pouvoir détecter et identifier ces phénomènes non-linéaires sur des structures complexes et à grande échelle. L’ objectif de ce travail est d'établir une méthodologie d’identification des non-linéarités dans les structures industrielles, allant de la détection à la caractérisation et l’estimation de paramètres non-linéaires. Le processus d’identification est basé uniquement sur des mesures...

  5. Bayesian Inference on Uncertain Kinetic Parameters for the Pyrolysis of Composite Ablators

    Coheur, Joffrey; Magin, Thierry; Chatelain, Philippe; Arnst, Maarten

  6. Sensitivity Analysis and Uncertainty Quantification of Plasma Jet Instabilities in the VKI Plasmatron

    Coheur, Joffrey
    The VKI’s Plasmatron facility can reproduce the high-enthalpy gas flow encountered during the entry of a spacecraft into a planetary atmosphere and thus allows to test thermal protection materials used for the heat shield of the vehicle. However, the jet generated by the facility undergoes instability phenomena, which must be investigated for a correct characterization of the freestream flow and interpretation of the thermal response of the material under study. The overarching objective of this final-year project is to study the influence of thermodynamic and transport properties of the plasma jet on the instability features of this plasma jet in order...

  7. Nonlinear phase separation testing of an experimental wing-engine structure

    Renson, Ludovic; Noël, Jean-Philippe; Barton, David; Neild, Simon; Kerschen, Gaëtan
    Modal testing of nonlinear engineering structures is currently a research area that attracts substantial attention. Recently, a nonlinear generalisation of phase separation testing has been proposed for identifying nonlinear normal modes (NNMs) based on input and output measurements. The nonlinear phase separation (NPS) method integrates identification and continuation tools to calculate multiple NNMs from broadband data. The present contribution reports the first experimental application of the NPS method. The structure of interest is a model inspired by a wing with two engines connected by means of nonlinear pylons with softening-hardening stiffness characteristics. The frequency-energy dependences of four NNMs in the...

  8. Polynomial state-space model decoupling for the identification of hysteretic systems

    Esfahani, Alireza; Dreesen, Philippe; Tiels, Koen; Noël, Jean-Philippe; Schoukens, Johan
    Peer reviewed

  9. Polynomial nonlinear state-space modelling of vortex-induced vibrations: Black-box vs grey-box approach

    Decuyper, Jan; Noël, Jean-Philippe; De Troyer, Tim; Runacres, Marc; Schoukens, Johan
    The kinematics of oscillating bluff bodies in a fluid flow have been a hot research topic for decades. Most important are the potentially harmful vortex-induced vibrations (VIVs) where the structure is excited by alternating vortex shedding in its wake. Classical examples are the vibration of chimney stacks exposed to wind, pipelines on the sea-bed excited by the ocean currents or water tubes in heat exchangers. For these kind of fluid-structure interactions, typically an analytical solution cannot be found. Yet accurate predictions of the kinematics and the resulting dynamics are vital during for instance a design process, in monitoring applications or for...

  10. Subspace-based identification of a distributed nonlinearity in time and frequency domains

    Anastasio, Dario; Marchesiello, Stefano; Noël, Jean-Philippe; Kerschen, Gaëtan
    Nonlinear system identification has become of great interest during the last decades. However, a common and shared framework is not present yet, and the identification may be challenging, especially when real engineering structures are considered with strong nonlinearities. Subspace methods have proved to be effective when dealing with local nonlinearities, both in time domain (TNSI method) and in frequency domain (FNSI method). This study reports an improvement for both methods, as a first attempt to account for distributed nonlinearities, which is still an open question in the research community. A numerical beam under moderately large oscillations that exhibits geometric nonlinearity...

  11. Model updating of a wing-engine structure with nonlinear connections

    Song, Mingming; Renson, Ludovic; Noël, Jean-Philippe; Moaveni, Babak; Kerschen, Gaëtan
    This paper investigates the performance of a Bayesian model updating approach using nonlinear normal modes (NNMs). The proposed approach is applied to a wing-engine structure tested in the laboratory. The structure response to a broadband input excitation is measured experimentally. The structure NNMs are then extracted from the measured data by combining a frequency-domain nonlinear subspace identification method with numerical continuation technique. An initial finite element model of the wing-engine structure is built in Matlab and its linear stiffness parameters and the coefficients of the local nonlinearities are selected as the updating parameters. The joint posterior probability distribution of the...

  12. System identification of jointed structures: Nonlinear modal testing vs. State-space model identification

    Scheel, Maren; Kleyman, Gleb; Tatar, Ali; Brake, Matthew; Peter, Simon; Noël, Jean-Philippe; Allen, Matthew; Krack, Malte
    Two approaches for experimental identification of the nonlinear dynamical characteristics of jointed structures are investigated, (a) Nonlinear Modal Testing, (b) State-Space Model Identification. Both require only minimal a priori knowledge of the specimen. For method (a), the definition of nonlinear modes as periodic motions is used, in its generalized formulation recently proposed for nonconservative systems. The theoretically required negative damping compensating the frictional dissipation is experimentally realized by properly controlled excitation. This permits the extraction of modal frequencies, damping ratios and vibrational deflection shapes as a function of the vibration level. For method (b), a state-space model with multivariate polynomial...

  13. Locating nonlinearity in mechanical systems: A dynamic network perspective

    Noël, Jean-Philippe; Schoukens, Maarten; Van den Hof, Paul
    Though it is a crucial step for most identification methods in nonlinear structural dynamics, nonlinearity location is a sparsely addressed topic in the literature. In fact, locating nonlinearities in mechanical systems turns out to be a challenging problem when treated nonparametrically, that is, without fitting a model. The present contribution takes a new look at this problem by exploiting some recent developments in the identification of dynamic networks, originating from the systems and control community.

  14. Bayesian FE model updating using nonlinear normal modes: Application to a cantilever beam

    Song, Mingming; Renson, Ludovic; Noël, Jean-Philippe; Moaveni, Babak; Kerschen, Gaëtan
    This paper investigates the performance of a probabilistic finite element (FE) model updating approach using the Bayesian inference and nonlinear normal mode (NNM) error functions. The considered beam is the European COST Action F3 benchmark and its response in this study is simulated when subjected to a broadband excitation. The simulated response is then contaminated with different levels of Gaussian white noise to represent noisy measurements. The NNMs of the beam are identified from the noisy data by integrating a nonlinear subspace identification method and numerical continuation in a phase separation approach. An initial FE model of the beam is...

  15. Experimental study of isolas in nonlinear systems featuring modal interactions

    Detroux, Thibaut; Noël, Jean-Philippe; Virgin, Lawrence; Kerschen, Gaëtan
    Peer reviewed

  16. Parameter reduction in nonlinear state-space identification of hysteresis

    Esfahani, Alireza; Dreesen, Philippe; Tiels, Koen; Noël, Jean-Philippe; Schoukens, Johan
    Peer reviewed

  17. Grey-box state-space identification of nonlinear mechanical vibrations

    Noël, Jean-Philippe; Schoukens, Johan
    Peer reviewed

  18. Model reduction and frequency residuals for a robust estimation of nonlinearities in subspace identification

    De Filippis, Giovanni; Noël, Jean-Philippe; Kerschen, Gaëtan; Soria, Leonardo; Stephan, Cyrille
    Peer reviewed

  19. Improving CFD prediction of drag on Paralympic tandem athletes: influence of grid resolution and turbulence model

    Mannion, Paul; Toparlar, Yasin; Blocken, Bert; Hajdukiewicz, Magdalena; Andrianne, Thomas; Clifford
    Peer reviewed

  20. Improving CFD prediction of drag on Paralympic tandem athletes: influence of grid resolution and turbulence model

    Mannion, Paul; Toparlar, Yasin; Blocken, Bert; Hajdukiewicz, Magdalena; Andrianne, Thomas; Clifford
    Peer reviewed

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