ORBi Collection: Aerospace & aeronautics engineering
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On the Use of Principal Component Analysis for Parameter Identification and Damage Detection in Structures
http://hdl.handle.net/2268/174339
Title: On the Use of Principal Component Analysis for Parameter Identification and Damage Detection in Structures
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<br/>Author, co-author: Golinval, Jean-Claude
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<br/>Abstract: Modal analysis is used extensively for understanding the dynamic behaviour of structures as well as for structural health monitoring or damage detection based on output-only measurements. In this presentation, a different approach based on principal component analysis is considered.
Principal component analysis (PCA), also called proper orthogonal decomposition (POD), is a multi-variate statistical method that aims at obtaining a compact representation of the data. In the present paper, PCA (POD) is used for three purposes, namely damage detection, structural health monitoring and identification of nonlinear parameters.
The key idea of PCA is to reduce a large number of measured data to a much smaller number of uncorrelated variables while retaining as much as possible of the variation in the original data. To this purpose, an orthogonal transformation to the basis of the eigenvectors of the sample covariance matrix is performed, and the data are projected onto the subspace spanned by the eigenvectors corresponding to the largest eigenvalues. This transformation has the property to decorrelate the signal components and to maximize variance.
The first problem to which PCA is applied here is the damage detection problem. When applied to vibration measurements, it can be shown that the basis of eigenvectors (called the proper orthogonal modes) span the same subspace as the mode-shape vectors of the monitored structure. Thus the damage detection problem may be solved using the concept of subspace angle between a reference subspace spanned by the eigenvectors of the initial (undamaged) structure and the subspace spanned by the eigenvectors of the current (possibly damaged) structure.
The second problem concerns structural health monitoring of civil engineering structures when environmental effects (e.g. the influence of the variation of the ambient temperature) have to be removed from the structural changes. In this case, PCA may be applied on identified modal features (e.g. the natural frequencies) to separate the changes due to environmental variations from the changes due to damage sources. This procedure is illustrated on the example of a real bridge located in Luxembourg.
The third problem is related to the estimation of nonlinear parameters using model updating techniques. In this case, the most interesting property of PCA is that it minimizes the average squared distance between the original signal and its reduced linear representation. When applied to nonlinear problems, PCA gives the optimal approximating linear manifold in the configuration space represented by the data. The linear nature of the method is appealing because the theory of linear operators is still available. However, it should be borne in mind that it also exhibits its major limitation when the data lie on a nonlinear manifold.Experimental demonstration of a 3D-printed nonlinear tuned vibration absorber
http://hdl.handle.net/2268/173803
Title: Experimental demonstration of a 3D-printed nonlinear tuned vibration absorber
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<br/>Author, co-author: Grappasonni, Chiara; Habib, Giuseppe; Detroux, Thibaut; Kerschen, Gaëtan
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<br/>Abstract: Engineering structures are designed to be lighter and more flexible, hence reducing the extent of application of linear dynamic models. Concurrently, vibration mitigation is required for enhancing the performance, comfort or safety in real-life applications. Passive linear vibration absorbers are purpose-built, often designed using Den Hartog's equal-peak strategy. However, nonlinear systems are known to exhibit frequency-energy-dependent oscillations which linear absorbers cannot effectively damp out. In this context, the paper introduces a new nonlinear tuned vibration absorber (NLTVA) whose nonlinear functional form is tailored according to the frequency-energy dependence of the nonlinear primary structure. The NLTVA design aims at ensuring equal peaks in the nonlinear receptance function for an as large as possible range of forcing amplitudes, hence generalizing Den Hartog's method to nonlinear systems. Our focus in this study is on experimental demonstration of the NLTVA performance using a primary structure consisting of a cantilever beam with a geometrically nonlinear component at its free end. The absorber is implemented using a doubly-clamped beam fabricated thanks to 3D printing. The NLTVA performance is also compared with that of the classical linear tuned vibration absorber.Internal Resonance and Stall-Flutter in a pitch-Flap Wing in the Wind-Tunnel
http://hdl.handle.net/2268/173641
Title: Internal Resonance and Stall-Flutter in a pitch-Flap Wing in the Wind-Tunnel
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<br/>Author, co-author: Verstraelen, Edouard; Kerschen, Gaëtan; Dimitriadis, Grigorios
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<br/>Abstract: Nonlinear aeroelastic phenomena such as store-induced LCOs, transonic buzz and stall flutter are the burden or modern aircraft: they reduce the performance and can even limit the flight envelope in both civil and military cases. Several nonlinear setups were studied experimentally in the last decades by the scientific community but most of them have pitch and plunge degrees of freedom and feature a rigid wing. In this paper, we study a new nonlinear aeroelastic apparatus that features nonlinear pitch and flap degrees of freedom, coupled with a flexible wing. The model is tested experimentally in the wind tunnel to determine its dynamic behaviour. Preliminary observations demonstrate that the system undergoes a supercritical Hopf bifurcation due to the hardening nonlinearity followed by an amplitude jump that is the consequence of either dynamic stall (i.e. stall flutter) or internal resonance (i.e. interaction between the hardening nonlinearity and higher modes).Experimental nonlinear identification of an aircraft with bolted connections
http://hdl.handle.net/2268/173585
Title: Experimental nonlinear identification of an aircraft with bolted connections
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<br/>Author, co-author: De Filippis, Giovanni; Noël, Jean-Philippe; Kerschen, Gaëtan; Soria, Leonardo; Stephan, Cyrille
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<br/>Abstract: Aircraft structures are known to be prone to nonlinear phenomena, especially as they constantly become lighter and hence more flexible. One specific challenge that is regularly encountered is the modeling of the mounting interfaces between aircraft subcomponents. Indeed, for large amplitudes of vibration, such interfaces may loosen and, in turn, trigger complex mechanisms such as friction and clearances. In this context, the present work intends to investigate the nonlinear dynamics of the Morane–Saulnier Paris aircraft, accessible at ONERA. This aircraft possesses multiple bolted connections between two external fuel tanks and wing tips. The objective of the paper is specifically to carry out an adequate identification of the numerous nonlinearities affecting the dynamics of this full-scale structure. Nonlinearity detection and the subsequent subspace-based parameter estimation have been performed on experimental data, collected during an on-ground test campaign. Nonlinearity detection is first achieved by the comparison of frequency response functions estimated at low excitation level, with those obtained at high amplitude level, yielding insight towards accurately characterizing the behavior of the bolted connections. Then, a nonlinear subspace identification method is applied to measured data to estimate the linear and nonlinear parameters of the structure and novel strategies and tools that overcome specific arisen problems are developed.Experimental modal analysis of nonlinear structures using broadband data
http://hdl.handle.net/2268/173584
Title: Experimental modal analysis of nonlinear structures using broadband data
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<br/>Author, co-author: Noël, Jean-Philippe; Renson, Ludovic; Grappasonni, Chiara; Kerschen, Gaëtan
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<br/>Abstract: The objective of the present paper is to develop a rigorous identification methodology of nonlinear normal modes (NNMs) of engineering structures. This is achieved by processing experimental measurements collected under broadband forcing. The use of such a type of forcing signal allows to excite multiple NNMs simultaneously and, in turn, to save testing time. A two-step methodology integrating nonlinear system identification and numerical continuation of periodic solutions is proposed for the extraction of the individual NNMs from broadband input and output data. It is demonstrated using a numerical cantilever beam possessing a cubic nonlinearity at its free end. The proposed methodology can be viewed as a nonlinear generalization of the phase separation techniques routinely utilized for experimental modal analysis of linear structures. The paper ends with a comparison between this new nonlinear phase separation technique and a previously-developed nonlinear phase resonance method.The Harmonic Balance Method for Bifurcation Analysis of Nonlinear Mechanical Systems
http://hdl.handle.net/2268/173556
Title: The Harmonic Balance Method for Bifurcation Analysis of Nonlinear Mechanical Systems
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<br/>Author, co-author: Detroux, Thibaut; Renson, Ludovic; Masset, Luc; Kerschen, Gaëtan
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<br/>Abstract: Because nowadays structural engineers are willing to use or at least understand nonlinearities instead of simply avoiding them, there is a need for numerical tools performing analysis of nonlinear large-scale structures. Among these techniques, the harmonic balance (HB) method is certainly one of the most commonly used to study finite element models with reasonably complex nonlinearities. However, in its classical formulation the HB method is limited to the approximation of periodic solutions. For this reason, the present paper proposes to extend the method to the detection and tracking of codimension-1 bifurcations in the system parameters space. As an application, the frequency response of a spacecraft is studied, together with two nonlinear phenomena, namely quasiperiodic oscillations and detached resonance curves. This example illustrates how bifurcation tracking using the HB method can be employed as a promising design tool for detecting and eliminating such undesired behaviors.Piezoelectric vibration damping using resonant shunt circuits: an exact solution
http://hdl.handle.net/2268/173554
Title: Piezoelectric vibration damping using resonant shunt circuits: an exact solution
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<br/>Author, co-author: Soltani, Payam; Kerschen, Gaëtan; Tondeau, Gilles; Deraemaeker, ArnaudComparison of off-axis TMA and FMA telescopes optimized over different fields of view: applications to Earth observation
http://hdl.handle.net/2268/173468
Title: Comparison of off-axis TMA and FMA telescopes optimized over different fields of view: applications to Earth observation
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<br/>Author, co-author: Clermont, Lionel; Stockman, Yvan; Dierckx, Wouter; Loicq, Jerôme
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<br/>Abstract: TMA, or three mirror anastigmats, have already been used successfully for various space missions. In the frame of earth observation, ProbaV satellite uses 3 TMAs to cover a total 102.4° field-of-view; ground sampling distance is about 100m at the center of field-of view and 370m at the edge. For future earth observation missions, the goal would be to reach 100m spatial resolution all over the 102.4° FOV. This would require to up-scale optical specifications, thus increasing geometrical aberrations. FMA, or four mirror anastigmats, could thus be a good candidate for future missions, as a fourth mirror would allow better correction of optical aberrations. In this work, TMA and FMA have been optimized over different fields-of view. Performance limitations are then derived, which show that FMA seems promising for future missions. Radiometry aspects are discussed and preliminary tolerance analysis is carried out.Complex dynamics of a nonlinear aerospace structure: numerical continuation and normal modes
http://hdl.handle.net/2268/173404
Title: Complex dynamics of a nonlinear aerospace structure: numerical continuation and normal modes
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<br/>Author, co-author: Renson, Ludovic; Noël, Jean-Philippe; Kerschen, Gaëtan
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<br/>Abstract: This paper investigates the dynamics of a real-life aerospace structure possessing a strongly nonlinear component with multiple mechanical stops. A full-scale finite element model is built for gaining additional insight into the nonlinear dynamics that was observed experimentally, but also for uncovering additional nonlinear phenomena, such as quasiperiodic regimes of motion. Forced/unforced, damped/undamped numerical simulations are carried out using advanced techniques and theoretical concepts such as numerical continuation and nonlinear normal modes.A rigorous phase separation method for testing nonlinear structures
http://hdl.handle.net/2268/173388
Title: A rigorous phase separation method for testing nonlinear structures
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<br/>Author, co-author: Noël, Jean-Philippe; Renson, Ludovic; Grappasonni, Chiara; Kerschen, Gaëtan
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<br/>Abstract: The objective of the present paper is to develop a rigorous identification methodology of nonlinear normal modes (NNMs) of engineering structures. This is achieved by processing experimental measurements collected under broadband forcing. The use of such a type of forcing signal allows to excite multiple NNMs simultaneously and, in turn, to save testing time. A two-step methodology integrating nonlinear system identification and numerical continuation of periodic solutions is proposed for the extraction of the individual NNMs from broadband input and output data. It is demonstrated using a numerical cantilever beam possessing a cubic nonlinearity at its free end. The proposed methodology can be viewed as a nonlinear generalization of the phase separation techniques routinely utilized for experimental modal analysis of linear structures.Experimental and numerical study of the flight of geese
http://hdl.handle.net/2268/173335
Title: Experimental and numerical study of the flight of geese
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<br/>Author, co-author: Dimitriadis, Grigorios; Gardiner, James; Tickle, Peter; Codd, Jonathan; Nudds, Robert
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<br/>Abstract: The flight of barnacle geese at airspeeds representing high-speed migrating flight is investigated using experiments and simulations. The experimental part of the work involved the filming of three barnacle geese (Branta Leucopsis) flying at different airspeeds in a wind tunnel. The video footage was analysed in order to extract the wing kinematics. Additional information, such as wing geometry and camber was obtained from a 3D scan of a dried wing. An unsteady vortex lattice method was used to simulate the aerodynamics of the measured flapping motion. The simulations were used in order to successfully reproduce the measured body motion and thus obtain estimates of the aerodynamic forces acting on the wings. It was found that the mean of the wing pitch angle variation with time has the most significant effect on lift while the difference in the durations of the upstroke and downstroke has the major effect on thrust. The power consumed by the aerodynamic forces was also estimated; it was found that increases in aerodynamic power correspond very closely to climbing motion and vice versa. Root-mean-square values of the power range from 100 W to 240 W. Finally, it was observed that tandem flying can be very expensive for the trailing bird.Probabilistic Assessment of Lifetime of Low-Earth-Orbit Spacecraft: Uncertainty Propagation and Sensitivity Analysis
http://hdl.handle.net/2268/173327
Title: Probabilistic Assessment of Lifetime of Low-Earth-Orbit Spacecraft: Uncertainty Propagation and Sensitivity Analysis
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<br/>Author, co-author: Dell'Elce, Lamberto; Kerschen, Gaëtan
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<br/>Abstract: This paper is devoted to the probabilistic uncertainty quantification of orbital lifetime estimation of low-altitude satellites. Specifically, given a detailed characterization of the dominant sources of uncertainty, we map this input into a probabilistic characterization of the orbital lifetime through orbital propagation. Standard Monte Carlo propagation is first considered. The concept of drag correction is then introduced to facilitate the use of polynomial chaos expansions and to make uncertainty propagation computationally effective. Finally, the obtained probabilistic model is exploited to carry out stochastic sensitivity analyses, which in turn allow gaining insight into the impact uncertainties have on orbital lifetime. The proposed developments are illustrated using one CubeSat of the QB50 constellation.Modular bimorph mirrors for adaptive optics
http://hdl.handle.net/2268/172974
Title: Modular bimorph mirrors for adaptive optics
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<br/>Author, co-author: Rodrigues, Goncalo; Bastaits, Renaud; Roose, Stéphane; Stockman, Yvan; Gebhart, Sylvia; Schoenecker, Andreas; Villon, Pierre
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<br/>Abstract: This paper examines the possibility of constructing deformable mirrors for adaptive optics with a large number of degrees of freedom from silicon wafers with bimorph piezoelectric actuation. The mirror may be used on its own, or as a segment of a larger mirror. The typical size of one segment is 100to200mm ; the production process relies on silicon wafers and thick film piezoelectric material deposition technology; it is able to lead to an actuation pitch of the order of 5mm , and the manufacturing costs appear to grow only slowly with the number of degrees of freedom in the adaptive optics.Large deployable telescopes—also for lm-wavelengths?
http://hdl.handle.net/2268/172971
Title: Large deployable telescopes—also for lm-wavelengths?
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<br/>Author, co-author: Baier, Horst; Datashvili, Leri; Endler, Stephan; Roose, Stéphane; Stockman, Yvan
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<br/>Abstract: New demands for space and earth observations
drive the need for large apertures of 10 m and higher in
telescopes. This requires new types of alternative lightweight
and deployable primary reflector or lens concepts
with aerial densities of\3 kg/m2. Some syntheses between
optical and especially mechanical and material aspects for
large planar photon sieves and non-imaging telescopes are
discussed. Focus is put on large planar and highly perforated
membranes for photon sieves and shell-membrane
type deployable (parabolic) reflectors, respectively. The
reflecting surface of the latter is composed of specific
C-fiber reinforces silicone (CFRS) material. In addition to
possible shape control, emphasis is also given to reflective
coating of CFRS. Engineering challenges requiring future
activities are identified.Empirical modelling of the bifurcation behaviour of a bridge deck undergoing across-wind galloping
http://hdl.handle.net/2268/172925
Title: Empirical modelling of the bifurcation behaviour of a bridge deck undergoing across-wind galloping
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<br/>Author, co-author: Andrianne, Thomas; Dimitriadis, Grigorios
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<br/>Abstract: This work presents an empirical model capable to describe the galloping bifurcation behaviour of a bridge deck. It is based on a general polynomial form proposed by Novak, which we limit to the 5th order. The advantage of choosing this function for modelling the vertical force coefficient is that asymmetry of the even terms is enforced in order to reproduce the sub-critical aeroelastic behaviour of the bridge deck. The coefficients of the polynomial are identified from several pairs of displacement amplitudes and the corresponding airspeeds, measured in a wind tunnel during dynamic tests on the sectional bridge model. The identification is carried out using a first order harmonic balance technique. A stability analysis is presented in order to highlight the need of such a model to catch the complete bifurcation behaviour of the system. The resulting force coefficient of this full order model is compared to the well known models of Parkinson and Novak. Finally, the concept universal curve is used in order to discuss the galloping responses of square and rectangular cylinders, in comparison with the one of the bridge deck.Importance of structural damping in the dynamic analysis of compliant deployable structures
http://hdl.handle.net/2268/172759
Title: Importance of structural damping in the dynamic analysis of compliant deployable structures
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<br/>Author, co-author: Dewalque, Florence; Rochus, Pierre; Bruls, Olivier
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<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 low-cost missions with small satellites or cubesats. The mechanical behaviour of a tape spring is intrinsically complex and nonlinear involving buckling, hysteresis and self-locking phenomena. High-ﬁdelity 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 0-g 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.Space radiation parameters for EUI and the Sun Sensor of Solar Orbiter, ESIO and JUDE instruments
http://hdl.handle.net/2268/172491
Title: Space radiation parameters for EUI and the Sun Sensor of Solar Orbiter, ESIO and JUDE instruments
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<br/>Author, co-author: Rossi, Laurence; Jacques, Lionel; Halain, Jean-Philippe; Grodent, Denis; Renotte, Etienne; Thibert, Tanguy
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<br/>Abstract: This paper presents predictions of space radiation parameters for four space instruments performed by the Centre Spatial de Liège (ULg – Belgium); EUI, the Extreme Ultra-violet Instrument, on-board the Solar Orbiter platform; ESIO, Extreme-UV solar Imager for Operations, and JUDE, the Jupiter system Ultraviolet Dynamics Experiment, which was proposed for the JUICE platform.
For Solar Orbiter platform, the radiation environment is defined by ESA environmental specification and the determination of the parameters is done through ray-trace analyses inside the EUI instrument.
For ESIO instrument, the radiation environment of the geostationary orbit is defined through simulations of the trapped particles flux, the energetic solar protons flux and the galactic cosmic rays flux, taking the ECSS standard for space environment as a guideline. Then ray-trace analyses inside the instrument are performed to predict the particles fluxes at the level of the most radiation-sensitive elements of the instrument.
For JUICE, the spacecraft trajectory is built from ephemeris files provided by ESA and the radiation environment is modeled through simulations by JOSE (Jovian Specification Environment model) then ray-trace analyses inside the instrument are performed to predict the particles fluxes at the level of the most radiation-sensitive elements of the instrument.Solar simulation test up to 13 solar constants for the thermal balance of the Solar Orbiter EUI instrument
http://hdl.handle.net/2268/172490
Title: Solar simulation test up to 13 solar constants for the thermal balance of the Solar Orbiter EUI instrument
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<br/>Author, co-author: Rossi, Laurence; zhukova, Maria; Jacques, Lionel; Halain, Jean-Philippe; Hellin, Marie-Laure; Jamotton, Pierre; Renotte, Etienne; Rochus, Pierre; Liébecq, Sylvie; Mazzoli, Alexandra
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<br/>Abstract: Solar Orbiter EUI instrument was submitted to a high solar flux to correlate the thermal model of the instrument.
EUI, the Extreme Ultraviolet Imager, is developed by a European consortium led by the Centre Spatial de Liège for the Solar Orbiter ESA M-class mission. The solar flux that it shall have to withstand will be as high as 13 solar constants when the spacecraft reaches its 0.28AU perihelion.
It is essential to verify the thermal design of the instrument, especially the heat evacuation property and to assess the thermo-mechanical behavior of the instrument when submitted to high thermal load.
Therefore, a thermal balance test under 13 solar constants was performed on the first model of EUI, the Structural and Thermal Model. The optical analyses and experiments performed to characterize accurately the thermal and divergence parameters of the flux are presented; the set-up of the test, and the correlation with the thermal model performed to deduce the unknown thermal parameters of the instrument and assess its temperature profile under real flight conditions are also presented.An efficient flamelet-based combustion model for compressible flows
http://hdl.handle.net/2268/172448
Title: An efficient flamelet-based combustion model for compressible flows
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<br/>Author, co-author: Saghafian, Amirreza; Terrapon, Vincent; Pitsch, Heinz
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<br/>Abstract: A combustion model based on a flamelet/progress variable approach for high-speed flows is introduced. In the proposed formulation, the temperature is computed from the transported total energy and tabulated species mass fractions. Only three additional scalar equations need to be solved for the combustion model. Additionally, a flamelet library is used that is computed in a pre-processing step. This approach is very efficient and allows for the use of complex chemical mechanisms. An approximation is also introduced to eliminate costly iterative steps during the temperature calculation. To better account for compressibility effects, the chemical source term of the progress variable is rescaled with the density and temperature. The compressibility corrections are analyzed in an a priori study. The model is also tested in both Reynolds-averaged Navier–Stokes (RANS) and large-eddy simulation (LES) computations of a hydrogen jet in a supersonic transverse flow. Comparison with experimental measurements shows good agreement, particularly for the LES case. It is found that the disagreement between RANS results and experimental data is mostly due to the mixing model deficiencies and the presumed probability density functions used in the RANS formulation. A sensitivity study of the proposed model shows the importance of the compressibility corrections especially for the source term of the progress variable.Grey-box identification of a non-linear solar array structure using cubic splines
http://hdl.handle.net/2268/172274
Title: Grey-box identification of a non-linear solar array structure using cubic splines
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<br/>Author, co-author: Noël, Jean-Philippe; Kerschen, Gaëtan; Foltête, Emmanuel; Cogan, Scott
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<br/>Abstract: Most identification methods in non-linear structural dynamics assume in advance a mathematical model of the non-linearities. This is however possible in specific situations only, since non-linear effects may be caused by numerous phenomena and a priori knowledge is generally limited. The present paper investigates the usefulness of piecewise third-order polynomials, termed cubic splines, to identify the complex non-linear dynamics of solar arrays in their stowed configuration. The estimation of the model parameters is achieved using the frequency-domain non-linear subspace identification (FNSI) method. A distinct advantage of the FNSI approach is its capability to calculate accurately a large number of parameters, while maintaining an acceptable computational burden. This makes tractable the use of cubic splines to represent non-linearity in real-life mechanical systems, as the dimensionality of the inverse problem is known to increase dramatically in this case. The experimental structure of interest consists of two parallel aluminium plates assembled with bolted connections. This application is challenging because of the existence of impacts between the two plates at high excitation amplitude, and of the activation of complicated stiffness and damping mechanisms within the bolted connections.