http://hdl.handle.net/2268/81 Search this channel search http://orbi.ulg.ac.be/simple-search http://hdl.handle.net/2268/148542 Title: Frequency-domain subspace identification of nonlinear mechanical systems <br/> <br/>Author, co-author: Noël, Jean-Philippe; Kerschen, Gaëtan <br/> <br/>Abstract: The objective of the present paper is to address the identification of a real-life strongly nonlinear space structure, the EADS-Astrium SmallSat spacecraft. To this end, a new nonlinear subspace identification method formulated in the frequency domain is exploited, referred to as the FNSI method. The frequency response functions of the underlying linear spacecraft and the amplitudes of the nonlinear internal forces are estimated based on a periodic-random data set corrupted by noise. This application is challenging for several reasons, including high modal density, highly non-proportional damping and the non-smooth nature of the nonlinearities. http://hdl.handle.net/2268/147732 Title: Integrating Experimental and Computational Fluid Dynamics approaches using Proper Orthogonal Decomposition Techniques <br/> <br/>Author, co-author: Andrianne, Thomas; Yasue, Kanako; Guissart, Amandine; Terrapon, Vincent; Dimitriadis, Grigorios; Kuchi-Ishi, Shigeru; Watanabe, Shigeya <br/> <br/>Abstract: The concept of Proper Orthogonal Decomposition (POD) is used to integrate Experimental Fluid Dynamics (EFD) and Computational Fluid Dynamics (CFD) approaches. The key idea is to take advantage of the optimality of the POD technique and its capability to extract the most energetic patterns of complex aerodynamic flow fields. First, the concept of Modal Assurance Criterion (MAC) is used to obtain a simple quantitative criterion to compare EFD measurements to CFD results. The comparison is based on the POD modes, extracted from each set of data. The analysis of the energy content of the modes allows to draw important conclusions about the role of the latter. The method is applied in the study of the flow field around a rectangular cylinder, which is either static or oscillating in a low-speed flow field. The second EFD/CFD integration technique deals with the reconstruction of a flow field from measured data, making use of CFD simulation results. The POD modes are first extracted from several CFD data sets, using a snapshot POD approach. Then the entire flow field of measured data can be reconstructed using a gappy POD method. The technique is applied to the transonic flow around a civil aircraft type wind tunnel model. The EFD measurements consist in pressure coefficient data from pressure ports or pressure-sensitive paint. It is shown that the complete flow field can be reconstructed from the pressure data with satisfactory accuracy and at relatively low computational cost. The work demonstrates the potential of the POD technique to integrate EFD and CFD data, leading to a combined, validated and complete analysis of the flow under consideration. http://hdl.handle.net/2268/147237 Title: To heal or not to heal: modeling the influence of oxygen during fracture healing. <br/> <br/>Author, co-author: Carlier, Aurélie; Geris, Liesbet; Van Oosterwyck, Hans http://hdl.handle.net/2268/147236 Title: Modeling the influence of oxygen in delayed bone fracture healing. <br/> <br/>Author, co-author: Carlier, Aurélie; Geris, Liesbet; Van Oosterwyck, Hans http://hdl.handle.net/2268/147226 Title: Multiscale modeling of in the influence of oxygen during bone fracture healing. <br/> <br/>Author, co-author: Carlier, Aurélie; Van Gastel, Nick; Carmeliet, Geert; Geris, Liesbet; Van Oosterwyck, Hans http://hdl.handle.net/2268/147225 Title: Multiscale modelling of the influence of VEGF on sprouting angiogenesis. <br/> <br/>Author, co-author: Carlier, Aurélie; Geris, Liesbet; Van Oosterwyck, Hans http://hdl.handle.net/2268/147223 Title: A multiscale model of sprouting angiogenesis during fracture healing. <br/> <br/>Author, co-author: Carlier, Aurélie; Geris, Liesbet; Van Oosterwyck, Hans http://hdl.handle.net/2268/147222 Title: Multiscale modeling of sprouting angiogenesis: tip cells are selected for the top. <br/> <br/>Author, co-author: Carlier, Aurélie; Geris, Liesbet; Van Oosterwyck, Hans http://hdl.handle.net/2268/147221 Title: Tip cells at the top: a multiscale model of sprouting angiogenesis. <br/> <br/>Author, co-author: Carlier, Aurélie; Geris, Liesbet; Van Oosterwyck, Hans http://hdl.handle.net/2268/147220 Title: To heal or not to heal: a multiscale model of the influence of oxygen during bone fracture healing. <br/> <br/>Author, co-author: Carlier, Aurélie; Geris, Liesbet; Van Oosterwyck, Hans http://hdl.handle.net/2268/147218 Title: A multiscale model of the influence of oxygen during bone fracture healing. <br/> <br/>Author, co-author: Carlier, Aurélie; Geris, Liesbet; Van Oosterwyck, Hans http://hdl.handle.net/2268/147066 Title: Étude et développement de techniques de métrologie de déplacements en lumière cohérente en infrarouge thermique <br/> <br/>Author, co-author: Vandenrijt, Jean-François <br/> <br/>Abstract: This thesis presents the works realised to apply ESPI and digital holography techniques at 10 µm for the monitoring of surface displacements of aerospace structures and space re- flectors. We consider objects with dimensions from a few tens of centimetres to more than one metre and with measurement ranges extending from a few micrometers to hundreds of micrometers. For specular surfaces where no diffusive coatings are allowed, we present the speckle pro- jection technique. We implement it in the special case of space reflectors. The use of a dif- fuser as the light source makes optical design much more simple and flexible than tradi- tional interferometric techniques. It allows use to consider its application on a wide range of form. We have also taken profit of the LWIR range to realise for the first time simultaneous dis- placement and temperature measurements with the same infrared detector. For this, we propose different computation techniques of the thermal image out of the phase shifted ESPI specklegram acquisitions.; Cette thèse présente les travaux réalisés pour appliquer les techniques interférométriques, que sont l’ESPI et l’holographie digitale à 10 µm, pour la mesure de déplacements de surface de structures aéronautiques ou de réflecteurs spatiaux. Nous envisageons la mesure d’objets dont les dimensions varient de quelques dizaines de centimètres à plus d’un mètre, avec une gamme de mesures allant de quelques micromètres à plusieurs centaines de micro- mètres. Pour les surfaces spéculaires pour lesquelles l’application d’un revêtement diffusant n’est pas permise, nous présentons la technique de projection de speckle. Nous la mettons en œuvre pour le cas particulier des réflecteurs spatiaux. L’utilisation d’un diffuseur comme source lumineuse rend les montages optiques beaucoup plus simples et flexibles que les techniques interférométriques habituelles. Elle nous permet ainsi d’envisager la mesure d’un large éventail de forme. Nous avons également tiré profit de l’utilisation du domaine de longueur d’onde de l’infra- rouge thermique pour réaliser pour la première fois la mesure simultanée de déplacements et de températures à partir d’un même détecteur infrarouge. Pour cela, nous proposons dif- férentes techniques de calcul de l’image thermique à partir des specklegrammes acquis par décalage de phase en ESPI. http://hdl.handle.net/2268/147038 Title: FAO Training in Crop Yield Forecasting. Improvement of the Crop Yield Forecasting System (CYFS) in Armenia: a new approach for satellite data integration. ARMENIA - Yerevan - January 2013. <br/> <br/>Author, co-author: Denis, Antoine <br/> <br/>Abstract: This manual describes a methodology to prepare the remote sensing database needed for the crop yield forecasting methodology developped by the University of Liege, in the case of Armenia.This manual has been written for the training in Crop Yield Forecasting for Armenia that occurred between 21st and 25th January 2013 in Erevan – Armenia in the framework of the “EC/FAO Programme on information systems to improve food security decision-making in the European Neighbourhood Policy (ENP) East area”. This manual is intended to cover the Remote Sensing part only of the general CYFS. Despite written for the Armenian training this manual can serve as an example for all other countries. http://hdl.handle.net/2268/146906 Title: Validation of the Structural-Thermal-Model of the Small Earth Observation Satellite Flying Laptop <br/> <br/>Author, co-author: Steinmetz, Fabian; Lengowski, Michael; Winter, Daniel; Salvador, Lucas; Röser, Hans-Peter; Rochus, Pierre <br/> <br/>Abstract: Thorough thermal design and testing is compulsory for every satellite mission. A well-known thermal behavior of the entire satellite system is therefore indispensable and needs to be verified during the spacecraft development. A Structural-Thermal-Model (STM) was constructed for the Flying Laptop, a satellite currently being developed at the Institute of Space Systems (IRS) of the University of Stuttgart, which enables the validation of mechanical and thermal simulations for the satellite’s Flight-Model. The STM was vibration and thermal-vacuum tested at the Centre Spatial Liège (CSL). This paper will de-scribe the design and construction of the STM as well as the facilities and test equipment used for the tests. Conclusions will be drawn from the actual test results. http://hdl.handle.net/2268/146902 Title: Validation of the Structural-Thermal Model of the Small Earth Observation Satellite Flying Laptop <br/> <br/>Author, co-author: Steinmetz, Fabian; Lengowski, Michael; Winter, Daniel; Salvador, Lucas; Röser, Hans-Peter; Rochus, Pierre <br/> <br/>Abstract: Thorough thermal design and testing is compulsory for every satellite mission. A well-known thermal behavior of the entire satellite system is therefore indispensable and needs to be verified during the spacecraft development. A Structural-Thermal-Model (STM) was constructed for the Flying Laptop, a satellite currently being developed at the Institute of Space Systems (IRS) of the University of Stuttgart, which enables the validation of mechanical and thermal simulations for the satellite’s Flight-Model. The STM was vibration and thermal-vacuum tested at the Centre Spatial Liège (CSL). This paper will de-scribe the design and construction of the STM as well as the facilities and test equipment used for the tests. Conclusions will be drawn from the actual test results. http://hdl.handle.net/2268/146867 Title: Nonparametric subspace identification of nonlinear structures - Application to a spacecraft <br/> <br/>Author, co-author: Noël, Jean-Philippe; Kerschen, Gaëtan <br/> <br/>Abstract: The objective of the present paper is to address the identification of a strongly nonlinear satellite structure by exploiting a new nonlinear subspace identification method formulated in the frequency domain, referred to as the FNSI method. The modal parameters of the underlying linear structure and the coefficients of the nonlinear internal forces will be estimated by this approach. Moreover, because a priori knowledge about nonlinear behaviour may be limited, the paper also proposes a nonparametric spline-based modelling strategy, encapsulated in the FNSI method. The application of interest is the SmallSat spacecraft developed by EADS-Astrium, which possesses an impact-type nonlinear device consisting of eight mechanical stops limiting the motion of an inertia wheel mounted on an elastomeric interface. http://hdl.handle.net/2268/146859 Title: Dynamic Stall and Stall Flutter Simulations for a 2D Airfoil Using Viscous-Inviscid Coupling <br/> <br/>Author, co-author: Rothkegel Ide, José Ignacio; Dimitriadis, Grigorios <br/> <br/>Abstract: An interactive boundary layer model has been developed and coupled with a pitch plunge airfoil in 2d in order to solve the unsteady flow around the airfoil when undergoing light dynamic stall. The inviscid problem is solved by means of a panel method, by the discretization of the airfoil into vortex panels. The boundary layer is solved in a mixed manner, starting the solution in a direct way by imposing the external velocity and continuing it in an inverse way by imposing the displacement thickness. The solution of the boundary layer equations is carried out using a finite volume scheme. Viscous-inviscid coupling is preformed through the imposition of a permeation velocity on the skin panels of the airfoil and the addition of a free wake at each separation point. http://hdl.handle.net/2268/146707 Title: Damage detection and local resonances model in CFRP composite material by vibrothermography <br/> <br/>Author, co-author: Demy, Philippe; Golinval, Jean-Claude; Simon, Daniel <br/> <br/>Abstract: Vibrothermography (VT) is an active non destructive technique able to detect singularities like delamination, even if the defect internal faces are in contact. Under sonic or ultrasonic mechanical vibrations, a delamination may behave like a heat source principally due to friction between the rubbing faces and/or stress concentration in the area. The present article focuses on the understanding of the underlying phenomenon so-called "local resonances" and its correlation with the presence of temperature peaks observed at certain frequencies. For this purpose, a simplified finite element modal analysis of the delamination model is compared with the heating rate vs. frequency data's acquired by an infrared camera. Then, some conclusive results of sine sweep and chirp testing will be presented and discussed in regards to this theory. http://hdl.handle.net/2268/146508 Title: Development of a high-order interior penalty discontinuous Galerkin method for compressible turbulent flows. Application to Reynolds-averaged Navier-Stokes and large eddy simulations <br/> <br/>Author, co-author: Drosson, Marcus <br/> <br/>Abstract: Over the last decade several studies and workgroups came to the conclusion that high-order discretisation schemes are the most suited to overcome the limitations of today’s flow solvers. The latter are at most second-order accurate and therefore often deliver poor results on currently used meshes. Within this context, discontinuous Galerkin (DG) methods have recently been identified as having the biggest potential for future flow solvers. Further research is however needed to improve the computational efficiency and the robustness of these schemes. Both issues are faced in the subsequent chapters of the thesis. The first part of the thesis is devoted to the solution of the Reynolds-averaged Navier-Stokes (RANS) equations using an interior penalty (IP) formulation. Whereas the intention is not to develop new turbulence models, the focus lies on the adaptation of existing models to the particular features of high-order discretisation schemes. In contrast to classical low-order methods, high-order schemes are prone to Gibbs oscillations which – if no care is taken – can lead to the breakdown of the algorithm. Given the stability issues caused by negative values of the eddy viscosity, different changes of the one-equation Spalart-Allmaras (S-A) model are discussed. Whilst having identical sparsity patterns as the popular second Bassi-Rebay scheme (BR2), the simpler IP formulation is up to 30% less time-consuming. Unfortunately, its stability strongly depends on a seemingly more or less arbitrary penalty parameter. As this parameter also effects the conditioning of the resulting system of discretised equations, its choice is of utmost importance. This might explain why the IP formulation has received only little attention over the past decades. The thesis analyses for the first time the use of the interior penalty discretisation to solve a system of RANS equations. One of the principal contributions of this work is the generalisation of the penalty parameter to anisotropic meshes and a highly variable viscosity. Several numerical examples are presented to illustrate the effect of the newly proposed definition of the penalty parameter. The focus of the second part lies on turbulent boundary layer resolution. Based on detailed grid convergence analyses as a function of interpolation order, element type and grid size, clear guidelines for the choice of boundary layer meshes for practical applications are provided. Besides straight boundaries, the effect of boundary curvature or a hybrid discretisation are investigated. Moreover, the concept of “quasi-straight” elements is introduced. Following this innovative approach, the accuracy of the calculated shear friction can further be improved by a proper choice of the position of the inner-element nodes, without increasing the total number of unknowns. Finally, several numerical applications clearly demonstrate the potential of the method to solve industrial problems. In the last part, large eddy simulations of the Taylor-Green vortex and the decay of homogeneous isotropic turbulence are presented. This last chapter constitutes a first step towards the use of discontinuous Galerkin methods for large eddy simulations. Besides a validation study for the Smagorinsky and the WALE subgrid scale model, the resolution requirements of resolved LES are determined. Furthermore different subgrid filters are compared and the choice of the Smagorinsky constant in the case of filtered LES is briefly examined. http://hdl.handle.net/2268/145481 Title: FAO Training in Crop Yield Forecasting. Crop Yield Forecasting Methodology Enhancement – Remote sensing. Erevan 21 - 25 January 2013. <br/> <br/>Author, co-author: Denis, Antoine <br/> <br/>Abstract: Power point presentation of the FAO training "Crop Yield Forecasting Methodology Enhancement – Remote sensing", held in Erevan, Armenia, 21 - 25 January 2013 at ARMSTATEHYDROMET. The main objective of this training was the improvement of the Crop Yield Forecasting System (CYFS) in Armenia by introducing a new approach for satellite data integration (use of TIMESAT software and METOP AVHRR NDVI images). This training was held in the framework of the "EC/FAO Programme on Information Systems to Improve Food Security Decision-Making in the European Neighbourhood Policy (ENP) East Area GCP/GLO/275/EC".