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Implementation of the blade element theory to investigate the aerodynamic performance of a ducted fan UAV Guissart, Amandine ; ; Terrapon, Vincent et al Scientific conference (2015) Detailed reference viewed: 54 (22 ULg)Empirical modelling of the bifurcation behaviour of a bridge deck undergoing across-wind galloping Andrianne, Thomas ; Dimitriadis, Grigorios in Journal of Wind Engineering & Industrial Aerodynamics (2014), 135 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 ... [more ▼] 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. [less ▲] Detailed reference viewed: 60 (31 ULg)Statistical analysis of velocity measurements in anatmospheric boundary layer in wind tunnel Andrianne, Thomas ; Denoël, Vincent Poster (2014, September) Detailed reference viewed: 19 (3 ULg)Wind Tunnel Testing of a VTOL MAV Propeller in Tilted Operating Mode ; Dimitriadis, Grigorios ; Andrianne, Thomas et al in Proceedings of the 2014 International Conference on Unmanned Aircraft Systems (ICUAS 2014) (2014, May 30) This paper presents experimental results of the full 3-axis force vector and 3-axis moment vector acting on a propeller, commonly used for a Vertical Take Off and Landing Micro Aerial Vehicle (VTOL MAV ... [more ▼] This paper presents experimental results of the full 3-axis force vector and 3-axis moment vector acting on a propeller, commonly used for a Vertical Take Off and Landing Micro Aerial Vehicle (VTOL MAV). Measurements were carried out in a wind tunnel using a high resolution 6-axis force/moment sensor embedded in a customized test rig at several wind speeds, propeller rotational speeds and angles of the propeller shaft with respect to the air stream. Results show strong moments acting on the propeller in forward flight and unstable conditions in descending flight. Power calculations reveal a decrease in power consumption during slow forward flight and how motor efficiency can be maximized. [less ▲] Detailed reference viewed: 45 (10 ULg)Using POD and DMD for comparing CFD and experimental results in unsteady aerodynamics Guissart, Amandine ; Andrianne, Thomas ; Dimitriadis, Grigorios et al Conference (2014) Detailed reference viewed: 58 (12 ULg)Simulations, Normes, Soufflerie en ingénierie du vent : Quel outil pour quelle application ? ; Andrianne, Thomas ; Conference given outside the academic context (2013) Cette présentation a pour objectif de présenter les 3 moyens principaux de mener une étude technique dans le domaine de l'ingénierie du vent : simulation numérique, essais en soufflerie et normes. Les ... [more ▼] Cette présentation a pour objectif de présenter les 3 moyens principaux de mener une étude technique dans le domaine de l'ingénierie du vent : simulation numérique, essais en soufflerie et normes. Les avantages et inconvénients, ainsi que la complémentarité des 3 approches sont présentés et discutés. [less ▲] Detailed reference viewed: 79 (16 ULg)Experimental and numerical investigations of the torsional flutter oscillations of a 4:1 rectangular cylinder Andrianne, Thomas ; Dimitriadis, Grigorios in Journal of Fluids & Structures (2013), 41 The torsional flutter oscillations of a 4:1 rectangular cylinder around its pitching axis are investigated through wind tunnel experiments and numerical simulations. The rectangle’s responses to different ... [more ▼] The torsional flutter oscillations of a 4:1 rectangular cylinder around its pitching axis are investigated through wind tunnel experiments and numerical simulations. The rectangle’s responses to different initial conditions and turbulence excitations at various wind tunnel airspeeds are recorded. Timeresolved Particle Image Velocimetry measurements are taken at two different airspeeds, when the rectangle undergoes Limit Cycle Oscillations. Aeroelastic simulations are carried out using the Discrete Vortex Method and the resulting responses are compared to the experimental measurements. The Common-base Proper Orthogonal Decomposition method is used to analyse and compare the measured and simulated unsteady flow fields around the rectangle. A discussion of the participation of each mode in the different states of the flow-field is presented, at two different amplitudes of oscillation. The Motion Induced Vortex (MIV) is identified as the fundamental cause of the torsional flutter phenomenon and its role over a complete cycle is studied. MIV-induced oscillations can be started either by a suitable initial disturbance or by a second, nearly linear self-excited instability that causes negative aerodynamic damping. The combination of these two instabilities results in a complete description of the torsional flutter of the rectangle. [less ▲] Detailed reference viewed: 147 (41 ULg)Torsional flutter of bluff bodies Terrapon, Vincent ; Guissart, Amandine ; Andrianne, Thomas et al Scientific conference (2013, July 15) Detailed reference viewed: 47 (17 ULg)Using Proper Orthogonal Decomposition and Dynamic Mode Decomposition Methods for Comparing CFD Results Experimental Measurements Guissart, Amandine ; Andrianne, Thomas ; Dimitriadis, Grigorios et al in Proceedings of the 15th International Forum on Aeroelasticity and Structural Dynamics, IFASD 2013 (2013, June 26) A method for the quantitative comparison of numerical and/or experimental data of unsteady aerodynamics around static and oscillating bodies is introduced. It is based on Proper Orthogonal Decomposition ... [more ▼] A method for the quantitative comparison of numerical and/or experimental data of unsteady aerodynamics around static and oscillating bodies is introduced. It is based on Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) to extract the dominant structures of the unsteady flow. The proposed method is applied to spatio-temporal data for the flow around a 4:1 rectangular cylinder. Exper- imental data are obtained from wind tunnel testing and two dimensional Time-resolved Particle Image Velocimetry (Tr-PIV) measurements, while unsteady Reynolds Averaged Navier-Stokes (uRANS) are used to compute numerical results. It is demonstrated that the two approaches are complementary and represent a powerful tool that enables the analysis and the quantitative comparison of the main spatial (POD) and temporal (DMD) characteristics of unsteady aerodynamic data. [less ▲] Detailed reference viewed: 184 (52 ULg)Integrating Experimental and Computational Fluid Dynamics approaches using Proper Orthogonal Decomposition Techniques Andrianne, Thomas ; ; Guissart, Amandine et al in Progress in Aerospace Sciences (2013) 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 ... [more ▼] 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. [less ▲] Detailed reference viewed: 320 (40 ULg)Using Proper Orthogonal Decomposition Methods for Comparing CFD Results to Experimental Measurements Andrianne, Thomas ; Guissart, Amandine ; Terrapon, Vincent et al Scientific conference (2012, December 07) This work presents a method for quantitative comparison of numerical results to experimental measurements. It is based on the concept of Proper Orthogonal Decomposition. This technique is selected in ... [more ▼] This work presents a method for quantitative comparison of numerical results to experimental measurements. It is based on the concept of Proper Orthogonal Decomposition. This technique is selected in order to compare the unsteady aerodynamic flows around static and oscillating bodies obtained from wind tunnel testing and numerical simulations. Two dimensional Time-resolved Particle Image Velocimetry measurements are carried out on the upper surface a 4:1 rectangular cylinder. Simulations are performed using unsteady Reynolds-Averaged Navier-Stokes and an unsteady Discrete Vortex Method. It is demonstrated that the proposed technique is a good preliminary step for comparing the main characteristics of unsteady aerodynamic data. [less ▲] Detailed reference viewed: 67 (25 ULg)Using Proper Orthogonal Decomposition Methods for Comparing CFD Results to Experimental Measurements Andrianne, Thomas ; Guissart, Amandine ; Terrapon, Vincent et al in Proceedings of the 5th Symposium on Integrating CFD and Experiments in Aerodynamics (Integration 2012) (2012, October 03) This work presents a method for quantitative comparison of numerical results to experimental measurements. It is based on the concept of Proper Orthogonal Decomposition. This technique is selected in ... [more ▼] This work presents a method for quantitative comparison of numerical results to experimental measurements. It is based on the concept of Proper Orthogonal Decomposition. This technique is selected in order to compare the unsteady aerodynamic flows around static and oscillating bodies obtained from wind tunnel testing and numerical simulations. Two dimensional Time-resolved Particle Image Velocimetry measurements are carried out on the upper surface a 4:1 rectangular cylinder. Simulations are performed using unsteady Reynolds-Averaged Navier-Stokes and an unsteady Discrete Vortex Method. It is demonstrated that the proposed technique is a good preliminary step for comparing the main characteristics of unsteady aerodynamic data. [less ▲] Detailed reference viewed: 254 (47 ULg)Damping identification of linear dynamic systems using Common-base Proper Orthogonal Decomposition Andrianne, Thomas ; Dimitriadis, Grigorios in Proceedings of ISMA2012 (2012, September 19) This paper presents a novel identification technique of the modal damping of linear systems. It is based on the Proper Orthogonal Decomposition (POD) of the free response of the system and extended to the ... [more ▼] This paper presents a novel identification technique of the modal damping of linear systems. It is based on the Proper Orthogonal Decomposition (POD) of the free response of the system and extended to the Common-base POD (CPOD) approach. Different initial conditions are applied to the system and the corresponding free responses are considered simultaneously. The CPOD technique leads to a unique vector basis which is likely to contain more information about the dynamics of the system than a vector basis obtained by the classic POD technique, based on one set of initial conditions only. The ability of the technique to estimate the modal damping is demonstrated on a simulated mass-spring-damper system and an experimental system. Good agreement is shown between the damping estimates of the CPOD technique and the ones of the LSCF technique. The advantage and limitations of the present technique are discussed. [less ▲] Detailed reference viewed: 55 (3 ULg)Comparison of numerical results to experimental measurements using Proper Orthogonal Decomposition Andrianne, Thomas ; Dimitriadis, Grigorios Scientific conference (2012, May 24) Detailed reference viewed: 30 (6 ULg)Numerical simulations of torsional flutter oscillations of a bluff body: Energy issues, GraSMech poster session Andrianne, Thomas ; Dimitriadis, Grigorios Poster (2012, May) The possibility of harvesting energy from aeroelastic phenomena is assessed through numerical simulations. The unsteady aerodynamics around an aeroelastic structure are modeled using the Discrete Vortex ... [more ▼] The possibility of harvesting energy from aeroelastic phenomena is assessed through numerical simulations. The unsteady aerodynamics around an aeroelastic structure are modeled using the Discrete Vortex Method (DVM). The Torsional Flutter oscillations of a rectangular cylinder are studied in this work. The phenomenon is characterized by Limit Cycle Oscillations (LCOs) around the pitch axis of the rectangle. The complete bifurcation behaviour is investigated numerically and compared to wind tunnel measurements for validation. The energy issues are investigated in terms of the sensibility of the energy output to variations in the structural damping. [less ▲] Detailed reference viewed: 77 (16 ULg)A Cross-Validation Approach to Approximate Basis Function Selection of the Stall Flutter Response of a Rectangular Wing in a Wind Tunnel ; ; Andrianne, Thomas et al in Proceedings of the 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference (2012, April 25) The stall flutter response of a rectangular wing in a low speed wind tunnel is modelled using a nonlinear difference equation description. Static and dynamic tests are used to select a suitable model ... [more ▼] The stall flutter response of a rectangular wing in a low speed wind tunnel is modelled using a nonlinear difference equation description. Static and dynamic tests are used to select a suitable model structure and basis function. Bifurcation criteria such as the Hopf condition and vibration amplitude variation with airspeed were used to ensure the model was representative of experimentally measured stall flutter phenomena. Dynamic test data were used to estimate model parameters and estimate an approximate basis function. [less ▲] Detailed reference viewed: 77 (12 ULg)Discrete Vortex Simulations of the torsional flutter oscillations of a 4:1 rectangular cylinder Andrianne, Thomas ; Dimitriadis, Grigorios in Proceedings of the 53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference (2012, April 24) This work presents aeroelastic simulations of a 2D bluff-body around its pitching degree of freedom. The numerical tool consists in an aerodynamic solver based on the Discrete Vortex Method (DVM), coupled ... [more ▼] This work presents aeroelastic simulations of a 2D bluff-body around its pitching degree of freedom. The numerical tool consists in an aerodynamic solver based on the Discrete Vortex Method (DVM), coupled with a linear structural model. The shape of the bluff-body is a sharp edged rectangular cylinder with a side ratio equal to 4. The numerical results are compared to the experimental measurements recently obtained by the authors.8 The validation is carried out in three steps: first the frequency content of the flow-field in the wake of the static body is investigated. Then the simulated unsteady flow-field around the imposed pitching motion of the body is compared to experimental flow visualizations. This comparison is performed using Proper Orthogonal Decomposition (POD). Finally, the simulation of the global aeroelastic behaviour, based on the coupling of the DVM code to the structural model of the pitching degree of freedom is carried out and the results are compared to measured aeroelastic responses.. Very good agreements are found between numerical and experimental results, demonstrating the capabilities of the numerical tool to simulate complex unsteady aerodynamics around an oscillating bluff-body. [less ▲] Detailed reference viewed: 43 (13 ULg)Damping identification of lightly damped linear dynamic systems using Common-base Proper Orthogonal Decomposition Andrianne, Thomas ; Dimitriadis, Grigorios in Mechanical Systems & Signal Processing (2012), 28 This paper presents a new technique to identify the damping of linear systems. It is developed from the Proper Orthogonal Decomposition (POD) of the free response of the system and extended to the ... [more ▼] This paper presents a new technique to identify the damping of linear systems. It is developed from the Proper Orthogonal Decomposition (POD) of the free response of the system and extended to the recently proposed Common-base POD (CPOD). The present application of CPOD considers simultaneously several free responses of the system to different initial conditions. The eigen-decomposition of the co-variance matrix leads to a unique vector basis which is likely to contain more information about the dynamics of the system than a vector basis obtained by the classic POD technique. The ability of the technique to estimate the mode shapes and the modal damping is demonstrated on a simulated mass-spring-damper system. Two different distributions of masses are considered in order to confront the CPOD analysis to the intrinsic limitation of POD, i.e. that the mode shapes are identified exactly only if the mass matrix is proportional to the identity matrix. It is shown that the identification of the damping is still possible when the modes are not orthonormal. The robustness of the technique is demonstrated in the presence of noise in the responses of the system and through an experimental application with comparison with other identifications techniques. [less ▲] Detailed reference viewed: 84 (15 ULg)Experimental and Numerical Investigations of the Aeroelastic Stability of Bluff Structures Andrianne, Thomas Doctoral thesis (2012) The study of the dynamic interactions between the wind and civil engineering structures has become increasingly important over the last few decades. Most of these structures are aerodynamically "bluff ... [more ▼] The study of the dynamic interactions between the wind and civil engineering structures has become increasingly important over the last few decades. Most of these structures are aerodynamically "bluff" and are becoming more flexible. Bluff-body aeroelasticity is a very challenging research area due to the unsteadiness and nonlinearity of the aerodynamic loading. This thesis presents the investigation of three aeroelastic phenomena affecting bluff-bodies: Vortex Induced Vibration (VIV), Galloping and Torsional Flutter. For each instability, extensive experimental studies are carried out in the wind tunnel. Innovative analysis, based on the Common-base Proper Orthogonal Decomposition (CPOD) method is used to study the flow visualization data. The VIV phenomenon is studied on a flexible tube with a circular cross-section, supported from its midpoint. A CPOD-based input-output model is developed to describe the system. The galloping instability is studied on a generic bridge section. A complete analysis of the aeroelastic behaviour of the structure is presented and a new polynomial empirical model is developed, which reflects accurately the nonlinear nature of the system. The torsional flutter phenomenon is extensively studied for two different structures: a generic bridge deck and a rectangular cylinder. The Motion Induced Vortex is identified as the fundamental cause of this aeroelastic phenomenon, on the basis of the analysis of the flow around the oscillating rectangle. In addition, it is demonstrated that the quasi-steady theory is not adapted to estimate the onset velocity of torsional flutter. Finally, a 2D aeroelastic simulation code, based on the Discrete Vortex Method (DVM) is developed. The non-linear aerodynamics around the body are well reproduced, allowing the simulation of all the aeroelastic instabilities investigated experimentally. [less ▲] Detailed reference viewed: 301 (81 ULg)Experimental Analysis of the Bifurcation Behaviour of a Bridge Deck Undergoing Across-Wind Galloping Andrianne, Thomas ; Dimitriadis, Grigorios in De Roeck, G.; Degrande, G.; Lombaert, G. (Eds.) et al Proceedings of the 8th International Conference on Structural Dynamics, EURODYN 2011 (2011, July 05) The phenomenon of aeroelastic galloping is a very important design consideration for bridges and other slender structures. It has been investigated by a number of researchers but, most frequently, the ... [more ▼] The phenomenon of aeroelastic galloping is a very important design consideration for bridges and other slender structures. It has been investigated by a number of researchers but, most frequently, the analysis is limited to quasi-steady aerodynamic and linearized aeroelastic considerations. Such treatment has been shown to be effective for simple cross-sectional shapes, such as rectangles. In this work, an aeroelastic model of a realistic bridge deck cross-section is tested in a low speed wind tunnel. Both static and dynamic tests are carried out and the resulting force and vibration measurements are presented. The static force results are used to set up a quasi-steady mathematical model. The dynamic responses are used to draw a complete bifurcation diagram within a chosen airspeed range and to discuss the stability of the system. It is shown that the experimental system undergoes a subcritical Hopf bifurcation, its phase space including both a stable and an unstable limit cycle. As consequence, throughout the chosen airspeed, the system can either remain stable or undergo limit cycle oscillations. The quasi-steady analysis fails completely in capturing this type of behaviour. The predicted galloping onset speed is too conservative and the predicted oscillation amplitudes too high. The reason for this failure is the fact that the quasi-steady mathematical model is incapable of modelling subcritical Hopf bifurcations. [less ▲] Detailed reference viewed: 102 (21 ULg) |
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