Les conditions conduisant aux vibrations hydroélastiques de bord de fuite sont étudiées sur un hy... more Les conditions conduisant aux vibrations hydroélastiques de bord de fuite sont étudiées sur un hydrofoil NACA0015 en Aluminium monté en configuration encastrée-libre dans un tunnel hydrodynamique. Les essais ont été menés pour des nombres de Reynolds compris entre 2 × 10 5 et 9 × 10 5 et différents angles d'incidence de 0 à 10°. De la vibrométrie laser a été utilisée pour identifier la réponse vibratoire de l'hydrofoil. De la vélocimétrie par image de particules résolue en temps (TR-PIV) a aussi été utilisée pour caractériser l'écoulement et discuter de l'origine hydrodynamique du phénomène. Ce travail a pour objectif de décrire les différentes configurations conduisant à un couplage fort entre l'écoulement et un mode d'hydrofoil caractérisé par un ventre de vibration au bord de fuite. Des amplitudes de vibration significatives ont ainsi été observées pour des angles d'incidence compris entre 3.5°et 8.5°. L'analyse de l'écoulement de bord de fuite a également révélé que le comportement de la couche limite intrados au niveau du décollement de bord de fuite joue un rôle essentiel dans le mécanisme d'excitation.
HAL (Le Centre pour la Communication Scientifique Directe), Jul 5, 2022
Wind tunnel tests of 2D rough cylinders are presented. The goal is to simulate the alternate vort... more Wind tunnel tests of 2D rough cylinders are presented. The goal is to simulate the alternate vortex shedding in flow regimes encountered in wind engineering applications, where the full scale Reynolds number is larger than the one that can be reproduced in wind tunnel with small scaled models. Measurements are mainly the synchronized unsteady wall pressures on the cylinder which are post processed using bi-orthogonal decompositions. By comparing the small scale results with those from a previous large scale experiment, we show that the technique of rough cylinder is incomplete and can approach roughly global parameters only.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 13, 2022
The present work focuses on flutter mitigation of a flat plate section model using passive linear... more The present work focuses on flutter mitigation of a flat plate section model using passive linear and nonlinear vibration absorbers for a two branches (coupled-mode flutter and stall flutter) post-critical flutter scenario. Experiments have been done in a subsonic wind tunnel using an aeroelastic section model setup. Numerical results have been obtained using an analytical section model for which the pitch-plunge-absorbers equations of motion are combined with a nonlinear unsteady aerodynamic formulation. Without control, the two branches post-critical flutter scenario is well captured by the numerical model. Using linear or non linear vibrations absorbers in plunge, qualitative agreement are found. Adding a non linear absorber in pitch, numerical prediction does not match the one obtained in wind tunnel. This study however confirms that a combination of absorbers in both pitch and plunge is the best solution to delay the critical velocity and that a proper numerical tuning should also help to optimize the LCOs mitigations.
HAL (Le Centre pour la Communication Scientifique Directe), Nov 14, 2011
Temporal simulations are increasingly performed for wind effects analysis of flexible structures.... more Temporal simulations are increasingly performed for wind effects analysis of flexible structures. By comparison with classical techniques such as spectral methods, temporal simulations provide advantage of easily combining different kinds of load, can take nonlinearities into account and are also the only way to reproduce transient behaviours. In that context this study deals with the transient response of a two degrees-of-freedom streamlined bridge deck section submitted to a single gust. Experimental evidence of the potentially high level of transient energy amplification due to that kind of extraneously excitation have been recently demonstrated for an airfoil section [3, 4] and for a streamlined bridge deck section [5], below the critical flutter wind speed. The present study then focuses on the validation of a time-dependant model, based on a simple formulation of both the motion-dependant and buffeting forces, for catching that kind of transient behaviour. A parametric study is done in order to highlight the impact of the pitch-plunge frequency ratio on the energy amplification below the critical flutter wind speed.
HAL (Le Centre pour la Communication Scientifique Directe), Jul 2, 2012
ABSTRACT This paper explores the dynamical response of a two-degree-of-freedom flat plate undergo... more ABSTRACT This paper explores the dynamical response of a two-degree-of-freedom flat plate undergoing classical coupled-mode flutter in a wind tunnel. Tests are performed at low Reynolds number (Re~2.5×104), using an aeroelastic set-up that enables high amplitude pitch–plunge motion. Starting from rest and increasing the flow velocity, an unstable behaviour is first observed at the merging of frequencies: after a transient growth period the system enters a low amplitude limit-cycle oscillation regime with slowly varying amplitude. For higher velocity the system transitions to higher-amplitude and stable limit cycle oscillations (LCO) with amplitude increasing with the flow velocity. Decreasing the velocity from this upper LCO branch the system remains in stable self-sustained oscillations down to 85% of the critical velocity. Starting from rest, the system can also move toward a stable LCO regime if a significant perturbation is imposed. Those results show that both the flutter boundary and post-critical behaviour are affected by nonlinear mechanisms. They also suggest that nonlinear aerodynamic effects play a significant role.
HAL (Le Centre pour la Communication Scientifique Directe), Nov 22, 2015
In the context of energy harvesting we address the coupling between a flexible flag and its flagp... more In the context of energy harvesting we address the coupling between a flexible flag and its flagpole equipped so that it constitutes a spring-mass oscillator. An extensive set of experiments is carried out in wind tunnel for various flag and oscillator parameters. Results are analyzed in terms of frequency and amplitude of rotation of the flagpole. We report numerous configurations of coupling by frequency lock-in leading to resonance conditions. In the case of strong coupling, high amplitudes of rotation of the flagpole are reported, up to 75°peak-to-peak, over a large range of wind velocities. We also propose to characterize the strength of the coupling with a dimensionless rigidityB, which can be considered as the ratio of the flag bending rigidity to the stiffness of the oscillator.
Strong correlation between boundary layer excitation and hydrofoil eigenmode occur for specific a... more Strong correlation between boundary layer excitation and hydrofoil eigenmode occur for specific angles of attack and Reynolds numbers, resulting in strong tonal noise emissions under certain circumstances. This study aims to analyze the performance of vibration control methods such as truncated trailing edge or boundary layer triggering. The study explores the conditions for hydroelastic trailing edge vibrations on a hydrofoil clamped in a hydrodynamic tunnel, with tests performed for Reynolds numbers up to 1.2 × 10 6 and various angles of attack up to 10°. Experiments were conducted on a clamped 0.1 m chord NACA0015 aluminum hydrofoil, with measurements taken for both vibrations and hydrodynamic components such as lift, drag, and moment. The goal of the study is to closely understand the impact of vibration control on hydrofoil efficiency. This could be very beneficial for those who are working on optimizing profile design. The study first presents the experimental setup, followed by an analysis of the hydrofoil's vibratory response and a presentation of the effectiveness of control solutions. Then, the performance of these solutions are discussed followed by a conclusion.
Address all correspondence to this author1 This paper focuses on the dynamical responses of a two... more Address all correspondence to this author1 This paper focuses on the dynamical responses of a two degrees of freedom flat plate undergoing classical coupled-mode flutter in a wind tunnel at low Reynolds number Rea2.5 104. The flat plate model, at zero angle of attack, was flexibly mounted in heave and pitch in an experimental setup that allow high amplitude oscillations. At the critical velocity associated to the merging of frequencies, the system undergoes an unstable transient behavior before reaching a low amplitude limit-cycle oscillation regime with slow time varying amplitude. For higher velocity the system branches-off to a higher and more stable limit cycle oscillation regime. Amplitudes evolution with the flow velocity along with the phase lags between the pitch and heave response have been measured highlighting a hysteretic behavior in the LCO upper branch. In that context a by-pass transition to high limit cycle oscillations can be observed for hard perturbation below the...
This paper investigates the potential of using an active flow control technique to modify stall f... more This paper investigates the potential of using an active flow control technique to modify stall flutter oscillations of a NACA (National Advisory Committee for Aeronautics) 0015 wing section. Wind tunnel experiments have been performed with a test-rig that provides the elastic degree of freedom in pitch. Measurements of the clean airfoil are taken at preset angles of [Formula: see text], and for Reynolds numbers of [Formula: see text], which reveal the dependency of the stall flutter oscillations to Rec and θ0. Then, flow control experiments are carried out at [Formula: see text] and [Formula: see text]. Two dielectric barrier discharge plasma actuators have been employed simultaneously to exert dual-point excitation to the baseline flow. It is shown that during the upstroke half-cycle, plasma actuation postpones the dynamic stall of the airfoil and increases the maximum pitch angle of the stall flutter cycle. On the downstroke, dual-point excitation effectively improves the rate of...
Les conditions conduisant aux vibrations hydroélastiques de bord de fuite sont étudiées sur un hy... more Les conditions conduisant aux vibrations hydroélastiques de bord de fuite sont étudiées sur un hydrofoil NACA0015 en Aluminium monté en configuration encastrée-libre dans un tunnel hydrodynamique. Les essais ont été menés pour des nombres de Reynolds compris entre 2 × 10 5 et 9 × 10 5 et différents angles d'incidence de 0 à 10°. De la vibrométrie laser a été utilisée pour identifier la réponse vibratoire de l'hydrofoil. De la vélocimétrie par image de particules résolue en temps (TR-PIV) a aussi été utilisée pour caractériser l'écoulement et discuter de l'origine hydrodynamique du phénomène. Ce travail a pour objectif de décrire les différentes configurations conduisant à un couplage fort entre l'écoulement et un mode d'hydrofoil caractérisé par un ventre de vibration au bord de fuite. Des amplitudes de vibration significatives ont ainsi été observées pour des angles d'incidence compris entre 3.5°et 8.5°. L'analyse de l'écoulement de bord de fuite a également révélé que le comportement de la couche limite intrados au niveau du décollement de bord de fuite joue un rôle essentiel dans le mécanisme d'excitation.
HAL (Le Centre pour la Communication Scientifique Directe), Jul 5, 2022
Wind tunnel tests of 2D rough cylinders are presented. The goal is to simulate the alternate vort... more Wind tunnel tests of 2D rough cylinders are presented. The goal is to simulate the alternate vortex shedding in flow regimes encountered in wind engineering applications, where the full scale Reynolds number is larger than the one that can be reproduced in wind tunnel with small scaled models. Measurements are mainly the synchronized unsteady wall pressures on the cylinder which are post processed using bi-orthogonal decompositions. By comparing the small scale results with those from a previous large scale experiment, we show that the technique of rough cylinder is incomplete and can approach roughly global parameters only.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 13, 2022
The present work focuses on flutter mitigation of a flat plate section model using passive linear... more The present work focuses on flutter mitigation of a flat plate section model using passive linear and nonlinear vibration absorbers for a two branches (coupled-mode flutter and stall flutter) post-critical flutter scenario. Experiments have been done in a subsonic wind tunnel using an aeroelastic section model setup. Numerical results have been obtained using an analytical section model for which the pitch-plunge-absorbers equations of motion are combined with a nonlinear unsteady aerodynamic formulation. Without control, the two branches post-critical flutter scenario is well captured by the numerical model. Using linear or non linear vibrations absorbers in plunge, qualitative agreement are found. Adding a non linear absorber in pitch, numerical prediction does not match the one obtained in wind tunnel. This study however confirms that a combination of absorbers in both pitch and plunge is the best solution to delay the critical velocity and that a proper numerical tuning should also help to optimize the LCOs mitigations.
HAL (Le Centre pour la Communication Scientifique Directe), Nov 14, 2011
Temporal simulations are increasingly performed for wind effects analysis of flexible structures.... more Temporal simulations are increasingly performed for wind effects analysis of flexible structures. By comparison with classical techniques such as spectral methods, temporal simulations provide advantage of easily combining different kinds of load, can take nonlinearities into account and are also the only way to reproduce transient behaviours. In that context this study deals with the transient response of a two degrees-of-freedom streamlined bridge deck section submitted to a single gust. Experimental evidence of the potentially high level of transient energy amplification due to that kind of extraneously excitation have been recently demonstrated for an airfoil section [3, 4] and for a streamlined bridge deck section [5], below the critical flutter wind speed. The present study then focuses on the validation of a time-dependant model, based on a simple formulation of both the motion-dependant and buffeting forces, for catching that kind of transient behaviour. A parametric study is done in order to highlight the impact of the pitch-plunge frequency ratio on the energy amplification below the critical flutter wind speed.
HAL (Le Centre pour la Communication Scientifique Directe), Jul 2, 2012
ABSTRACT This paper explores the dynamical response of a two-degree-of-freedom flat plate undergo... more ABSTRACT This paper explores the dynamical response of a two-degree-of-freedom flat plate undergoing classical coupled-mode flutter in a wind tunnel. Tests are performed at low Reynolds number (Re~2.5×104), using an aeroelastic set-up that enables high amplitude pitch–plunge motion. Starting from rest and increasing the flow velocity, an unstable behaviour is first observed at the merging of frequencies: after a transient growth period the system enters a low amplitude limit-cycle oscillation regime with slowly varying amplitude. For higher velocity the system transitions to higher-amplitude and stable limit cycle oscillations (LCO) with amplitude increasing with the flow velocity. Decreasing the velocity from this upper LCO branch the system remains in stable self-sustained oscillations down to 85% of the critical velocity. Starting from rest, the system can also move toward a stable LCO regime if a significant perturbation is imposed. Those results show that both the flutter boundary and post-critical behaviour are affected by nonlinear mechanisms. They also suggest that nonlinear aerodynamic effects play a significant role.
HAL (Le Centre pour la Communication Scientifique Directe), Nov 22, 2015
In the context of energy harvesting we address the coupling between a flexible flag and its flagp... more In the context of energy harvesting we address the coupling between a flexible flag and its flagpole equipped so that it constitutes a spring-mass oscillator. An extensive set of experiments is carried out in wind tunnel for various flag and oscillator parameters. Results are analyzed in terms of frequency and amplitude of rotation of the flagpole. We report numerous configurations of coupling by frequency lock-in leading to resonance conditions. In the case of strong coupling, high amplitudes of rotation of the flagpole are reported, up to 75°peak-to-peak, over a large range of wind velocities. We also propose to characterize the strength of the coupling with a dimensionless rigidityB, which can be considered as the ratio of the flag bending rigidity to the stiffness of the oscillator.
Strong correlation between boundary layer excitation and hydrofoil eigenmode occur for specific a... more Strong correlation between boundary layer excitation and hydrofoil eigenmode occur for specific angles of attack and Reynolds numbers, resulting in strong tonal noise emissions under certain circumstances. This study aims to analyze the performance of vibration control methods such as truncated trailing edge or boundary layer triggering. The study explores the conditions for hydroelastic trailing edge vibrations on a hydrofoil clamped in a hydrodynamic tunnel, with tests performed for Reynolds numbers up to 1.2 × 10 6 and various angles of attack up to 10°. Experiments were conducted on a clamped 0.1 m chord NACA0015 aluminum hydrofoil, with measurements taken for both vibrations and hydrodynamic components such as lift, drag, and moment. The goal of the study is to closely understand the impact of vibration control on hydrofoil efficiency. This could be very beneficial for those who are working on optimizing profile design. The study first presents the experimental setup, followed by an analysis of the hydrofoil's vibratory response and a presentation of the effectiveness of control solutions. Then, the performance of these solutions are discussed followed by a conclusion.
Address all correspondence to this author1 This paper focuses on the dynamical responses of a two... more Address all correspondence to this author1 This paper focuses on the dynamical responses of a two degrees of freedom flat plate undergoing classical coupled-mode flutter in a wind tunnel at low Reynolds number Rea2.5 104. The flat plate model, at zero angle of attack, was flexibly mounted in heave and pitch in an experimental setup that allow high amplitude oscillations. At the critical velocity associated to the merging of frequencies, the system undergoes an unstable transient behavior before reaching a low amplitude limit-cycle oscillation regime with slow time varying amplitude. For higher velocity the system branches-off to a higher and more stable limit cycle oscillation regime. Amplitudes evolution with the flow velocity along with the phase lags between the pitch and heave response have been measured highlighting a hysteretic behavior in the LCO upper branch. In that context a by-pass transition to high limit cycle oscillations can be observed for hard perturbation below the...
This paper investigates the potential of using an active flow control technique to modify stall f... more This paper investigates the potential of using an active flow control technique to modify stall flutter oscillations of a NACA (National Advisory Committee for Aeronautics) 0015 wing section. Wind tunnel experiments have been performed with a test-rig that provides the elastic degree of freedom in pitch. Measurements of the clean airfoil are taken at preset angles of [Formula: see text], and for Reynolds numbers of [Formula: see text], which reveal the dependency of the stall flutter oscillations to Rec and θ0. Then, flow control experiments are carried out at [Formula: see text] and [Formula: see text]. Two dielectric barrier discharge plasma actuators have been employed simultaneously to exert dual-point excitation to the baseline flow. It is shown that during the upstroke half-cycle, plasma actuation postpones the dynamic stall of the airfoil and increases the maximum pitch angle of the stall flutter cycle. On the downstroke, dual-point excitation effectively improves the rate of...
Uploads
Papers by Xavier Amandolese