The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Dimitriadis Grigorios - One of the best experts on this subject based on the ideXlab platform.
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Flutter behaviour of aerodynamically coupled cantilever wings
2020Co-Authors: Dooner Dylan, Vio Gareth, Dimitriadis GrigoriosAbstract:audience: researcher, professionalFlutter and divergence behaviour for discrete bodies in the farfield has long been considered, such as in wing-empennage interaction but not for long, slender bodies in a non-rotating frame (like that encountered in wind turbines). This work focuses on filling that knowledge gap. As such, flutter behaviour has been determined for flat plates of varying planforms in various combinations and configured either in parallel or in series. A dimensionless separation parameter based upon the chord has been selected. A closed form state-space model for the nonlinear aeroelastic response of thin cantilevered flat plates has been derived using a combination of the MSC.NASTRAN commercial structural solver and a linearised continuous time vortex lattice aerodynamic model with an image inspired cascade. The modal-based model is solved for the amplitude and period of the limit cycles of the flat plates using numerical continuation. These results are compared to experimental data obtained from identical flat plates in a wind tunnel
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Flutter behaviour of aerodynamically coupled cantilever wings
2020Co-Authors: Dooner Dylan, Vio Gareth, Dimitriadis GrigoriosAbstract:Flutter and divergence behaviour for discrete bodies in the farfield has long been considered, such as in wing-empennage interaction but not for long, slender bodies in a non-rotating frame (like that encountered in wind turbines). This work focuses on filling that knowledge gap. As such, flutter behaviour has been determined for flat plates of varying planforms in various combinations and configured either in parallel or in series. A dimensionless separation parameter based upon the chord has been selected. A closed form state-space model for the nonlinear aeroelastic response of thin cantilevered flat plates has been derived using a combination of the MSC.NASTRAN commercial structural solver and a linearised continuous time vortex lattice aerodynamic model with an image inspired cascade. The modal-based model is solved for the amplitude and period of the limit cycles of the flat plates using numerical continuation. These results are compared to experimental data obtained from identical flat plates in a wind tunnel
Rafael Palacios - One of the best experts on this subject based on the ideXlab platform.
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t tail flutter potential flow modelling experimental validation and flight tests
Progress in Aerospace Sciences, 2014Co-Authors: Joseba Murua, Pablo Martinez, Hector Climent, Louw Van Zyl, Rafael PalaciosAbstract:© 2014 Elsevier Ltd.Flutter of T-tail configurations is caused by the aeroelastic coupling between the vertical fin and the horizontal stabiliser. The latter is mounted on the fin instead of the fuselage, and hence the arrangement presents distinct characteristics compared to other typical empennage setups; specifically, T-tail aeroelasticity is governed by inplane dynamics and steady aerodynamic loading, which are typically not included in flutter clearance methodologies based on the doublet lattice method. As the number of new aircraft featuring this tail configuration increases, there is a need for precise understanding of the phenomenon, appropriate tools for its prediction, and reliable benchmarking data. This paper addresses this triple challenge by providing a detailed explanation of T-tail flutter physics, describing potential-flow modelling alternatives, and presenting detailed numerical and experimental results to compensate for the shortage of reproducible data in the literature. A historical account of the main milestones in T-tail aircraft development is included, followed by a T-tail flutter research review that emphasises the latest contributions from industry as well as academia. The physical problem is dissected next, highlighting the individual and combined effects that drive the phenomenon. Three different methodologies, all based on potential-flow aerodynamics, are considered for T-tail subsonic flutter prediction: (i) direct incorporation of supplementary T-tail effects as additional terms in the flutter equations; (ii) a generalisation of the boundary conditions and air loads calculation on the double lattice; and (iii) a linearisation of the unsteady vortex lattice method with arbitrary kinematics. Comparison with wind-tunnel experimental results evidences that all three approaches are consistent and capture the key characteristics in the T-tail dynamics. The validated numerical models are then exercised in easy-to-duplicate canonical test cases. These parametric studies illustrate the impact of well-known factors in T-tail flutter, namely horizontal tailplane dihedral, flexibility and static deformations. In addition, scenarios are exposed in which the stability behaviour is dictated by typically second-order effects, such as chordwise forces and quadratic modes, revealing drastically different qualitative flutter curves. It is also shown that there is a distinction between angle of attack of the whole tail assembly and incidence of the horizontal tailplane relative to the fin, which might yield very counterintuitive trends depending on the configuration parameters. The paper concludes with flight test results of the Airbus A400M, epitome of modern T-tail aircraft. Tests performed in a wake-vortex encounter campaign complement the virtually nonexistent literature in the topic, demonstrate how T-tail effects can be measured in flight and restate the adequacy of potential-flow models for T-tail flutter prediction.
Agostino De Marco - One of the best experts on this subject based on the ideXlab platform.
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Aircraft directional stability and vertical tail design: A review of semi-empirical methods
Progress in Aerospace Sciences, 2017Co-Authors: Danilo Ciliberti, Pierluigi Della Vecchia, Fabrizio Nicolosi, Agostino De MarcoAbstract:Aircraft directional stability and control are related to vertical tail design. The safety, performance, and flight qualities of an aircraft also depend on a correct empennage sizing. Specifically, the vertical tail is responsible for the aircraft yaw stability and control. If these characteristics are not well balanced, the entire aircraft design may fail. Stability and control are often evaluated, especially in the preliminary design phase, with semi-empirical methods, which are based on the results of experimental investigations performed in the past decades, and occasionally are merged with data provided by theoretical assumptions. This paper reviews the standard semi-empirical methods usually applied in the estimation of airplane directional stability derivatives in preliminary design, highlighting the advantages and drawbacks of these approaches that were developed from wind tunnel tests performed mainly on fighter airplane configurations of the first decades of the past century, and discussing their applicability on current transport aircraft configurations. Recent investigations made by the authors have shown the limit of these methods, proving the existence of aerodynamic interference effects in sideslip conditions which are not adequately considered in classical formulations. The article continues with a concise review of the numerical methods for aerodynamics and their applicability in aircraft design, highlighting how Reynolds-Averaged Navier-Stokes (RANS) solvers are well-suited to attain reliable results in attached flow conditions, with reasonable computational times. From the results of RANS simulations on a modular model of a representative regional turboprop airplane layout, the authors have developed a modern method to evaluate the vertical tail and fuselage contributions to aircraft directional stability. The investigation on the modular model has permitted an effective analysis of the aerodynamic interference effects by moving, changing, and expanding the available airplane components. Wind tunnel tests over a wide range of airplane configurations have been used to validate the numerical approach. The comparison between the proposed method and the standard semi-empirical methods available in literature proves the reliability of the innovative approach, according to the available experimental data collected in the wind tunnel test campaign.
Dooner Dylan - One of the best experts on this subject based on the ideXlab platform.
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Flutter behaviour of aerodynamically coupled cantilever wings
2020Co-Authors: Dooner Dylan, Vio Gareth, Dimitriadis GrigoriosAbstract:audience: researcher, professionalFlutter and divergence behaviour for discrete bodies in the farfield has long been considered, such as in wing-empennage interaction but not for long, slender bodies in a non-rotating frame (like that encountered in wind turbines). This work focuses on filling that knowledge gap. As such, flutter behaviour has been determined for flat plates of varying planforms in various combinations and configured either in parallel or in series. A dimensionless separation parameter based upon the chord has been selected. A closed form state-space model for the nonlinear aeroelastic response of thin cantilevered flat plates has been derived using a combination of the MSC.NASTRAN commercial structural solver and a linearised continuous time vortex lattice aerodynamic model with an image inspired cascade. The modal-based model is solved for the amplitude and period of the limit cycles of the flat plates using numerical continuation. These results are compared to experimental data obtained from identical flat plates in a wind tunnel
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Flutter behaviour of aerodynamically coupled cantilever wings
2020Co-Authors: Dooner Dylan, Vio Gareth, Dimitriadis GrigoriosAbstract:Flutter and divergence behaviour for discrete bodies in the farfield has long been considered, such as in wing-empennage interaction but not for long, slender bodies in a non-rotating frame (like that encountered in wind turbines). This work focuses on filling that knowledge gap. As such, flutter behaviour has been determined for flat plates of varying planforms in various combinations and configured either in parallel or in series. A dimensionless separation parameter based upon the chord has been selected. A closed form state-space model for the nonlinear aeroelastic response of thin cantilevered flat plates has been derived using a combination of the MSC.NASTRAN commercial structural solver and a linearised continuous time vortex lattice aerodynamic model with an image inspired cascade. The modal-based model is solved for the amplitude and period of the limit cycles of the flat plates using numerical continuation. These results are compared to experimental data obtained from identical flat plates in a wind tunnel
Joseba Murua - One of the best experts on this subject based on the ideXlab platform.
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t tail flutter potential flow modelling experimental validation and flight tests
Progress in Aerospace Sciences, 2014Co-Authors: Joseba Murua, Pablo Martinez, Hector Climent, Louw Van Zyl, Rafael PalaciosAbstract:© 2014 Elsevier Ltd.Flutter of T-tail configurations is caused by the aeroelastic coupling between the vertical fin and the horizontal stabiliser. The latter is mounted on the fin instead of the fuselage, and hence the arrangement presents distinct characteristics compared to other typical empennage setups; specifically, T-tail aeroelasticity is governed by inplane dynamics and steady aerodynamic loading, which are typically not included in flutter clearance methodologies based on the doublet lattice method. As the number of new aircraft featuring this tail configuration increases, there is a need for precise understanding of the phenomenon, appropriate tools for its prediction, and reliable benchmarking data. This paper addresses this triple challenge by providing a detailed explanation of T-tail flutter physics, describing potential-flow modelling alternatives, and presenting detailed numerical and experimental results to compensate for the shortage of reproducible data in the literature. A historical account of the main milestones in T-tail aircraft development is included, followed by a T-tail flutter research review that emphasises the latest contributions from industry as well as academia. The physical problem is dissected next, highlighting the individual and combined effects that drive the phenomenon. Three different methodologies, all based on potential-flow aerodynamics, are considered for T-tail subsonic flutter prediction: (i) direct incorporation of supplementary T-tail effects as additional terms in the flutter equations; (ii) a generalisation of the boundary conditions and air loads calculation on the double lattice; and (iii) a linearisation of the unsteady vortex lattice method with arbitrary kinematics. Comparison with wind-tunnel experimental results evidences that all three approaches are consistent and capture the key characteristics in the T-tail dynamics. The validated numerical models are then exercised in easy-to-duplicate canonical test cases. These parametric studies illustrate the impact of well-known factors in T-tail flutter, namely horizontal tailplane dihedral, flexibility and static deformations. In addition, scenarios are exposed in which the stability behaviour is dictated by typically second-order effects, such as chordwise forces and quadratic modes, revealing drastically different qualitative flutter curves. It is also shown that there is a distinction between angle of attack of the whole tail assembly and incidence of the horizontal tailplane relative to the fin, which might yield very counterintuitive trends depending on the configuration parameters. The paper concludes with flight test results of the Airbus A400M, epitome of modern T-tail aircraft. Tests performed in a wake-vortex encounter campaign complement the virtually nonexistent literature in the topic, demonstrate how T-tail effects can be measured in flight and restate the adequacy of potential-flow models for T-tail flutter prediction.