The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Veldhuis L.l.m. - One of the best experts on this subject based on the ideXlab platform.
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Breakdown of aerodynamic interactions for the lateral rotors on a compound helicopter
'Elsevier BV', 2020Co-Authors: Stokkermans T.c.a., Veldhuis L.l.m., Soemarwoto Bambang, Fukari Raphaël, Eglin PaulAbstract:Auxiliary lift and/or thrust on a compound helicopter can introduce complex aerodynamic interactions between the auxiliary lift and thrust components and the main rotor. In this study high-fidelity computational fluid dynamics analyses were performed to capture the various aerodynamic interactions which are occurring for the Airbus RACER compound helicopter, featuring a box-wing design for auxiliary lift in cruise and wingtip-mounted lateral rotors in pusher configuration for auxiliary thrust in cruise and counter-torque in hover. Although the study was limited to a specific geometry, the effects and phenomena are expected to be to some extent applicable in general for compound helicopters and wingtip-mounted rotors in pusher configuration. A quantitative indication of the aerodynamic interaction effects could be established by leaving away different airframe components in the simulations. The downwash of the main rotor was found to cause a small negative angle of attack in cruise for the wings and lateral rotors and impinged directly on the lateral rotors in hover, resulting in moderate to very significant sinusoidally varying blade loading. The wing increased lateral rotor propulsive efficiency in cruise through its wingtip rotational flowfield and to a lesser extent through its wake. An upstream effect of the lateral rotors on the wing loading was also found. In hover the wing caused a net increase in left lateral rotor thrust as the deflection of the main rotor flow towards the rotor resulted in a local thrust decrease and the low momentum inflow to the rotor from the wake of the wing resulted in a local thrust increase. A small thrust decrease for the right lateral rotor was found due to the wing disturbing its slipstream as this rotor produced reversed thrust. In general, very significant aerodynamic interaction effects can be expected when a main rotor, lateral rotors and wing are in proximity to each other.Flight Performance and Propulsio
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Analysis and Design of a Small-ScaleWingtip-Mounted Pusher Propeller
'American Institute of Aeronautics and Astronautics (AIAA)', 2019Co-Authors: Stokkermans T.c.a., As Nootebos, Veldhuis L.l.m.Abstract:The wingtip-mounted pusher propeller, which experiences a performance benefit from the interaction with the wingtip flowfield, is an interesting concept for distributed propulsion. This paper examines a propeller design framework and provides verification with RANS CFD simulations by analyzing the wing of a 9-passenger commuter airplane with a wingtip-mounted propeller in pusher configuration. In the taken approach, a wingtip flowfield is extracted from a CFD simulation, circumferentially averaged and provided to a lower order propeller analysis and optimisation routine. Possible propulsive efficiency gains for the propeller due to installation are significant, up to 16% increase at low thrust levels, decreasing to approximately 7:5% at the highest thrust level, for a range of thrust from 5% up to 100% of the wing drag. These gains are found to be independent of propeller radius for thrust levels larger than 30% of the wing drag. Effctively, the propeller geometry is optimized for the required thrust and to a lesser degree for the non-uniformity in the flowfield. Propeller blade optimization and installation result in higher profile eciency in the blade root sections and a more inboard thrust distribution.Flight Performance and Propulsio
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Wingtip-Mounted Propellers: Aerodynamic Analysis of Interaction Effects and Comparison with Conventional Layout
'American Institute of Aeronautics and Astronautics (AIAA)', 2019Co-Authors: Sinnige T., Stokkermans T.c.a., Van Arnhem N., Eitelberg G., Veldhuis L.l.m.Abstract:Wingtip-mounted propellers installed in a tractor configuration can decrease the wing induced drag by attenuating the wingtip vortex by the propeller slipstream. This paper presents an aerodynamic analysis of the propeller-wing interaction effects for the wingtip-mounted propeller configuration, including a comparison with a conventional configuration with the propeller mounted on the inboard part of the wing. Measurements were taken in a low-speed wind tunnel at Delft University of Technology, with two wing models and a low-speed propeller. Particle-image-velocimetry measurements downstream of a symmetric wing with integrated flap highlighted the swirl reductions characteristic of the wingtip-mounted propeller due to wingtip-vortex attenuation and swirl recovery. External-balance and surface-pressure measurements confirmed that this led to an induced-drag reduction with inboard-up propeller rotation. In a direct comparison with a conventional propeller-wing layout, the wingtip-mounted configuration showed a drag reduction of around 15% at a lift coefficient of 0.5 and a thrust coefficient of 0.12. This aerodynamic benefit increased upon increasing the wing lift coefficient and propeller thrust setting. An analysis of the wing performance showed that the aerodynamic benefit of the wingtip-mounted propeller was due to an increase of the wing's effective span-efficiency parameter.Flight Performance and Propulsio
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Wingtip-Mounted Propellers: Aerodynamic Analysis of Interaction Effects and Comparison with Conventional Layout
2019Co-Authors: Sinnige T., Stokkermans T.c.a., Van Arnhem N., Eitelberg G., Veldhuis L.l.m.Abstract:Wingtip-mounted propellers installed in a tractor configuration can decrease the wing induced drag by attenuating the wingtip vortex by the propeller slipstream. This paper presents an aerodynamic analysis of the propeller-wing interaction effects for the wingtip-mounted propeller configuration, including a comparison with a conventional configuration with the propeller mounted on the inboard part of the wing. Measurements were taken in a low-speed wind tunnel at Delft University of Technology, with two wing models and a low-speed propeller. Particle-image-velocimetry measurements downstream of a symmetric wing with integrated flap highlighted the swirl reductions characteristic of the wingtip-mounted propeller due to wingtip-vortex attenuation and swirl recovery. External-balance and surface-pressure measurements confirmed that this led to an induced-drag reduction with inboard-up propeller rotation. In a direct comparison with a conventional propeller-wing layout, the wingtip-mounted configuration showed a drag reduction of around 15% at a lift coefficient of 0.5 and a thrust coefficient of 0.12. This aerodynamic benefit increased upon increasing the wing lift coefficient and propeller thrust setting. An analysis of the wing performance showed that the aerodynamic benefit of the wingtip-mounted propeller was due to an increase of the wing's effective span-efficiency parameter.
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Aerodynamic Performance of a Wingtip-Mounted Tractor Propeller Configuration in Windmilling and Energy-Harvesting Conditions
'American Institute of Aeronautics and Astronautics (AIAA)', 2019Co-Authors: Sinnige T., Stokkermans T.c.a., Van Arnhem N., Veldhuis L.l.m.Abstract:Wingtip-mounted tractor propellers enhance aerodynamic performance by attenuating the wingtip vortex with the propeller slipstream and inducing a favorable upwash on the wing. However, the close coupling between propeller and wing means that wing performance may be degraded when the propeller produces negative thrust. This paper analyzes the aerodynamic interaction eects due to the wingtip-mounted propeller under such conditions, that occur when the propeller is windmilling or used for energy harvesting. Experiments in a low-speed wind tunnel and simulations with a RANS solver highlighted the drop in wing performance at negative thrust for the case with inboard-up rotation. The interaction phenomena are reversed compared to the beneficial propulsive case, since the inflow velocity and angle of attack are now reduced on the part of the wing washed by the slipstream. Because of the reversal of the swirl in the slipstream at negative thrust, the interaction is then favorable with outboard-up rotation. For the considered propeller, that was not optimized for operation at negative thrust, the energy-harvesting efficiency was about 10%. This can be improved for future designs by optimizing the blade geometry and pitch setting of the propeller. Flight Performance and Propulsio
Peiqing Liu - One of the best experts on this subject based on the ideXlab platform.
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near field wingtip vortex characteristics of a rectangular wing in ground effect
54th AIAA Aerospace Sciences Meeting, 2016Co-Authors: Ramesh K Agarwal, Liewei Huang, Peiqing LiuAbstract:The aerodynamics and near-field wingtip vortex characteristics of a rectangular wing with NACA4412 section in ground effect (GE) are studied in this paper. The steady compressible Reynolds-Averaged Navier-Stokes (RANS) equations with the SpalartAllmaras (SA) turbulence model are discretized using the finite volume method. Based on the pressure and lift variations in GE, a 3D rectangular wing can be divided into two parts along the span-wise direction: the quasi-2D inner part of the wing (away from wing tip) in which the lift increases monotonously, and the second part near the wingtip in which the lift decreases. In GE, the wingtip vortex moves outward along the span-wise direction due to the ground mirror effect, and rebounds in the vertical direction due to the induction from the secondary vortex generated from the ground boundary layer. In GE, the strength of the near-field wingtip vortex along the flow direction depends not only on the initial vortex strength and the shear layer developing from the trailing edge of the wing, but also due to the generation of secondary vortex in the ground boundary layer, and the interaction between the wingtip vortex and the secondary vortex.
Shankar Sastry - One of the best experts on this subject based on the ideXlab platform.
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model identification and attitude control scheme for a micromechanical flying insect
International Conference on Control Automation Robotics and Vision, 2002Co-Authors: Xinyan Deng, Luca Schenato, Shankar SastryAbstract:This paper describes recent development on the design of the flight control system for a micromechanical flying insect (MFI), a 10-25 mm (wingtip-to-wingtip) device capable of sustained autonomous flight. High level attitude control is considered. Based on our previous work, in which the complex time-varying component of aerodynamic forces are treated as external disturbances, a nominal state-space linear time-invariant model in hover is developed through linear estimation. The identified model is validated through the virtual insect flight simulator (VIFS), and is used to design feedback controllers for the MFI. A LQG controller is designed and compared with a PD controller. The identification scheme provides a more systematic way of treating aerodynamic modeling errors, and the controllers designed based on the identified model shows better overall performance in simulation. Another advantage of this approach is that measurement of the instantaneous aerodynamic forces is not necessary, thus simplifies the experimental setup for the real MFI.
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hovering flight for a micromechanical flying insect modeling and robust control synthesis
IFAC Proceedings Volumes, 2002Co-Authors: Luca Schenato, Xinyan Deng, Shankar SastryAbstract:Abstract This paper describes recent results on the design and simulation of a flight control strategy for the Micromechanical Flying Insect (MFI), a 10-25mm (wingtip-to-wingtip) device capable of sustained autonomous flight. Biologically inspired by the real insect's flight maneuver, position control is achieved via attitude control. The wings motion is parameterized by a small set of parameters which are sufficient to generate desired average torques to regulate its attitude. Position control is achieved through attitude control based on the linearized dynamics under small angle assumption near hovering. At the end of each wingbeat, the controller schedules the desired wings motion parameters according to state feedback errors. With respect to our previous work (Deng et al. , 2001), we explicitly included the modeling approximations into the design of the flight controller. These errors include the time-varying nature of aerodynamic forces, the input saturation and linearization errors. The proposed controller was simulated with the Virtual Insect Flight Simulator, and the results show improved performance in both position and orientation stabilization.
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hovering flight control of a micromechanical flying insect
Conference on Decision and Control, 2001Co-Authors: Xinyan Deng, Luca Schenato, Shankar SastryAbstract:This paper describes recent results on the design and simulation of a flight control strategy for the micromechanical flying insect (MFI), a 10-25 mm (wingtip-to-wingtip) device capable of sustained autonomous flight. Biologically inspired by the real insect's flight maneuver, the wing kinematics are paremetrized by a small set of parameters which are sufficient to generate desired average torques to regulate its attitude. Position control was achieved through attitude control based on the linearized dynamics under small angle assumption near hovering. During its continuous flight, the controller schedules the desired wing kinematic parameters according to the inverse map based on the feedback error at the end of each wingbeat. The proposed controller was simulated with the Virtual Insect Flight Simulator, and the results show convergence of both position and orientation.
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flight control system for a micromechanical flying insect architecture and implementation
International Conference on Robotics and Automation, 2001Co-Authors: Luca Schenato, Xinyan Deng, Shankar SastryAbstract:Describes results on the design and simulation of a flight control system for the micromechanical flying insect (MFI), a 10-25 mm (wingtip-to-wingtip) device eventually capable of sustained autonomous flight. The biologically inspired system architecture results in a hierarchical structure of different control methodologies, which give the possibility to plan complex missions from a sequence of simple flight modes and maneuvers. As a case study, a stabilizing hovering control scheme is presented and simulated with VIFS, a software simulator for insect flight.
Rafic Ajaj - One of the best experts on this subject based on the ideXlab platform.
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a parametric study on the aeroelasticity of flared hinge folding Wingtips
Aerospace, 2021Co-Authors: Rafic Ajaj, Erick Saavedra I Flores, Mohammadreza Amoozgar, Jonathan CooperAbstract:This paper presents a parametric study on the aeroelasticity of cantilever wings equipped with Flared Hinge Folding Wingtips (FHFWTs). The finite element method is utilized to develop a computational, low-fidelity aeroelastic model. The wing structure is modelled using Euler–Bernoulli beam elements, and unsteady Theodorsen’s aerodynamic strip Theory is used for aerodynamic load predictions. The PK method is used to estimate the aeroelastic boundaries. The model is validated using three rectangular, cantilever wings whose properties are available in literature. Then, a rectangular, cantilever wing is used to study the effect of folding Wingtips on the aeroelastic response and stability boundaries. Two scenarios are considered for the aeroelastic analysis. In the first scenario, the baseline, rectangular wing is split into inboard and outboard segments connected by a flared hinge that allows the outboard segment to fold. In the second scenario, a folding wingtip is added to the baseline wing. For both scenarios, the influence of fold angle, hinge-line angle (flare angle), hinge stiffness, tip mass and geometry are assessed. In addition, the load alleviation capability of FHFWT is evaluated when the wing encounters discrete (1-cosine) gusts. Finally, the hinge is assumed to exhibit cubic nonlinear behavior in torsion, and the effect of nonlinearity on the aeroelastic response is assessed and analyzed for three different cases.
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Flight Dynamics of Transport Aircraft Equipped with Flared-Hinge Folding Wingtips
Journal of Aircraft, 2021Co-Authors: Rafic AjajAbstract:This paper studies the influence of flared-hinge folding Wingtips on the aerodynamic derivatives and flight dynamics of a narrow-body transport aircraft. In addition, the influence of fold angle, h...
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Flight Dynamics and Control Using Folding Wingtips: An Experimental Study
Aerospace, 2017Co-Authors: Josh Mills, Rafic AjajAbstract:This paper presents an experimental investigation on using FOLDing Wingtips sERving as cONtrol effectorS (FOLDERONS) for a mini Unmanned Aerial Vehicle (UAV). A representative off-the-shelf mini-UAV with a conventional configuration was selected. The main theme of this paper is to utilise FOLDERONS as a control effector (mainly in roll) to augment the control authority of conventional control surfaces. Furthermore, the impact of actuation rate on the effectiveness of FOLDERONS is assessed. The paper describes the preliminary and detailed design and sizing of the morphing wing. In addition, the manufacturing of the wing system and its integration with the UAV are addressed. Wind-tunnel testing in the RJ Mitchell wind-tunnel at the University of Southampton was performed. Both static (straight and sideslip) and dynamic (straight flight) tests are conducted at a range of airspeeds and Angles Of Attack (AOAs). The impact of folding Wingtips on the lateral and directional stability is analysed. The main finding of this paper is that FOLDERONS are effective (especially at large dynamic pressure and AOAs) in controlling the lateral and directional stability. Finally, this study shows that FOLDERONS cannot fully replace conventional ailerons especially at low dynamic pressures, and their strong dependence on the AOA makes them prone to a roll reversal phenomena when the wing (and FOLDERONS) is operating at negative AOAs.
Stokkermans T.c.a. - One of the best experts on this subject based on the ideXlab platform.
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Breakdown of aerodynamic interactions for the lateral rotors on a compound helicopter
'Elsevier BV', 2020Co-Authors: Stokkermans T.c.a., Veldhuis L.l.m., Soemarwoto Bambang, Fukari Raphaël, Eglin PaulAbstract:Auxiliary lift and/or thrust on a compound helicopter can introduce complex aerodynamic interactions between the auxiliary lift and thrust components and the main rotor. In this study high-fidelity computational fluid dynamics analyses were performed to capture the various aerodynamic interactions which are occurring for the Airbus RACER compound helicopter, featuring a box-wing design for auxiliary lift in cruise and wingtip-mounted lateral rotors in pusher configuration for auxiliary thrust in cruise and counter-torque in hover. Although the study was limited to a specific geometry, the effects and phenomena are expected to be to some extent applicable in general for compound helicopters and wingtip-mounted rotors in pusher configuration. A quantitative indication of the aerodynamic interaction effects could be established by leaving away different airframe components in the simulations. The downwash of the main rotor was found to cause a small negative angle of attack in cruise for the wings and lateral rotors and impinged directly on the lateral rotors in hover, resulting in moderate to very significant sinusoidally varying blade loading. The wing increased lateral rotor propulsive efficiency in cruise through its wingtip rotational flowfield and to a lesser extent through its wake. An upstream effect of the lateral rotors on the wing loading was also found. In hover the wing caused a net increase in left lateral rotor thrust as the deflection of the main rotor flow towards the rotor resulted in a local thrust decrease and the low momentum inflow to the rotor from the wake of the wing resulted in a local thrust increase. A small thrust decrease for the right lateral rotor was found due to the wing disturbing its slipstream as this rotor produced reversed thrust. In general, very significant aerodynamic interaction effects can be expected when a main rotor, lateral rotors and wing are in proximity to each other.Flight Performance and Propulsio
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Analysis and Design of a Small-ScaleWingtip-Mounted Pusher Propeller
'American Institute of Aeronautics and Astronautics (AIAA)', 2019Co-Authors: Stokkermans T.c.a., As Nootebos, Veldhuis L.l.m.Abstract:The wingtip-mounted pusher propeller, which experiences a performance benefit from the interaction with the wingtip flowfield, is an interesting concept for distributed propulsion. This paper examines a propeller design framework and provides verification with RANS CFD simulations by analyzing the wing of a 9-passenger commuter airplane with a wingtip-mounted propeller in pusher configuration. In the taken approach, a wingtip flowfield is extracted from a CFD simulation, circumferentially averaged and provided to a lower order propeller analysis and optimisation routine. Possible propulsive efficiency gains for the propeller due to installation are significant, up to 16% increase at low thrust levels, decreasing to approximately 7:5% at the highest thrust level, for a range of thrust from 5% up to 100% of the wing drag. These gains are found to be independent of propeller radius for thrust levels larger than 30% of the wing drag. Effctively, the propeller geometry is optimized for the required thrust and to a lesser degree for the non-uniformity in the flowfield. Propeller blade optimization and installation result in higher profile eciency in the blade root sections and a more inboard thrust distribution.Flight Performance and Propulsio
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Wingtip-Mounted Propellers: Aerodynamic Analysis of Interaction Effects and Comparison with Conventional Layout
'American Institute of Aeronautics and Astronautics (AIAA)', 2019Co-Authors: Sinnige T., Stokkermans T.c.a., Van Arnhem N., Eitelberg G., Veldhuis L.l.m.Abstract:Wingtip-mounted propellers installed in a tractor configuration can decrease the wing induced drag by attenuating the wingtip vortex by the propeller slipstream. This paper presents an aerodynamic analysis of the propeller-wing interaction effects for the wingtip-mounted propeller configuration, including a comparison with a conventional configuration with the propeller mounted on the inboard part of the wing. Measurements were taken in a low-speed wind tunnel at Delft University of Technology, with two wing models and a low-speed propeller. Particle-image-velocimetry measurements downstream of a symmetric wing with integrated flap highlighted the swirl reductions characteristic of the wingtip-mounted propeller due to wingtip-vortex attenuation and swirl recovery. External-balance and surface-pressure measurements confirmed that this led to an induced-drag reduction with inboard-up propeller rotation. In a direct comparison with a conventional propeller-wing layout, the wingtip-mounted configuration showed a drag reduction of around 15% at a lift coefficient of 0.5 and a thrust coefficient of 0.12. This aerodynamic benefit increased upon increasing the wing lift coefficient and propeller thrust setting. An analysis of the wing performance showed that the aerodynamic benefit of the wingtip-mounted propeller was due to an increase of the wing's effective span-efficiency parameter.Flight Performance and Propulsio
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Wingtip-Mounted Propellers: Aerodynamic Analysis of Interaction Effects and Comparison with Conventional Layout
2019Co-Authors: Sinnige T., Stokkermans T.c.a., Van Arnhem N., Eitelberg G., Veldhuis L.l.m.Abstract:Wingtip-mounted propellers installed in a tractor configuration can decrease the wing induced drag by attenuating the wingtip vortex by the propeller slipstream. This paper presents an aerodynamic analysis of the propeller-wing interaction effects for the wingtip-mounted propeller configuration, including a comparison with a conventional configuration with the propeller mounted on the inboard part of the wing. Measurements were taken in a low-speed wind tunnel at Delft University of Technology, with two wing models and a low-speed propeller. Particle-image-velocimetry measurements downstream of a symmetric wing with integrated flap highlighted the swirl reductions characteristic of the wingtip-mounted propeller due to wingtip-vortex attenuation and swirl recovery. External-balance and surface-pressure measurements confirmed that this led to an induced-drag reduction with inboard-up propeller rotation. In a direct comparison with a conventional propeller-wing layout, the wingtip-mounted configuration showed a drag reduction of around 15% at a lift coefficient of 0.5 and a thrust coefficient of 0.12. This aerodynamic benefit increased upon increasing the wing lift coefficient and propeller thrust setting. An analysis of the wing performance showed that the aerodynamic benefit of the wingtip-mounted propeller was due to an increase of the wing's effective span-efficiency parameter.
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Aerodynamic Performance of a Wingtip-Mounted Tractor Propeller Configuration in Windmilling and Energy-Harvesting Conditions
'American Institute of Aeronautics and Astronautics (AIAA)', 2019Co-Authors: Sinnige T., Stokkermans T.c.a., Van Arnhem N., Veldhuis L.l.m.Abstract:Wingtip-mounted tractor propellers enhance aerodynamic performance by attenuating the wingtip vortex with the propeller slipstream and inducing a favorable upwash on the wing. However, the close coupling between propeller and wing means that wing performance may be degraded when the propeller produces negative thrust. This paper analyzes the aerodynamic interaction eects due to the wingtip-mounted propeller under such conditions, that occur when the propeller is windmilling or used for energy harvesting. Experiments in a low-speed wind tunnel and simulations with a RANS solver highlighted the drop in wing performance at negative thrust for the case with inboard-up rotation. The interaction phenomena are reversed compared to the beneficial propulsive case, since the inflow velocity and angle of attack are now reduced on the part of the wing washed by the slipstream. Because of the reversal of the swirl in the slipstream at negative thrust, the interaction is then favorable with outboard-up rotation. For the considered propeller, that was not optimized for operation at negative thrust, the energy-harvesting efficiency was about 10%. This can be improved for future designs by optimizing the blade geometry and pitch setting of the propeller. Flight Performance and Propulsio
