The Experts below are selected from a list of 3033 Experts worldwide ranked by ideXlab platform
Toshiyuki Nakata - One of the best experts on this subject based on the ideXlab platform.
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A simulation-based study on longitudinal gust response of Flexible flapping Wings
2018Co-Authors: Toshiyuki Nakata, Ryusuke Noda, Shinobu KumagaiAbstract:Winged animals such as insects are capable of flying and surviving in an unsteady and unpredictable aerial environment. They generate and control aerodynamic forces by flapping their Flexible Wings. While the dynamic shape changes of their flapping Wings are known to enhance the efficiency of their flight, they can also affect the stability of a flapping wing flyer under unpredictable disturbances by responding to the sudden changes of aerodynamic forces on the wing. In order to test the hypothesis, the gust response of Flexible flapping Wings is investigated numerically with a specific focus on the passive maintenance of aerodynamic forces by the wing flexibility. The computational model is based on a dynamic flight simulator that can incorporate the realistic morphology, the kinematics, the structural dynamics, the aerodynamics and the fluid–structure interactions of a hovering hawkmoth. The longitudinal gusts are imposed against the tethered model of a hovering hawkmoth with Flexible flapping Wings. It is found that the aerodynamic forces on the flapping Wings are affected by the gust, because of the increase or decrease in relative wingtip velocity or kinematic angle of attack. The passive shape change of Flexible Wings can, however, reduce the changes in the magnitude and direction of aerodynamic forces by the gusts from various directions, except for the downward gust. Such adaptive response of the Flexible structure to stabilise the attitude can be classified into the mechanical feedback, which works passively with minimal delay, and is of great importance to the design of bio-inspired flapping Wings for micro-air vehicles.
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A fluid-structure interaction model of insect flight with Flexible Wings
2012Co-Authors: Toshiyuki NakataAbstract:We present a fluid-structure interactions (FSI) model of insect flapping flight with Flexible Wings. This FSI-based model is established by loosely coupling a finite element method (FEM)-based computational structural dynamic (CSD) model and a computational fluid dynamic (CFD)-based insect dynamic flight simulator. The CSD model is developed specifically for insect flapping flight, which is capable to model thin shell structures of insect Flexible Wings by taking into account the distribution and anisotropy in both wing morphology involving veins, membranes, fibers and density, and in wing material properties of Young's modulus and Poisson's ratios. The insect dynamic flight simulator that is based on a multi-block, overset grid, fortified Navier-Stokes solver is capable to integrate modeling of realistic wing-body morphology, realistic flapping-wing and body kinematics, and unsteady aerodynamics in flapping-wing flights. Validation of the FSI-based aerodynamics and structural dynamics in Flexible Wings is achieved through a set of benchmark tests and comparisons with measurements, which contain a heaving spanwise Flexible wing, a heaving chordwise-Flexible wing with a rigid teardrop element, and a realistic hawkmoth wing rotating in air. A FSI analysis of hawkmoth hovering with flapping Flexible Wings is then carried out and discussed with a specific focus on the in-flight deformation of the hawkmoth Wings and hovering aerodynamic performances with the Flexible and rigid Wings. Our results demonstrate the feasibility of the present FSI model in accurately modeling and quantitatively evaluating Flexible-wing aerodynamics of insect flapping flight in terms of the aerodynamic forces, the power consumption and the efficiency.
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aerodynamic performance of a hovering hawkmoth with Flexible Wings a computational approach
2011Co-Authors: Toshiyuki Nakata, Hao LiuAbstract:Insect Wings are deformable structures that change shape passively and dynamically owing to inertial and aerodynamic forces during flight. It is still unclear how the three-dimensional and passive change of wing kinematics owing to inherent wing flexibility contributes to unsteady aerodynamics and energetics in insect flapping flight. Here, we perform a systematic fluid-structure interaction based analysis on the aerodynamic performance of a hovering hawkmoth, Manduca, with an integrated computational model of a hovering insect with rigid and Flexible Wings. Aerodynamic performance of flapping Wings with passive deformation or prescribed deformation is evaluated in terms of aerodynamic force, power and efficiency. Our results reveal that wing flexibility can increase downwash in wake and hence aerodynamic force: first, a dynamic wing bending is observed, which delays the breakdown of leading edge vortex near the wing tip, responsible for augmenting the aerodynamic force-production; second, a combination of the dynamic change of wing bending and twist favourably modifies the wing kinematics in the distal area, which leads to the aerodynamic force enhancement immediately before stroke reversal. Moreover, an increase in hovering efficiency of the Flexible wing is achieved as a result of the wing twist. An extensive study of wing stiffness effect on aerodynamic performance is further conducted through a tuning of Young's modulus and thickness, indicating that insect wing structures may be optimized not only in terms of aerodynamic performance but also dependent on many factors, such as the wing strength, the circulation capability of wing veins and the control of wing movements.
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micro air vehicle motivated computational biomechanics in bio flights aerodynamics flight dynamics and maneuvering stability
2010Co-Authors: Hao Liu, Masateru Maeda, Hikaru Aono, Na Gao, Toshiyuki Nakata, Wei ShyyAbstract:Aiming at developing an effective tool to unveil key mechanisms in bio-flight as well as to provide guidelines for bio-inspired micro air vehicles (MAVs) design, we propose a comprehensive computational framework, which integrates aerodynamics, flight dynamics, vehicle stability and maneuverability. This framework consists of (1) a Navier–Stokes unsteady aerodynamic model; (2) a linear finite element model for structural dynamics; (3) a fluid-structure interaction (FSI) model for coupled Flexible wing aerodynamics aeroelasticity; (4) a free-flying rigid body dynamic (RBD) model utilizing the Newtonian-Euler equations of 6DoF motion; and (5) flight simulator accounting for realistic wing-body morphology, flapping-wing and body kinematics, and a coupling model accounting for the nonlinear 6DoF flight dynamics and stability of insect flapping flight. Results are presented based on hovering aerodynamics with rigid and Flexible Wings of hawkmoth and fruitfly. The present approach can support systematic analyses of bio- and bio-inspired flight.
Wei Shyy - One of the best experts on this subject based on the ideXlab platform.
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a scaling parameter for the thrust generation of flapping Flexible Wings
2011Co-Authors: Changkwon Kang, Hikaru Aono, Carlos E S Cesnik, Wei ShyyAbstract:Thrust generation and scaling parameters for flapping Flexible Wings are investigated using an integrated framework of computational fluid dynamics and structural dynamics solvers. To explore the influences of the density ratio and the effective stiffness on the thrust generation, surrogate models have been generated for a flapping thin isotropic flat Zimmerman wing in still air at = 1.5×10 3 . Time averaged thrust, bending angle, and twist show qualitatively similar behavior and increased with higher ratio between the density ratio and effective stiffness. Flexibility-induced twisting in the wing promotes the thrust generation. To further investigate the flexibility-induced thrust enhancement, plunging chordwise Flexible airfoils in forward flight at = 9.0×10 3 in water are considered. Time averaged thrust increases with larger airfoil thickness, however the thinnest airfoil responded with degradation in performance when motion frequency becomes high. Finally, unified scaling parameters are proposed based on properly normalized governing equations and give a priori order of magnitude estimation of the time averaged thrust and the degree of fluid-structure coupling. The results show that these scaling parameters, given as combinations of the wing geometry, structural properties, and the motion amplitude and frequency, can be applied for both cases with different motion type, Reynolds number, and the fluid medium.
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micro air vehicle motivated computational biomechanics in bio flights aerodynamics flight dynamics and maneuvering stability
2010Co-Authors: Hao Liu, Masateru Maeda, Hikaru Aono, Na Gao, Toshiyuki Nakata, Wei ShyyAbstract:Aiming at developing an effective tool to unveil key mechanisms in bio-flight as well as to provide guidelines for bio-inspired micro air vehicles (MAVs) design, we propose a comprehensive computational framework, which integrates aerodynamics, flight dynamics, vehicle stability and maneuverability. This framework consists of (1) a Navier–Stokes unsteady aerodynamic model; (2) a linear finite element model for structural dynamics; (3) a fluid-structure interaction (FSI) model for coupled Flexible wing aerodynamics aeroelasticity; (4) a free-flying rigid body dynamic (RBD) model utilizing the Newtonian-Euler equations of 6DoF motion; and (5) flight simulator accounting for realistic wing-body morphology, flapping-wing and body kinematics, and a coupling model accounting for the nonlinear 6DoF flight dynamics and stability of insect flapping flight. Results are presented based on hovering aerodynamics with rigid and Flexible Wings of hawkmoth and fruitfly. The present approach can support systematic analyses of bio- and bio-inspired flight.
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computational aeroelasticity framework for analyzing flapping wing micro air vehicles
2009Co-Authors: Satish Kumar Chimakurthi, Rafael Palacios, Jian Tang, Carlos E S Cesnik, Wei ShyyAbstract:Because of their small size and flight regime, coupling of aerodynamics, structural dynamics, and flight dynamics are critical for micro aerial vehicles. This paper presents a computational framework for simulating structural models of varied fidelity and a Navier-Stokes solver, aimed at simulating flapping and Flexible Wings. The structural model uses either 1) the in-house developed UM/NLABS, which decomposes the equations of 3-D elasticity into cross-sectional and spanwise analyses for slender Wings, or 2) MSC.Marc, which is a commercial finite-element solver capable of modeling geometrically nonlinear structures of arbitrary geometry. The flow solver employs a well-tested pressure-based algorithm implemented in STREAM. A NACA0012 cross-sectional rectangular wing of aspect ratio 3, chord Reynolds number of 3 x 10 4 , and reduced frequency varying from 0.4 to 1.82, with prescribed pure plunge motion is investigated. Both rigid and Flexible wing results are presented, and good agreement between experiment and computation are shown regarding tip displacement and thrust coefficient. Issues related to coupling strategies, fluid physics associated with rigid and Flexible Wings, and implications of fluid density on aerodynamic loading are also explored in this paper.
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Flexible Wings and fluid structure interactions for micro air vehicles
2009Co-Authors: Wei Shyy, Satish Kumar Chimakurthi, Carlos E S Cesnik, Bret Stanford, Yongsheng Lian, Jianing Tang, Peter IfjuAbstract:Aerodynamics, structural dynamics, and flight dynamics of natural flyers intersect with some of the richest problems in micro-air vehicles (MAVs), including massively unsteady three-dimensional separation, transition in boundary and shear layers, vortical flows, unsteady flight environment, aeroelasticity, and adaptive control being just a few examples. A challenge is that the scaling of both fluid dynamics and structural dynamics between smaller natural flyer and practical flying hardware/lab experiment (larger dimension) is fundamentally difficult. The interplay between Flexible structures and aerodynamics motivated by the MAV development is discussed in this chapter. For fixed Wings, membrane materials exhibit self-initiated vibration even in a steady free stream which lowers the effective angle of attack of the membrane structure compared to that of the rigid wing. For flapping Wings, structural flexibility can enhance leading-edge suction via increasing the effective angle of attack, resulting in higher thrust generation.
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computational aeroelasticity framework for analyzing flapping wing micro air vehicles
2008Co-Authors: Rafael Palacios, Wei Shyy, Satish Kumar Chimakurthi, Jian Tang, Carlos E S CesnikAbstract:Due to their small size and flight regime, coupling of aerodynamics, structural dynamics, and flight dynamics is critical for Micro Aerial Vehicles. This paper presents a computational framework for simulating structural models of varied fidelity and a Navier-Stokes solver, aimed at simulating flapping and Flexible Wings. The structural model utilizes either (i) the in-house developed UM/NLABS, which decomposes the equations of 3-D elasticity into cross-sectional and spanwise analyses for slender Wings; or (ii) MSC.Marc, which is a commercial finite element solver capable of modeling geometrically-nonlinear structures of arbitrary geometry. The flow solver employs a well tested pressure-based algorithm implemented in STREAM. A NACA0012 cross-section rectangular wing of aspect ratio 3, chord Reynolds number of 3x10 4 , and reduced frequency varying from 0.4 to 1.82 is investigated. Both rigid and Flexible wing results are presented and good agreement between experiment and computation are shown regarding tip displacement and thrust coefficient. Issues related to coupling strategies, fluid physics associated with rigid and Flexible Wings, and implications of fluid density on aerodynamic loading are also explored in this paper.
Eva Kanso - One of the best experts on this subject based on the ideXlab platform.
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enhanced flight performance in non uniformly Flexible Wings
2020Co-Authors: Lionel Vincent, Min Zheng, John H Costello, Eva KansoAbstract:The flexibility of biological propulsors such as Wings and fins is believed to contribute to the higher performance of flying and swimming animals compared with their engineered peers. Flexibility ...
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enhanced flight performance in non uniformly Flexible Wings
2020Co-Authors: Lionel Vincent, Min Zheng, John H Costello, Eva KansoAbstract:The flexibility of biological propulsors such as Wings and fins is believed to contribute to the higher performance of flying and swimming animals compared with their engineered peers. Flexibility seems to follow a universal design rule that induces bending patterns at about one-third from the distal tip of the propulsor's span. However, the aerodynamic mechanisms that shaped this convergent design and the potential improvement in performance are not well understood. Here we analyze the effect of heterogenous flexibility on the flight performance of tumbling Wings. Using experiments, numerical simulations, and scaling analysis, we demonstrate that spanwise tip flexibility that follows this empirical rule leads to improved flight performance. Our findings attribute this improvement to flutter-induced drag reduction. This mechanism is independent of the wing's auto-rotation and represents a more general trait of Wings with non-uniform tip flexibility. We conclude by analyzing the effects of both spanwise and chordwise non-uniformity on the flight performance of tumbling seedpods.
John H Costello - One of the best experts on this subject based on the ideXlab platform.
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enhanced flight performance in non uniformly Flexible Wings
2020Co-Authors: Lionel Vincent, Min Zheng, John H Costello, Eva KansoAbstract:The flexibility of biological propulsors such as Wings and fins is believed to contribute to the higher performance of flying and swimming animals compared with their engineered peers. Flexibility ...
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enhanced flight performance in non uniformly Flexible Wings
2020Co-Authors: Lionel Vincent, Min Zheng, John H Costello, Eva KansoAbstract:The flexibility of biological propulsors such as Wings and fins is believed to contribute to the higher performance of flying and swimming animals compared with their engineered peers. Flexibility seems to follow a universal design rule that induces bending patterns at about one-third from the distal tip of the propulsor's span. However, the aerodynamic mechanisms that shaped this convergent design and the potential improvement in performance are not well understood. Here we analyze the effect of heterogenous flexibility on the flight performance of tumbling Wings. Using experiments, numerical simulations, and scaling analysis, we demonstrate that spanwise tip flexibility that follows this empirical rule leads to improved flight performance. Our findings attribute this improvement to flutter-induced drag reduction. This mechanism is independent of the wing's auto-rotation and represents a more general trait of Wings with non-uniform tip flexibility. We conclude by analyzing the effects of both spanwise and chordwise non-uniformity on the flight performance of tumbling seedpods.
Fangbao Tian - One of the best experts on this subject based on the ideXlab platform.
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numerical study of Flexible flapping Wings with an immersed boundary method fluid structure acoustics interaction
2019Co-Authors: Li Wang, Fangbao TianAbstract:Abstract The fluid–structure–acoustics interaction of Flexible flapping Wings is numerically studied by using an immersed boundary method at a Mach number of 0.1. In this study, a wing flapping in a uniform flow with prescribed leading edge motion is considered. Apart from rigid Wings, Flexible Wings of various bending rigidities and mass ratios are also examined. By using a direct numerical simulation technique, the sound generation mechanism is identified. The numerical results show that the wing with combined translational and rotational motion generates smaller sounds than the translating wing, and larger rotational angles transform the dipole sound to a monopole one. Similar sound fields are observed among all these Wings, except that the direction of the sound shifts to the downstream for large Flexible Wings. Frequency analysis shows that the sound is dominated by the flapping frequency and two times of the flapping frequency in the vertical and horizontal directions, respectively. The results also show that the thrust increases first then decreases with bending rigidity for all three mass ratios considered, and the lighter wing suffers more decrease. However, the fluctuating pressure for the three mass ratios varies significantly. Specifically, it increases significantly with the decreasing bending rigidity when the structural inertia is dominating at m ∗ = 5 . 0 ; but it experiences a reduction contrarily when the aerodynamics becomes dominant at m ∗ = 0 . 5 ; for the medium mass ratio at m ∗ = 1 . 0 , no significant effects are observed. The comparisons indicate that the Flexible wing with a lower mass ratio (e.g. m ∗ = 0 . 5 ) and a medium flexibility (e.g. ω ∗ = 0 . 3 ) achieves lower sound generation without significant thrust decrease. In addition, the sound on the windward side is pronounced significantly when the wing is flapping with a stroke plane angle less than 9 0 o . The present results can expand the currently limited database of fluid–structure–acoustics interaction, and also provide an insight for the optimization of flight vehicle using flapping wing.