scholarly journals Unsteady aerodynamics of flexible wings in transverse gusts

2022 ◽  
Vol 108 ◽  
pp. 103425
Author(s):  
Fidel Fernandez ◽  
David Cleaver ◽  
Ismet Gursul
Keyword(s):  
Unsteady Aerodynamics ◽  
Flexible Wings

scholarly journals Aerodynamic performance of a hovering hawkmoth with flexible wings: a computational approach

2011 ◽  
Vol 279 (1729) ◽  
pp. 722-731 ◽  
Author(s):  
Toshiyuki Nakata ◽  
Hao Liu
Keyword(s):  
Aerodynamic Force ◽  
Dynamic Change ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Extensive Study ◽  
Flexible Wings ◽  
Wing Kinematics ◽  
Passive Deformation

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.

scholarly journals A Hybrid Reduced-Order Model for the Aeroelastic Analysis of Flexible Subsonic Wings—A Parametric Assessment

Aerospace ◽  
2018 ◽  
Vol 5 (3) ◽  
pp. 76 ◽  
Author(s):  
Marco Berci ◽  
Rauno Cavallaro
Keyword(s):  
Structural Parameters ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Reduced Order Model ◽  
Order Model ◽  
Flexible Wings ◽  
Reduced Order ◽  
Aeroelastic Analysis ◽  
Strip Theory

A hybrid reduced-order model for the aeroelastic analysis of flexible subsonic wings with arbitrary planform is presented within a generalised quasi-analytical formulation, where a slender beam is considered as the linear structural dynamics model. A modified strip theory is proposed for modelling the unsteady aerodynamics of the wing in incompressible flow, where thin aerofoil theory is corrected by a higher-fidelity model in order to account for three-dimensional effects on both distribution and deficiency of the sectional air load. Given a unit angle of attack, approximate expressions for the lift decay and build-up are then adopted within a linear framework, where the two effects are separately calculated and later combined. Finally, a modal approach is employed to write the generalised equations of motion in state-space form. Numerical results were obtained and critically discussed for the aeroelastic stability analysis of a uniform rectangular wing, with respect to the relevant aerodynamic and structural parameters. The proposed hybrid model provides sound theoretical insights and is well suited as an efficient parametric reduced-order aeroelastic tool for the preliminary multidisciplinary design and optimisation of flexible wings in the subsonic regime.

Simulation and Experiment for Rigid and Flexible Wings of Flapping-Wings Microrobots

2010 ◽  
Vol 97-101 ◽  
pp. 4513-4516
Author(s):  
Lan Liu ◽  
Zhao Xia He
Keyword(s):  
Numerical Simulation ◽  
Dynamic Performance ◽  
Unsteady Aerodynamics ◽  
Flapping Wing ◽  
Flapping Wings ◽  
Flexible Wings ◽  
Fluid Structure ◽  
Simulation And Experiment ◽  
Computational Fluid Dynamics Cfd ◽  
Coupling Deformation

In this paper, an insect-based flapping-wing flying microrobot was built which can successfully fly in the sky. The unsteady aerodynamics associated with this microrobot was studied by using the method of computational fluid dynamics (CFD). On the basis of numerical simulation, the Fluid-Structure coupling mechanics for flexible flapping-wings were studied and discussed. According to the practically developed flapping-wing microrobot, a 2-D simulation model for flexible flapping-wings was established. Fluid-Structure coupling deformation and the effects of this model on the aero dynamic performance were analyzed, which have offered a theoretical basis for design of the aircraft with flexible flapping-wing. In order to verify the results of numerical simulation, aerodynamic performance tests have been conducted for the rigid and flexible flapping-wings in a low turbulence and low Reynolds number wind tunnel.

Disturbance observer–based neural flight control for aircraft with switched time-varying distributed delays

2021 ◽  
pp. 095441002199850
Author(s):  
Dawei Wu ◽  
Jun Zhou ◽  
Hui Ye
Keyword(s):  
Flight Control ◽  
Disturbance Observer ◽  
Distributed Delay ◽  
Unsteady Aerodynamics ◽  
Feedback System ◽  
Functional Method ◽  
System Control ◽  
Time Varying ◽  
Time Varying Delay ◽  
Feedback System Control

In this article, the high angle of attack (AOA) maneuver control problem is studied under multiple disturbances and uncertainties. For the first time, the switched distributed delay is constructed to characterize the unsteady aerodynamics. Based on neural networks (NNs) and hyperbolic tangent function, the disturbance observer technique is extended to the nonstrict-feedback system control. To handle the switching problem, time-delay problem, and nonstrict-feedback problem caused by switched distributed delay terms, the Lyapunov–Krasovskii (LK) functional method and a variable separation method are cleverly combined. The proposed LK function can relax the constraints on time-varying delay. Finally, a disturbance observer–based neural finite-time prescribed performance flight control law is developed to improve the flight performance at high AOA, and its effectiveness has been verified through rigorous theoretical analysis and simulation experiments.

scholarly journals Monitoring of a Highly Flexible Aircraft Model Wing Using Time-Expanded Phase-Sensitive OTDR

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3766
Author(s):  
Miguel Soriano-Amat ◽  
David Fragas-Sánchez ◽  
Hugo F. Martins ◽  
David Vallespín-Fontcuberta ◽  
Javier Preciado-Garbayo ◽  
...  
Keyword(s):  
Optical Fibers ◽  
Fuel Efficiency ◽  
Optical Fiber Sensor ◽  
High Sensitivity ◽  
Time Domain Reflectometry ◽  
Structural Deformation ◽  
Flexible Wings ◽  
Sensing Technology ◽  
Distributed Optical Fiber Sensor ◽  
Phase Sensitive

In recent years, the use of highly flexible wings in aerial vehicles (e.g., aircraft or drones) has been attracting increasing interest, as they are lightweight, which can improve fuel-efficiency and distinct flight performances. Continuous wing monitoring can provide valuable information to prevent fatal failures and optimize aircraft control. In this paper, we demonstrate the capabilities of a distributed optical fiber sensor based on time-expanded phase-sensitive optical time-domain reflectometry (TE-ΦOTDR) technology for structural health monitoring of highly flexible wings, including static (i.e., bend and torsion), and dynamic (e.g., vibration) structural deformation. This distributed sensing technology provides a remarkable spatial resolution of 2 cm, with detection and processing bandwidths well under the MHz, arising as a novel, highly efficient monitoring methodology for this kind of structure. Conventional optical fibers were embedded in two highly flexible specimens that represented an aircraft wing, and different bending and twisting movements were detected and quantified with high sensitivity and minimal intrusiveness.

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