scholarly journals Effects of spanwise flexibility on the performance of flapping flyers in forward flight

2017 ◽  
Vol 14 (136) ◽  
pp. 20170725 ◽  
Author(s):  
Deepa Kodali ◽  
Cory Medina ◽  
Chang-kwon Kang ◽  
Hikaru Aono
Keyword(s):  
Aerodynamic Force ◽  
Dynamic Balance ◽  
Transverse Displacement ◽  
Flexible Wings ◽  
Restoring Force ◽  
Flexible Wing ◽  
Induced Drag ◽  
Aspect Ratios ◽  
Aeroelastic Model ◽  
Spanwise Flexibility

Flying animals possess flexible wings that deform during flight. The chordwise flexibility alters the wing shape, affecting the effective angle of attack and hence the surrounding aerodynamics. However, the effects of spanwise flexibility on the locomotion are inadequately understood. Here, we present a two-way coupled aeroelastic model of a plunging spanwise flexible wing. The aerodynamics is modelled with a two-dimensional, unsteady, incompressible potential flow model, evaluated at each spanwise location of the wing. The two-way coupling is realized by considering the transverse displacement as the effective plunge under the dynamic balance of wing inertia, elastic restoring force and aerodynamic force. The thrust is a result of the competition between the enhancement due to wing deformation and induced drag. The results for a purely plunging spanwise flexible wing agree well with experimental and high-fidelity numerical results from the literature. Our analysis suggests that the wing aspect ratio of the abstracted passerine and goose models corresponds to the optimal aeroelastic response, generating the highest thrust while minimizing the power required to flap the wings. At these optimal aspect ratios, the flapping frequency is near the first spanwise natural frequency of the wing, suggesting that these birds may benefit from the resonance to generate thrust.

scholarly journals Preliminary investigation of use of flexible folding wing tips for static and dynamic load alleviation

2016 ◽  
Vol 121 (1235) ◽  
pp. 73-94 ◽  
Author(s):  
A. Castrichini ◽  
V. Hodigere Siddaramaiah ◽  
D.E. Calderon ◽  
J.E. Cooper ◽  
T. Wilson ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
Preliminary Investigation ◽  
Aircraft Design ◽  
Dynamic Loads ◽  
Induced Drag ◽  
Aeroelastic Model ◽  
Static And Dynamic Loads ◽  
Folding Wing ◽  
Wing Tips ◽  
Wing Tip

ABSTRACTA recent consideration in aircraft design is the use of folding wing-tips with the aim of enabling higher aspect ratio aircraft with less induced drag while also meeting airport gate limitations. This study investigates the effect of exploiting folding wing-tips in flight as a device to reduce both static and dynamic loads. A representative civil jet aircraft aeroelastic model was used to explore the effect of introducing a wing-tip device, connected to the wings with an elastic hinge, on the load behaviour. For the dynamic cases, vertical discrete gusts and continuous turbulence were considered. The effects of hinge orientation, stiffness, damping and wing-tip weight on the static and dynamic response were investigated. It was found that significant reductions in both the static and dynamic loads were possible. For the case considered, a 25% increase in span using folding wing-tips resulted in almost no increase in loads.

scholarly journals Piezoelectric Wind Energy Harvesting from Self-Excited Vibration of Square Cylinder

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Junlei Wang ◽  
Sheng Wen ◽  
Xingqiang Zhao ◽  
Min Zhang ◽  
Jingyu Ran
Keyword(s):  
Wind Energy ◽  
Aerodynamic Force ◽  
Load Resistance ◽  
Open Circuit ◽  
Transverse Displacement ◽  
Square Cylinder ◽  
Force Output ◽  
Vortex Induced Vibration ◽  
Wind Speeds ◽  
Excited Vibration

Self-excited vibration of a square cylinder has been considered as an effective way in harvesting piezoelectric wind energy. In present work, both of the vortex-induced vibration and unstable galloping phenomenon process are investigated in a reduced velocity (Ur=U/ωn·D) range of4≤Ur≤20with load resistance ranging in100 Ω≤R≤1 MΩ. The vortex-induced vibration covers presynchronization, synchronization, and postsynchronization branches. An aeroelectromechanical model is given to describe the coupling of the dynamic equation of the fluid-structure interaction and the equation of Gauss law. The effects of load resistance are investigated in both the open-circuit and close-circuit system by a linear analysis, which covers the parameters of the transverse displacement, aerodynamic force, output voltage, and harvested power utilized to measure the efficiency of the system. The highest level of the transverse displacement and the maximum value of harvested power of synchronization branch during the vortex-induced vibration and galloping are obtained. The results show that the large-amplitude galloping at high wind speeds can generate energy. Additionally, energy can be harvested by utilization of the lock-in phenomenon of vortex-induced vibration under low wind speed.

Numerical Simulation of Micro Air Vehicles With Membrane Wings

2007 ◽  
Author(s):  
Xiaoqin Zhang ◽  
Ling Tian
Keyword(s):  
Numerical Simulation ◽  
Pressure Distribution ◽  
Micro Air Vehicles ◽  
Flexible Wings ◽  
Design Modification ◽  
Structure Deformation ◽  
Flexible Wing ◽  
Fluid Field ◽  
Distributed Pressure ◽  
Air Vehicles

Micro Air Vehicles (MAVs) have advantages of small size, low cost, flexibility and controllability etc., so they will be applied widely in military and civilian fields. They have obviously low Reynolds number aerodynamics, which is different from traditional aircrafts. In this paper, numerical simulation based on fluid-structure interaction for flexible wing MAVs is presented. Flexible wings are composed of carbon frames and covered with membrane skins. Because flexible wing MAVs easily deform in airflow, both structure model and fluid model should be built. The two models are connected by interfaces of membrane wings, which transmit distributed pressure and deformations of membrane wings. When membrane wings are located in airflow, they will deform with actions of surrounding airflow. Deformation of membrane wings also affects airflow and pressure distributed on the wings’ surfaces will also be changed relatively, which will compel the shape of membrane wings to be changed once more. Therefore, numerical simulation of flexible wing MAVs is not only the analysis of fluid field, but also the structure deformation effects. Navier-Stokes Equations are nonlinear and complicated, so direct interaction of fluid and structure equations is rather difficult and costs too much time. Indirect interaction method is more feasible and it is adopted in this paper. Structure deformation and distributed pressure on membrane wings surfaces are calculated separately, and then pressure distribution from fluid solver is transmitted to structure solver. After structure deformation is calculated in structure solver, it will be transmitted to fluid field again. Iteration goes on in this way and finally converges. Simulation results show the deformation, stress and pressure distribution of flexible wings. All these results are good reference for MAVs design, modification and wind tunnel experiments generally.

Optimal Scheduling of Control Surfaces Flexible Wings to Reduce Induced Drag

2006 ◽  
Vol 43 (6) ◽  
pp. 1655-1661 ◽  
Author(s):  
Raymond M. Kolonay ◽  
Franklin E. Eastep
Keyword(s):  
Optimal Scheduling ◽  
Flexible Wings ◽  
Induced Drag ◽  
Control Surfaces

scholarly journals Effect of tip vortices on membrane vibration of flexible wings with different aspect ratios

2016 ◽  
Vol 114 ◽  
pp. 02028 ◽  
Author(s):  
Mustafa Serdar Genç ◽  
Halil Hakan Açikel ◽  
Hacımurat Demir ◽  
Mustafa Özden ◽  
Mücahit Çağdaş ◽  
...  
Keyword(s):  
Flexible Wings ◽  
Tip Vortices ◽  
Aspect Ratios ◽  
Membrane Vibration

scholarly journals Modeling of Gust Energy Extractions through Aeroelastic Tailoring

2021 ◽  
Author(s):  
Michael Melville
Keyword(s):  
Interaction Model ◽  
Computational Time ◽  
Energy Extraction ◽  
Flexible Wings ◽  
Aeroelastic Tailoring ◽  
Aeroelastic Model ◽  
Tightly Coupled ◽  
Explicit Finite Difference ◽  
Energy Gains ◽  
Explicit Finite Difference Method

A tightly coupled fluid-structure interaction model is presented for studying the performance of flexible wings that encounter atmospheric gusts. The aerodynamic module uses a higher-order potential flow method, that provides numerical robustness and efficiency. The structural dynamics is modelled through an explicit finite difference method of the time-depenedent Euler-Bernoulli equations. Coupled together, these approaches offer numerical accuracy at a fraction of the computational time than is required for higher fidelity approaches. Previous research has suggested energy gains are possible from atmospheric gusts through aeroelastic tailoring. Case studies were performed using the aeroelastic model to investigate the merit of using aeroelastic tailoring as a passive means for performance improvement. Design trends were established that highlight configurations that achieve the best energy extraction from a gust. Reductions in wing drag of between 6.9% and 10.5% were observed, while gains of 0.25% between different aeroelastic configurations were presented. The forward sweeping of the elastic axis was deemed to have the greatest effect on energy extraction capabilities.

Flexibility of Flapping Rotor Wing and its Effect on Aerodynamic Characteristic

2012 ◽  
Vol 184-185 ◽  
pp. 239-243
Author(s):  
Jing Lu ◽  
Ning Jun Fan ◽  
Yi Wei Wang
Keyword(s):  
Aerodynamic Characteristic ◽  
Aerodynamic Force ◽  
Flapping Wing ◽  
Variable Speed ◽  
New Model ◽  
Flexible Wing ◽  
Wing Model ◽  
Speed Factor ◽  
Rotor Wing ◽  
Rigid Model

In the previous study, the rigid model of flapping wing rotor ignores the flexible factors to describe its in detail. So a new flexible wing model is established here to further study the aerodynamic characteristic of this wing. And a variable-speed factor is taken into account in this new model too. It is found that the deformation position and amplitude are both useful to increase aerodynamic force. The variable-speed factor has a significant effect on aerodynamic characteristic. In the end, the results show the flexible wing has much better performance than rigid one.

scholarly journals The experimental study of aerodynamic characteristics with wing flexibility for hawkmoth-like wings in hovering flight

2021 ◽  
Author(s):  
YeongGyun Ryu
Keyword(s):  
Experimental Study ◽  
High Speed ◽  
Aerodynamic Force ◽  
Aerodynamic Characteristics ◽  
Flow Structures ◽  
Water Tank ◽  
Hovering Flight ◽  
Flexible Wings ◽  
Image Velocimetry ◽  
Rigid Wing

An experimental study on flapping wing flexibility in hovering flight has been conducted to investigate the wing flexibility for insect-inspired flapping Micro Aerial Vehicles (MAVs). Hawkmoth-like wing models, derived from Manduca sexta, were made of Polycarbonate (PC) sheet with a spanwise length of 200 mm and an aspect ratio of 6.18. For the distributions of wing flexibility, the wing thickness was selected as the design variable: rigid wing (3 mm-thick) and flexible wings (2, 1, 0.8, 0.5, 0.35, 0.2, and 0.1 mm-thick). In the experiment, the wing models were constrained to the symmetrical and sinusoidal flapping motions with sweeping and rotating amplitudes of 120° and 90° in water tank with size of 3.5 m×1.0 m×1.1 m. Aerodynamic force and flow structures for flapping the wing were measured using a six-axis force/torque sensor and a high speed camera with a laser using Digital Particle Image Velocimetry (DPIV). To compare the flow structures of flexible wings with rigid wing, they were captured at the same chordwise cross-section as the rigid wing, 50% of wing length. Based on the experimental results, vortices and aerodynamic force. Consequently, the wing with thickness of 0.8 mm has better aerodynamic characteristics than other wings in hovering flight. This finding will be instrumental in identifying the range of wing flexibilities that improves the aerodynamic efficiency for the development of insect-inspired flapping MAVs.

scholarly journals Bifurcation Analysis with Aerodynamic-Structure Uncertainties by the Nonintrusive PCE Method

2017 ◽  
Vol 2017 ◽  
pp. 1-17
Author(s):  
Linpeng Wang ◽  
Yuting Dai ◽  
Chao Yang
Keyword(s):  
Polynomial Chaos ◽  
Aerodynamic Force ◽  
Polynomial Chaos Expansion ◽  
Limit Cycle Oscillation ◽  
Structure Parameters ◽  
Chaos Expansion ◽  
Aeroelastic Model ◽  
Aerodynamic Parameters ◽  
Cycle Oscillation ◽  
The Time Domain

An aeroelastic model for airfoil with a third-order stiffness in both pitch and plunge degree of freedom (DOF) and the modified Leishman–Beddoes (LB) model were built and validated. The nonintrusive polynomial chaos expansion (PCE) based on tensor product is applied to quantify the uncertainty of aerodynamic and structure parameters on the aerodynamic force and aeroelastic behavior. The uncertain limit cycle oscillation (LCO) and bifurcation are simulated in the time domain with the stochastic PCE method. Bifurcation diagrams with uncertainties were quantified. The Monte Carlo simulation (MCS) is also applied for comparison. From the current work, it can be concluded that the nonintrusive polynomial chaos expansion can give an acceptable accuracy and have a much higher calculation efficiency than MCS. For aerodynamic model, uncertainties of aerodynamic parameters affect the aerodynamic force significantly at the stage from separation to stall at upstroke and at the stage from stall to reattach at return. For aeroelastic model, both uncertainties of aerodynamic parameters and structure parameters impact bifurcation position. Structure uncertainty of parameters is more sensitive for bifurcation. When the nonlinear stall flutter and bifurcation are concerned, more attention should be paid to the separation process of aerodynamics and parameters about pitch DOF in structure.

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