Effects of Stroke Deviation on Aerodynamic Force Production of a Flapping Wing

AIAA Journal ◽  
2018 ◽  
Vol 56 (1) ◽  
pp. 25-35 ◽  
Author(s):  
Guoyu Luo ◽  
Gang Du ◽  
Mao Sun
Keyword(s):  
Aerodynamic Force ◽  
Force Production ◽  
Flapping Wing

Deformable Blade Element and Unsteady Vortex Lattice Fluid-Structure Interaction Modeling of a 2D Flapping Wing

2020 ◽  
Author(s):  
Joseph Reade ◽  
Mark A. Jankauski
Keyword(s):  
Vortex Lattice ◽  
Normal Force ◽  
Aerodynamic Force ◽  
Fluid Structure Interaction ◽  
Force Production ◽  
Flapping Wing ◽  
Energetic Efficiency ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Blade Element

Abstract Flapping insect wings experience appreciable deformation due to aerodynamic and inertial forces. This deformation is believed to benefit the insect’s aerodynamic force production as well as energetic efficiency. However, the fluid-structure interaction (FSI) models used to estimate wing deformations are often computationally demanding and are therefore challenged by parametric studies. Here, we develop a simple FSI model of a flapping wing idealized as a two-dimensional pitching-plunging airfoil. Using the Lagrangian formulation, we derive the reduced-order structural framework governing wing’s elastic deformation. We consider two fluid models: quasi-steady Deformable Blade Element Theory (DBET) and Unsteady Vortex Lattice Method (UVLM). DBET is computationally economical but does not provide insight into the flow structure surrounding the wing, whereas UVLM approximates flows but requires more time to solve. For simple flapping kinematics, DBET and UVLM produce similar estimates of the aerodynamic force normal to the surface of a rigid wing. More importantly, when the wing is permitted to deform, DBET and UVLM agree well in predicting wingtip deflection and aerodynamic normal force. The most notable difference between the model predictions is a roughly 20° phase difference in normal force. DBET estimates wing deformation and force production approximately 15 times faster than UVLM for the parameters considered, and both models solve in under a minute when considering 15 flapping periods. Moving forward, we will benchmark both low-order models with respect to high fidelity computational fluid dynamics coupled to finite element analysis, and assess the agreement between DBET and UVLM over a broader range of flapping kinematics.

scholarly journals Towards Bio-Inspiration, Development, and Manufacturing of a Flapping-Wing Micro Air Vehicle

Drones ◽  
2020 ◽  
Vol 4 (3) ◽  
pp. 39
Author(s):  
P. Lane ◽  
G. Throneberry ◽  
I. Fernandez ◽  
M. Hassanalian ◽  
R. Vasconcellos ◽  
...  
Keyword(s):  
Aerodynamic Force ◽  
Force Production ◽  
Flight Test ◽  
Flapping Wing ◽  
Micro Air Vehicle ◽  
Air Vehicle ◽  
Successful Design ◽  
The Stability ◽  
And Control ◽  
The Impact

Throughout the last decade, there has been an increased demand for intricate flapping-wing drones with different capabilities than larger drones. The design of flapping-wing drones is focused on endurance and stability, as these are two of the main challenges of these systems. Researchers have recently been turning towards bioinspiration as a way to enhance aerodynamic performance. In this work, the propulsion system of a flapping-wing micro air vehicle is investigated to identify the limitations and drawbacks of specific designs. Each system has a tandem wing configuration inspired by a dragonfly, with wing shapes inspired by a bumblebee. For the design of this flapping-wing, a sizing process is carried out. A number of actuation mechanisms are considered, and two different mechanisms are designed and integrated into a flapping-wing system and compared to one another. The second system is tested using a thrust stand to investigate the impact of wing configurations on aerodynamic force production and the trend of force production from varying flapping frequency. Results present the optimal wing configuration of those tested and that an angle of attack of two degrees yields the greatest force production. A tethered flight test is conducted to examine the stability and aerodynamic capabilities of the drone, and challenges of flapping-wing systems and solutions that can lead to successful flight are presented. Key challenges to the successful design of these systems are weight management, force production, and stability and control.

scholarly journals Characterizing and modeling the enhancement of lift and payload capacity resulting from thrust augmentation in a propeller-assisted flapping wing air vehicle

2017 ◽  
Vol 10 (1) ◽  
pp. 50-69 ◽  
Author(s):  
Alex E Holness ◽  
Hugh A Bruck ◽  
Satyandra K Gupta
Keyword(s):  
Mixed Mode ◽  
Aerodynamic Force ◽  
Force Production ◽  
Flight Time ◽  
Flapping Wing ◽  
Operating Conditions ◽  
Biologically Inspired ◽  
Air Vehicle ◽  
Payload Capacity ◽  
Aerodynamic Lift

Biologically-inspired flapping wing flight is attractive at low Reynolds numbers and at high angles of attack, where fixed wing flight performance declines precipitously. While the merits of flapping propulsion have been intensely investigated, enhancing flapping propulsion has proven challenging because of hardware constraints and the complexity of the design space. For example, increasing the size of wings generates aerodynamic forces that exceed the limits of actuators used to drive the wings, reducing flapping amplitude at higher frequencies and causing thrust to taper off. Therefore, augmentation of aerodynamic force production from alternative propulsion modes can potentially enhance biologically-inspired flight. In this paper, we explore the use of auxiliary propellers on Robo Raven, an existing flapping wing air vehicle (FWAV), to augment thrust without altering wing design or flapping mechanics. Designing such a platform poses two major challenges. First, potential for negative interaction between the flapping and propeller airflow reducing thrust generation. Second, adding propellers to an existing platform increases platform weight and requires additional power from heavier energy sources for comparable flight time. In this paper, three major findings are reported addressing these challenges. First, locating the propellers behind the flapping wings (i.e. in the wake) exhibits minimal coupling without positional sensitivity for the propeller placement at or below the platform centerline. Second, the additional thrust generated by the platform does increase aerodynamic lift. Third, the increase in aerodynamic lift offsets the higher weight of the platform, significantly improving payload capacity. The effect of varying operational payload and flight time for different mixed mode operating conditions was predicted, and the trade-off between the operational payload and operating conditions for mixed mode propulsion was characterized. Flight tests revealed the improved agility of the platform when used with static placement of the wings for various aerobatic maneuvers, such as gliding, diving, or loops.

The Effects of Wakes on Aerodynamic Characteristics of Flapping Wings in Clap-and-Fling Motion at Re of ~104

2018 ◽  
Author(s):  
Jong-Seob Han ◽  
Jae-Hung Han
Keyword(s):  
Aerodynamic Force ◽  
Force Production ◽  
Micro Air Vehicles ◽  
Aerodynamic Characteristics ◽  
Flapping Wing ◽  
Flapping Wings ◽  
Water Tank ◽  
Cross Sectional ◽  
Robotic Arms ◽  
Tip Vortices

In this paper, aerodynamic characteristics of two flapping wings in clap-and-fling motion at Re of ∼104, which corresponds to the flight regime of flapping-wing micro air vehicles, was investigated. The test employing dynamically scaled-up robotic arms installed on a water tank revealed that the wingbeat motion at such high Re in1duced the fully developed wake within two wingbeat cycles. This wake widely influenced the lift production covering the entire wingbeat period; the wings earned the additional lift during the entire downstroke, and lost the lift during the upstroke. Chordwise cross-sectional DPIV showed the massive downwash with enlarged tip vortices, when the wake was fully developed. The wake blew down the headwind and reduced the effective angles of attack. In the case of the clap-and-fling motion, the wake was leaned toward the dorsal part, in which the wings created the clap-and-fling motion, causing the global fluctuation of the aerodynamic force production.

Wing-Wake Interaction of Insect-Like Flapping Wing in Hover: Effect of Aspect Ratio and Kinematics at Re~104

2019 ◽  
Author(s):  
Reynolds Addo-Akoto ◽  
Jong-Seob Han ◽  
Jae-Hung Han
Keyword(s):  
Aspect Ratio ◽  
Time Course ◽  
Aerodynamic Force ◽  
Flapping Wing ◽  
Windward Side ◽  
Water Tank ◽  
Image Velocimetry ◽  
Wake Interaction ◽  
Entire Flow ◽  
Accelerated Flow

Abstract In this paper, the effect of wing aspect ratio and kinematics on wing-wake interaction at Re∼104, which matched the flight regime of flapping-wing micro air vehicle (FWMAV), was investigated. The dynamically scaled-up robotic model submerged in a water tank environment revealed that the wing-wake interaction augmented lift across a decrease in both aspect ratio and wing pitching duration. At such high Re, a time-course digital particle image velocimetry (DPIV) measurement showed the entire flow was strongly dominated by trailing-edge vortices (TEV). A pair of counter-rotating TEV was found to induce a jetlike flow towards the windward side of the wing at stroke reversal. The transfer of momentum from the accelerated flow to the wing caused the enhanced lift. The size of the pair vortex decreased for an increase in both aspect ratio and wing pitching duration. The size of the TEV pair was the key feature found to generate the observed aerodynamic force characteristics.

scholarly journals Scaling of the performance of insect-inspired passive-pitching flapping wings

2019 ◽  
Vol 16 (161) ◽  
pp. 20190609 ◽  
Author(s):  
Kit Sum Wu ◽  
Jerome Nowak ◽  
Kenneth S. Breuer
Keyword(s):  
Scaling Laws ◽  
Aerodynamic Force ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Flapping Wing ◽  
Dimensionless Parameters ◽  
Linear Elastic ◽  
Simple Implementation ◽  
Pitch Regulation ◽  
Cauchy Number

Flapping flight using passive pitch regulation is a commonly used mode of thrust and lift generation in insects and has been widely emulated in flying vehicles because it allows for simple implementation of the complex kinematics associated with flapping wing systems. Although robotic flight employing passive pitching to regulate angle of attack has been previously demonstrated, there does not exist a comprehensive understanding of the effectiveness of this mode of aerodynamic force generation, nor a method to accurately predict its performance over a range of relevant scales. Here, we present such scaling laws, incorporating aerodynamic, inertial and structural elements of the flapping-wing system, validating the theoretical considerations using a mechanical model which is tested for a linear elastic hinge and near-sinusoidal stroke kinematics over a range of scales, hinge stiffnesses and flapping frequencies. We find that suitably defined dimensionless parameters, including the Reynolds number, Re , the Cauchy number, Ch , and a newly defined ‘inertial-elastic’ number, IE, can reliably predict the kinematic and aerodynamic performance of the system. Our results also reveal a consistent dependency of pitching kinematics on these dimensionless parameters, providing a connection between lift coefficient and kinematic features such as angle of attack and wing rotation.

scholarly journals Dipteran wing motor-inspired flapping flight versatility and effectiveness enhancement

2015 ◽  
Vol 12 (104) ◽  
pp. 20141367 ◽  
Author(s):  
R. L. Harne ◽  
K. W. Wang
Keyword(s):  
Structural Model ◽  
Aerodynamic Force ◽  
Flapping Wing ◽  
Flapping Flight ◽  
Axial Stiffness ◽  
Small Scale ◽  
Aerodynamic Efficiency ◽  
Linear Motors ◽  
Air Vehicle ◽  
Compression Characteristics

Insects are a prime source of inspiration towards the development of small-scale, engineered, flapping wing flight systems. To help interpret the possible energy transformation strategies observed in Diptera as inspiration for mechanical flapping flight systems, we revisit the perspective of the dipteran wing motor as a bistable click mechanism and take a new, and more flexible, outlook to the architectural composition previously considered. Using a representative structural model alongside biological insights and cues from nonlinear dynamics, our analyses and experimental results reveal that a flight mechanism able to adjust motor axial support stiffness and compression characteristics may dramatically modulate the amplitude range and type of wing stroke dynamics achievable. This corresponds to significantly more versatile aerodynamic force generation without otherwise changing flapping frequency or driving force amplitude. Whether monostable or bistable, the axial stiffness is key to enhance compressed motor load bearing ability and aerodynamic efficiency, particularly compared with uncompressed linear motors. These findings provide new foundation to guide future development of bioinspired, flapping wing mechanisms for micro air vehicle applications, and may be used to provide insight to the dipteran muscle-to-wing interface.

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