Special Issue "Flapping Wings"

A special issue of Aerospace (ISSN 2226-4310).

Deadline for manuscript submissions: closed (30 April 2016)

Special Issue Editor

Guest Editor
Assoc. Prof. Sutthiphong Srigrarom

Aerospace Sciences Research Division, School of Engineering, University of Glasgow Singapore, Singapore Polytechnic Campus, Singapore
Website | E-Mail
Interests: Unsteady Aerodynamics, Flapping Wing MAV, Bio-Inspired Fluid Mechanics Flying/Swimming Studies, Unmanned Aerial Vehicle/Micro Aerial Vehicle (UAV), Vision-Based Navigation, Swarming of UAVs

Special Issue Information

Dear Colleagues,

Physical and aerodynamic characteristics of insects and birds in flight offer benefits over typical propeller or rotor driven miniature air vehicle (MAV) locomotion designs in certain applications. It has become the great interest of many scientists, researchers, companies and even hobbyists around the world. The purpose of this Special Issue on flapping wings is to address the current issues and developments, and help with the design challenges associated with the further advancement of the field.

Potential topics include, but are not limited to:

- Kinematics of flapping wing
- Biological aspect of flying
- Aerodynamics of flying
- Biomimetic flying machine
- Flapping wing or flying wing mechanisms
- Visual system of flying machine
- Fluid-Structure Interaction of flapping wing
- Energy and power consideration of flying machines
- Artificial Materials and Actuators
- Biological Neuromuscular system
- Flapping wing models

Dr. Sutthiphong Srigrarom
Guest Editor

Manuscript Submission Information

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Keywords

  • Flapping wing
  • Flying insects and birds
  • Flying robots
  • Biomimetics

Published Papers (6 papers)

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Research

Open AccessArticle
Comparison of Power Requirements: Flapping vs. Fixed Wing Vehicles
Received: 23 May 2016 / Revised: 31 August 2016 / Accepted: 1 September 2016 / Published: 28 September 2016
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Abstract
The power required by flapping and fixed wing vehicles in level flight is determined and compared. Based on a new modelling approach, the effects of flapping on the induced drag in flapping wing vehicles are mathematically described. It is shown that flapping causes [...] Read more.
The power required by flapping and fixed wing vehicles in level flight is determined and compared. Based on a new modelling approach, the effects of flapping on the induced drag in flapping wing vehicles are mathematically described. It is shown that flapping causes a significant increase in the induced drag when compared with a non-flapping, fixed wing vehicle. There are two effects for that induced drag increase; one is due to tilting of the lift vector caused by flapping the wings and the other results from changes in the amount of the lift vector during flapping. The induced drag increase yields a significant contribution to the power required by flapping wing vehicles. Furthermore, the power characteristics of fixed wing vehicles are dealt with. It is shown that, for this vehicle type, the propeller efficiency plays a major role. This is because there are considerable differences in the propeller efficiency when taking the size of vehicles into account. Comparing flapping and fixed wing vehicles, the conditions are shown where flapping wing vehicles have a lower power demand and where fixed wing vehicles are superior regarding the required power. There is a tendency such that fixed wing vehicles have an advantage in the case of larger size vehicles and flapping wing vehicles have an advantage in the case of smaller size ones. Full article
(This article belongs to the Special Issue Flapping Wings)
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Graphical abstract

Open AccessArticle
Comparison of the Average Lift Coefficient ͞CL and Normalized Lift ͞ηL for Evaluating Hovering and Forward Flapping Flight
Received: 3 June 2016 / Revised: 19 July 2016 / Accepted: 19 July 2016 / Published: 29 July 2016
Cited by 2 | PDF Full-text (1145 KB) | HTML Full-text | XML Full-text
Abstract
The capability of flapping wings to generate lift is currently evaluated by using the lift coefficient C¯L, a dimensionless number that is derived from the basal equation that calculates the steady-state lift coefficient CL for fixed wings. In contrast [...] Read more.
The capability of flapping wings to generate lift is currently evaluated by using the lift coefficient C ¯ L , a dimensionless number that is derived from the basal equation that calculates the steady-state lift coefficient CL for fixed wings. In contrast to its simple and direct application to fixed wings, the equation for C ¯ L requires prior knowledge of the flow field along the wing span, which results in two integrations: along the wing span and over time. This paper proposes an alternate average normalized lift η ¯ L that is easy to apply to hovering and forward flapping flight, does not require prior knowledge of the flow field, does not resort to calculus for its solution, and its lineage is close to the basal equation for steady state CL. Furthermore, the average normalized lift η ¯ L converges to the legacy CL as the flapping frequency is reduced to zero (gliding flight). Its ease of use is illustrated by applying the average normalized lift η ¯ L to the hovering and translating flapping flight of bumblebees. This application of the normalized lift is compared to the same application using two widely-accepted legacy average lift coefficients: the first C ¯ L as defined by Dudley and Ellington, and the second lift coefficient by Weis-Fogh. Furthermore, it is shown that the average normalized lift η ¯ L has a physical meaning: that of the ratio of work exerted by the flapping wings onto the surrounding flow field and the kinetic energy available at the aerodynamic surfaces during the generation of lift. The working equation for the average normalized lift η ¯ L is derived and is presented as a function of Strouhal number, St. Full article
(This article belongs to the Special Issue Flapping Wings)
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Graphical abstract

Open AccessArticle
Analysis of Kinematics of Flapping Wing UAV Using OptiTrack Systems
Received: 9 May 2016 / Revised: 13 July 2016 / Accepted: 13 July 2016 / Published: 26 July 2016
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Abstract
An analysis of the kinematics of a flapping membrane wing using experimental kinematic data is presented. This motion capture technique tracks the positon of the retroreflective marker(s) placed on the left wing of a 1.3-m-wingspan ornithopter. The time-varying three-dimensional data of the wing [...] Read more.
An analysis of the kinematics of a flapping membrane wing using experimental kinematic data is presented. This motion capture technique tracks the positon of the retroreflective marker(s) placed on the left wing of a 1.3-m-wingspan ornithopter. The time-varying three-dimensional data of the wing kinematics were recorded for a single frequency. The wing shape data was then plotted on a two-dimensional plane to understand the wing dynamic behaviour of an ornithopter. Specifically, the wing tip path, leading edge bending, wing membrane shape, local twist, stroke angle and wing velocity were analyzed. As the three characteristic angles can be expressed in the Fourier series as a function of time, the kinematics of the wing can be computationally generated for the aerodynamic study of flapping flight through the Fourier coefficients presented. Analysis of the ornithopter wing showed how the ornithopter closely mimics the flight motions of birds despite several physical limitations. Full article
(This article belongs to the Special Issue Flapping Wings)
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Graphical abstract

Open AccessArticle
Hydrodynamic Performance of Aquatic Flapping: Efficiency of Underwater Flight in the Manta
Received: 7 April 2016 / Revised: 28 June 2016 / Accepted: 1 July 2016 / Published: 11 July 2016
Cited by 24 | PDF Full-text (10429 KB) | HTML Full-text | XML Full-text
Abstract
The manta is the largest marine organism to swim by dorsoventral oscillation (flapping) of the pectoral fins. The manta has been considered to swim with a high efficiency stroke, but this assertion has not been previously examined. The oscillatory swimming strokes of the [...] Read more.
The manta is the largest marine organism to swim by dorsoventral oscillation (flapping) of the pectoral fins. The manta has been considered to swim with a high efficiency stroke, but this assertion has not been previously examined. The oscillatory swimming strokes of the manta were examined by detailing the kinematics of the pectoral fin movements swimming over a range of speeds and by analyzing simulations based on computational fluid dynamic potential flow and viscous models. These analyses showed that the fin movements are asymmetrical up- and downstrokes with both spanwise and chordwise waves interposed into the flapping motions. These motions produce complex three-dimensional flow patterns. The net thrust for propulsion was produced from the distal half of the fins. The vortex flow pattern and high propulsive efficiency of 89% were associated with Strouhal numbers within the optimal range (0.2–0.4) for rays swimming at routine and high speeds. Analysis of the swimming pattern of the manta provided a baseline for creation of a bio-inspired underwater vehicle, MantaBot. Full article
(This article belongs to the Special Issue Flapping Wings)
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Graphical abstract

Open AccessArticle
The Efficiency of a Hybrid Flapping Wing Structure—A Theoretical Model Experimentally Verified
Received: 7 April 2016 / Revised: 22 June 2016 / Accepted: 30 June 2016 / Published: 5 July 2016
Cited by 1 | PDF Full-text (19338 KB) | HTML Full-text | XML Full-text
Abstract
To propel a lightweight structure, a hybrid wing structure was designed; the wing’s geometry resembled a rotor blade, and its flexibility resembled an insect’s flapping wing. The wing was designed to be flexible in twist and spanwise rigid, thus maintaining the aeroelastic advantages [...] Read more.
To propel a lightweight structure, a hybrid wing structure was designed; the wing’s geometry resembled a rotor blade, and its flexibility resembled an insect’s flapping wing. The wing was designed to be flexible in twist and spanwise rigid, thus maintaining the aeroelastic advantages of a flexible wing. The use of a relatively “thick” airfoil enabled the achievement of higher strength to weight ratio by increasing the wing’s moment of inertia. The optimal design was based on a simplified quasi-steady inviscid mathematical model that approximately resembles the aerodynamic and inertial behavior of the flapping wing. A flapping mechanism that imitates the insects’ flapping pattern was designed and manufactured, and a set of experiments for various parameters was performed. The simplified analytical model was updated according to the tests results, compensating for the viscid increase of drag and decrease of lift, that were neglected in the simplified calculations. The propelling efficiency of the hovering wing at various design parameters was calculated using the updated model. It was further validated by testing a smaller wing flapping at a higher frequency. Good and consistent test results were obtained in line with the updated model, yielding a simple, yet accurate tool, for flapping wings design. Full article
(This article belongs to the Special Issue Flapping Wings)
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Graphical abstract

Open AccessArticle
The Effect of the Phase Angle between the Forewing and Hindwing on the Aerodynamic Performance of a Dragonfly-Type Ornithopter
Received: 4 November 2015 / Revised: 28 December 2015 / Accepted: 19 January 2016 / Published: 25 January 2016
Cited by 3 | PDF Full-text (10575 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Dragonflies achieve agile maneuverability by flapping four wings independently. Different phase angles between the flapping forewing and hindwing have been observed during various flight modes. The aerodynamic performance depends on phase angle control, as exemplified by an artificial flying ornithopter. Here, we present [...] Read more.
Dragonflies achieve agile maneuverability by flapping four wings independently. Different phase angles between the flapping forewing and hindwing have been observed during various flight modes. The aerodynamic performance depends on phase angle control, as exemplified by an artificial flying ornithopter. Here, we present a dragonfly-like ornithopter whose phase angle was designed to vary according to the phase lag between the slider-cranks of the forewing and hindwing. Two microelectromechanical systems (MEMS) differential pressure sensors were attached to the center of both forewing and hindwing to evaluate the aerodynamic performance during flapping motions when the phase angle was changed. By varying the phase angle in both the tethered condition and free-flight, the performance of the forewing remained approximately constant, whereas that of the hindwing exhibited obvious variations; the maximum average value was two-fold higher than the minimum. The experimental results suggest that simple phase angle changes enable a flying ornithopter to control flight force balance without complex changes in the wing kinematics. Full article
(This article belongs to the Special Issue Flapping Wings)
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