![Sample our Engineering & Technology journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5933/TOC-Subject-Sample-2021-Engineering-Tech.jpg"})
ABSTRACT
In the present study, an innovative concept of axial flapping wing model is analysed to study and improve the aerodynamic efficiency for vertical takeoff microaerial vehicle. The flapping kinematics are inspired by merging aquatic jellyfish locomotion, and umbrella’s in and out mechanisms with the flappers hinged around a central hub. Also, additional flappers are placed beneath the primary flappers at varied distances. The analysis is performed using FLUENT to study the effect of placing axial flappers that maximize the lift/drag ratio. The chord length of the primary flappers is fixed at 10 cm, and axial flappers at 5 cm as the model needs to be constrained according to DARPA regulations of 15cm. The flapping kinematics are chosen as inward, outward, and symmetrical based on the feasibility of flapping in the axial direction to produce the airflow for generating lift in the vertical direction. The amplitude of the flappers is set at 30° to have a comparative study of other kinematics. The flow structures developed by the interactions of vortices of flapping wings influence the aerodynamic characteristics of the model. The velocity and vorticity magnitude of the flappers are studied and analysed in detail to understand the mechanism of axial flappers in providing better lift/drag ratio. The effect of adding additional flappers underneath the primary flapper model under inwards kinematics was better than primary flapper (Model 0) which significantly increased the aerodynamic performance of axial flapper’s inter-distance variations at 5 cm by 18.3% (Model 1), at 10 cm by 15.2% (Model 2) and at 15 cm by 10.5% (Model 3). The outward and symmetric kinematics models exhibit a decrease in aerodynamic efficiency compared to inward kinematic models.
Nomenclature
| Re | = | Reynolds number |
| A | = | maximal tip displacement |
| c | = | chord length of primary flapper |
| Cl | = | lift coefficient |
| Cd | = | drag coefficient |
| Cy | = | force coefficient in y-direction |
| = | Average drag Coefficient | |
| = | Average lift coefficient | |
| s | = | Length of the axial flapper |
| a | = | inter-distance of axial flappers |
| = | unit vector perpendicular to the flow direction | |
| = | unit vector parallel to the surface of the flapping wing | |
| d | = | inter-distance between primary flappers |
| dt | = | incremental time step |
| p | = | pressure |
| u | = | velocity component in the x direction |
| v | = | velocity component in the y direction |
| θ | = | flapping amplitude in degrees |
| ρ | = | density |
| ƒ | = | frequency in Hertz |
| t | = | time step |
| = | unit vector perpendicular to the surface of the flapping wing | |
| τ | = | skin friction |
Acknowledgments
The authors wish to acknowledge the contribution of Fluid Dynamics High-Performance Computing (SIMULIA) facilities made available in the campus to carry out the present research. The software package FLUENT® 16.0 is provided by ANSYS® for research students is greatly appreciated.
Disclosure statement
No potential conflict of interest was reported by the authors.
Additional information
Notes on contributors
Vishnu Kumar G C
Dr. Vishnu Kumar G C obtained his Ph.D. from Hindustan Institute of Technology and Science, Chennai in 2018. He has extensive experience in industrial, academic and research work. His interest involves analyzing fluid-structure interaction through computational modeling. He is currently working as Assistant Professor(S.G) in School of Aeronautical Sciences, HITS, Chennai, India.
Dilip A Shah
Dr. Dilip A Shah obtained his Ph.D. from the University of Newcastle, NSW, Australia in 1988. He has been involved with experimental research in a variety of turbulent flows in both fine and large scale turbulence. After his Ph.D., he spent two years at IIT, Kanpur, India followed by nearly 25 years as a faculty in the mechanical engineering department of National University of Singapore till June 2013. Since July 2013, he has joined Hindustan Institute of Technology and science as the Head of the Aeronautical engineering department. He is currently working as Dean of The School of Aeronautical Sciences, HITS, Chennai, India.