Micro air vehicles : flapping wing propulsion

• Main Author: Tan, Rui Xia.
• Other Authors: Jorg Uwe Schluter
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Aeronautical engineering::Aircraft
• Online Access: http://hdl.handle.net/10356/40633
• Institution: Nanyang Technological University

The potential of flapping wing aerodynamics for application to micro-air vehicles has led to recent interest in the area of flapping wing propulsion especially in the low Reynolds flight regime. In this FYP report, the author investigated a two-dimensional computational model of a pure plunging flat plate and its corresponding force coefficients and vortex flows. The focus of this project is to analyse the relationship between drag coefficient and plunging frequency of a flat plate in Reynolds flow of 104. Firstly, the test case of a stationary cylinder in the same Reynolds number regime is set up. Velocity measurements at various wake distances (4d-7d behind centre of cylinder) were obtained (i) experimentally using hot wire anemometer in a water tunnel and (ii) computationally using Jetcode, based on the immersed boundary method. Drag coefficient is found to increase with increasing wake distance. The experimental and computational drag coefficients obtained were also compared with values found in literature and all were in good agreement, within 10% of each other. Secondly, the flat plate was set to plunge at 8 non-dimensionalised frequencies ranging from 0.129 to 0.275 at constant non-dimensionalised amplitude of 0.34. The results show a general increasing trend of thrust force produced by the flat plate with increasing plunging frequencies. Thrust is observed to be produced when the kh value exceeds 0.05 and even appears to exceed a plunging NACA0012 airfoil in Reynolds flow of 105 at 0.275 at kh=0.54. Flow visualisation of the direction of vortices at frequency 0.129 and 0.275 indicated drag and thrust respectively. Drag coefficients were found to be relatively constant at different wake distances. Lastly, additional simulations with finer grid and hot wire measurements of wake velocities of the plunging flat plate would help to shed more light into the difference in values of force coefficients computed from pressure forces acting directly on the cylinder and B.M. Jones‟ wake transverse method.