Research On The Lift Coefficient For The Flapping Motion Of A Wing Based On FLUENT

The research and fabrication of insect-like flapping-wing micro air vechicle (MAV) have recently received much attentions in the field of mechanical engineering. One of important issues concerned with that is the study of aerodynamic characteristics when the wing is flapping in air, and the question how to get more effective lift and larger lift coefficient is crucial for the design of MAV. Based on some results obtained by other researchers, the aerodynamic characteristic of flapping motion is analyzed by employing the computational fluid dynamics software, namely Fluent, in this thesis.The emphasis of this thesis is placed on how the lift coefficient is affected by the variations of style and parameter of the flapping motion, and especially chaotic motion.The results shows that the flapping motion by taking a crank-rocker mechanism as the flapping wing mechanism will result in a larger lift coefficient than the flapping motions which are with harmonic or constant angular velocity. The mean lift coefficient increases with the increasing of frequency or/and the amplitude of flapping motion. However, the influence of frequency and the amplitude on the mean lift coefficient will be reduced if the frequency or the amplitude is larger than a certain value.The Weis-Fogh mechanism is a main mechanism of lift generation in the flight of an insect, and is an important consideration in the design of MAV. The results here indicate that Weis-Fogh mechanism can produce much larger lift coefficient, and the higher the opening angular velocity, the larger the lift coefficient, and so do the opening amplitude. But when the opening amplitude is larger than the value about 60°, the lift coefficient will decrease abruptly.It has been found by other researchers that the motion of flapping wing will become chaotic under certain circumstances. In this thesis, the flapping motion is perturbed with a simple chaotic motion, and the lift coefficient produced by such flapping motion is studied. The result shows that the chaotic motion of the wing will make the lift coefficient decrease, and the more intense the chaotic motion, the more obviously the lift coefficient decrease.