Analyses and simulations of propulsion mechanisms for flapping wings with the extension of Undulate Propulsion Theory

This paper puts forward a new method to address the propulsion mechanism of flapping wing aircrafts, or ornithopter. This new method is the extension of Undulate Propulsion Theory. After reviewing several famous theories of flapping wings, we believe that the method integrating undulate propulsion theory with actuator disk theory can describe the propulsion mechanism of flapping wings more vividly. Then a propulsion expression for flapping wings is derived, which focuses on how airflow velocity, plunging frequency and twisting angle affect the propulsion. Simulations demonstrate that the expression is reasonable and able to provide scientific guidance for the design of flapping wings.