Air flow over a flapping bird’s wing at low Reynolds numbers: discussions in a teaching demonstration

Abstract

Abstract Bird wings are frequently modelled in the aerodynamics literature under the assumption that they are static aerofoils. Air flows over real bird wings can violate this assumption, both because of the topology of the wing and the fact that real wings typically undergo flapping and twisting motions during flight. There are many computational and numerical studies of air flows on flapping bird’s wings at low Reynolds numbers, but relatively few experimental studies due to the difficulty of modelling a realistic flapping motion. In this article, the flow on a real flapping bird wing is visualised in a teaching demonstration using high-speed photography. It is found that the main features of the flow can be observed and that the demonstration is a teaching aid for assisting student understanding of principles of aerodynamics. The possibility of incorporating the demonstration into a standard teaching course is discussed, with relevant teaching objectives highlighted. In conclusion, it is recommended that the demonstration could be useful as part of a course on aerodynamics, with further follow-up demonstrations and studies suggested.