Leaf flutter by torsional galloping: Experiments and model

When wind blows on trees, leaves flutter. The induced motion is known to affect biological functions at the tree scale such as photosynthesis. This paper presents an experimental and theoretical study of the aeroelastic instability leading to leaf flutter. Experiments in a wind tunnel are conducted on ficus leaves (Ficus Benjamina) and artificial leaves. We show that stability and flutter domains are separated by a well-defined limit depending on leaf orientation and wind speed. This limit is also theoretically predicted through a stability analysis of the leaf motion.