Understanding Flapping Flight through PIV Measurements on a Butterfly Simulating Model

Abstract

Velocity field of a model-„monarch‟ butterfly wing is measured using Particle Image Velocimetry (PIV). Details of the unsteady flow and vorticity field are obtained at different chord cross-sectional plane of the scaled wings to understand the dynamics of butterfly flight. The model being studied resembles the clap and fling mechanism of butterflies. The wing flexibility introduces feathering effect in the kinematics. The mechanisms that produce high lift and considerable thrust during the flapping motion are identified. Effect of the Reynolds number on the flapping flight is studied by varying the wing size and the flapping frequency. Measurements are carried out to study the general mechanism of generation of aerodynamic forces. The effects of rotational twisting (feathering motion) at the stroke reversals which is very crucial in lift and thrust generation, has been studied. The effect of clapping motion at the end of upstroke has been observed. The aim here is to observe the aerodynamic forces and their causes at zero forward velocity and notice the difference with different Reynolds number (Re) and flapping frequency (f).