Chaotic Onset in the Flow Past a Flapping Foil Depends on the Free-Stream Reynolds Number

Dynamical route to chaos and the corresponding transitional onset is very crucial for the efficient design of flapping-based aerial and underwater vehicles. Different size, shape, and flight speed of the wide range of natural flyers/swimmers manifest different Reynolds numbers (Re). The present study investigates the effect of Re on the dynamical behaviour of the flow field past a plunging elliptic foil. Numerical simulations have been carried out using a discrete forcing immerse boundary method-based in-house flow solver. Different non-linear time series tools such as phase portrait and wavelet spectra have been employed to identify the dynamical characteristics of the flow field. Distinct difference is observed for the qualitative dynamics of the flow field at Re = 100 and Re = 300, though the dynamical plunge velocity (κh) was kept constant.