71th Annual Meeting of the APS Division of Fluid Dynamics (November 18, 2018 — November 20, 2018)

V0031: Transition from Order to Chaos in the Wake of a Flapping Airfoil

Authors

• CHANDAN BOSE, Ph.D. Scholar, Dept. of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036, India.
• SAYAN GUPTA, Professor, Dept. of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036, India.
• SUNETRA SARKAR, Professor, Dept. of Aerospace Engineering, Indian Institute of Technology Madras, Chennai 600036, India.

DOI: https://doi.org/10.1103/APS.DFD.2018.GFM.V0031

Flapping airfoils spawn a variety of wake patterns in their trail with variation in kinematic parameters such as frequency and amplitude of oscillation. Characterizing such complex patterns would enrich the understanding of the underlying unsteady aerodynamics of different swimming and flying biological species and their load generation capabilities. In the low Strouhal number regime, the wake remains periodic . As the Strouhal number is increased, the wake loses the spatial symmetry and the wake undergoes a deflection in the upward or downward direction. The deflected jet switches its direction with the further increase in Strouhal number. A phenomenological transition from order to chaos is observed in the flow topology at very high Strouhal numbers. The aperiodic trigger which is fawned by irregular leading-edge separation gets propagated in the form of spontaneous formation of vortex couples and various fundamental vortex interactions making the flow-field unpredictable and dramatically different from one cycle to another.