Experiments on a fluidic pinball: wake dynamics in the chaotic regime

Over the past decade, the fluidic pinball has become a valuable benchmarkfor studying flow control strategies. The configuration consists of three independently rotating cylinders positioned at the vertices of an equilateral triangle, with the flow directed perpendicularly to one of its sides. The cylinder rotation rates serve as the control inputs, while velocity sensors located in the wake provide the outputs. Despite its geometric simplicity, the wake behind the fluidic pinball displays complex interactions of multiple frequencies and nonlinear dynamics, making it an excellent test case for the development and evaluation of control laws. While numerous studies have been performed numerically at low Reynolds numbers, experimental literature is limited, mainly due to the associated engineering challenges.

This study presents the findings from wind tunnel experiments on a fluidic pinball in the chaotic regime (1333 ≤ Re ≤ 3333). Planar two-component particle image velocimetry (PIV) is employed to capture the velocity field while the velocity time traces are obtained from hot-wire anemometry and laser Doppler velocimetry (LDV). The stochastic bistable dynamics in the wake is characterized and its sensitivity to external disturbances is demonstrated. Coherent structures in the wake along with the associated temporal dynamics and their physical implications are analyzed for both the stationary pinball and the flow with steady, open-loop forcing. The effect of blockage and evolution of 3D structures in the forced wake is discussed. A brief overview of the architecture set up for real-time control is also presented.

Speaker : Dr. Aditya Desai

Biography :

Dr. Aditya Desai is a post-doctoral researcher at the Laboratory of Interdisciplinary Numerical Sciences (LISN)- CNRS, Orsay,France working towards Reinforcement Learning-based control of a fluidic pinball. He completed his Master’s and PhD from the Department of Aerospace Engineering, IIT Kanpur. His research interests are in the domain of experimental aerodynamics, reduced order modelling and flow control,  wakes, vortex induce vibration and sports aerodynamics. He completed his BTech in Aerospace Engineering at IITK in 2009.