On the turbulent wake of the actuated fluidic pinball: dynamics, bifurcations and control authority

Abstract

This work presents the first comprehensive experimental and numerical study of the turbulent wake of the actuated fluidic pinball across a large actuation range. The fluidic pinball consists of three equal circular cylinders arranged on the vertices of an equilateral triangle, pointing upstream in uniform flow, serving as a canonical benchmark for control-oriented reduced-order modeling and nonlinear control design. While previous studies focused on laminar two-dimensional Reynolds number regimes, we investigate the symmetrically actuated turbulent regime at Re = 9100. The upstream cylinder remains stationary, while the two downstream cylinders rotate with equal and opposite angular velocities. A broad range of base-bleeding and boat-tailing actuation parameters is explored using time-resolved particle image velocimetry and aerodynamic force measurements, complemented by Reynolds-averaged Navier-Stokes simulations. The results reveal that the turbulent wake can be described by a three-dimensional actuation manifold exhibiting two inverse pitchfork bifurcations. In the boat-tailing limit, reduced control authority and a new low-frequency shedding state are observed.