Unsteady actuation and feedback control of the experimental fluidic pinball using genetic programming

The application of genetic programming for closed-loop wake stabilization downstream of a triangular cluster of three rotating cylinders, referred to as the fluidic pinball, is investigated experimentally. The implementation of unsteady actuation for control is considered and the benefits over steady control Raibaudo (Phys Fluids 32:015108, 2020) discussed. Experiments are performed at Reynolds number Re \(\approx \) 2200. Two-component planar PIV measurements and hot-wire anemometry are used to characterize the wake with and without actuation. Each cylinder is controlled independently, and the rotation speed is sinusoidally modulated. Linear genetic programming is implemented for the optimization of feedback controllers. Two objectives are considered: drag reduction or wake symmetrization, for which two cost functions \({\mathcal {J}}\) are defined. Open-loop control using sinusoidal modulation is performed to study the efficiency of unsteady actuation compared to constant rotation speeds. Genetic programming is shown to be more efficient than traditional methods for optimization of a large number of control parameters. For the fluidic pinball, optimal solutions are found to be more robust when compared to open-loop genetic algorithms.