A clustering genetic algorithm for cylinder drag optimization

A real coded genetic algorithm is implemented for the optimization of actuator parameters for cylinder drag minimization. We consider two types of idealized actuators that are allowed either to move steadily and tangentially to the cylinder surface (" belts "), or to steadily blow/suck with a zero net mass constraint. The genetic algorithm we implement has the property of identifying minima basins, rather than single optimum points. The knowledge of the shape of the minimum basin enables further insights in the system properties and provides a sensitivity analysis in a fully automated way. The drag minimization problem is formulated as an optimal regulation problem. By means of the clustering property of the present genetic algorithm, a set of solutions producing drag reduction of up to 50% is identified. A comparison between the two types of actuators, based on the clustering property of the algorithm indicates that blowing/suction actuation parameters are associated with larger tolerances when compared to optimal parameters for the belt actuators. The possibility to use few strategically placed actuators in order to obtain a significant drag reduction was explored using the clustering diagnostics of this method. The optimal belt-actuator parameters obtained by optimizing the two-dimensional case have been employed in three dimensional simulations, by extending the actua-tors across the span of the cylinder surface. The three dimensional controlled flow exhibits a strong two-dimensional character near the cylinder surface, resulting in significant drag reduction. The problem of flow control has been the subject of many theoretical, experimental and computational studies in the last few decades. Control of the flow past a circular cylinder is considered as a prototypical problem of bluff body flow control. Several methodologies have been presented in the past in order to modify vortex shedding behind a circular cylinder, either with passive geometrical modifications and/or with an open loop steady forcing. A non-exhaustive list includes studies of the effect of a splitter plate attached to the cylinder studied, among others, by [4], [26], [2]; properly placed holes on the surface of a hollow cylinder are also found to yield a drag reduction [27]; another possible action is base suction/blowing [22] and rotational oscillations were studied by [24], [5]. This latter control action has been found to induce dramatic changes in the wake and a significant drag reduction. However, the proper integration of control devices in realistic applications requires significant experimentation in order to explore the vast …