Closed-Loop Flow Control of the Oscillations of a Free-Suspended Cylinder at Low Reynolds Numbers

摘要

Helicopters carrying slung loads are plagued by problems in flightstability at moderate speeds. The slung load oscillations are detrimental atfull scale flight conditions. The unstable oscillations translate to missiontrade-offs and therefore are of interest to overcome. Active flow controltechnology presents a unique ability to create the necessary aerodynamicstability at low cost, weight, complexity, energy and size. This study isfocused on reducing the natural oscillations of a scaled model of a cylindricalslung load suspended in a wind tunnel. The research employs Fluidic-piezoelectricactuators to accomplish the stated objective. The dynamics of thebaseline, scaled, uncontrolled model are in good agreement with flight testdata. The yaw oscillations characteristics are compared with a spectrum ofclosed-loop control configurations that were designed and implementedover a range of tunnel speeds. Each configuration commands the actuatorsto induce fluidic excitation through two miniature openings at the cylindersummit near the side-edges of the finite span cylinder. The experimentsdemonstrate the feasibility of the solution, presents detailed data anddiscusses the utility of the technology to solve real world challenges. Futureresearch and application path are also discussed.