Closed-loop flow control of the roll and yaw oscillations of a free‑suspended cylinder at low reynolds numbers

Helicopters carrying slung loads are plagued by problems in flight stability at moderate speeds due to slung load oscillations. The unstable oscillations translate to mission trade-offs and therefore are of interest to overcome. Active flow control technology presents a unique ability to create the necessary aerodynamic stability at low cost, weight, complexity, energy and size. This study is focused on reducing the natural oscillations of a scaled model of a cylindrical slung load suspended in a wind tunnel with fixed anchor point. The research employs Fluidic-piezo-electric actuators to accomplish the stated objective. Previous, recent research in this area by our group has focused on characterizing slung load dynamics and reducing the yaw oscillations. The current follow on study expands this to encompass both yaw and roll swinging motion. The oscillation characteristics are compared with a spectrum of closed-loop control configurations. Each configuration commands the actuators to induce fluidic excitation through two miniature openings at the cylinder summit near the side-edges of the finite span cylinder as well as four additional opening near the leading and trailing edge of the cylinder side-caps. The experiments demonstrate the feasibility of the current flow control approach presents detailed data and discusses the utility of the technology to solve real world challenges. Future research and application path are also discussed.