Experimental investigation of side force control on cone-cylinder slender bodies with flexible micro balloon actuators

Side forces on slender bodies of revolution at medium to high angles of attack (AOA > 30°) has been known from a large number of investigations. Asymmetric vortex pairs over a slender body are believed to be the principle cause of the side forces. Under some flight conditions, this side force may be as large as the normal force acting on the slender body. In this paper, experimental results are presented for side force control on a cone-cylinder slender body by using microfabricated balloon actuators. The micro balloon actuators are made of polydimethylsiloxane (PDMS) elastomer by using micro molding techniques. They can be packaged on curve surfaces of a cone-cylinder slender body. As actuator is actuated, the micro balloon actuator inflates about 1.2 mm vertically, which is about 2.4% of the cylinder diameter D (=50 mm) of the cone-cylinder slender body. Micro balloon actuators are actuated at different roll angles of a cone-cylinder slender body. Aerodynamic force measurement results indicate the effects of micro balloon actuators vary at different actuation locations on the cone-cylinder slender body. The side forces can be significantly reduced if the actuators are actuated in the weak vortex side (the side corresponding to the asymmetric vortex which is far from the surface) and actuation angles are located at about 50–60° (the actuation angle here is measured from stagnation line of the incidence plane toward weak vortex side direction). Significant changes are noticed from the surface pressure, as well as leeside vortex flow field, measurement. Micro balloon actuators change nose shapes of the slender body which decide adverse-pressure-gradient values and directly influence the origin of the separation lines and characteristics of the separated vortices over the leeside surface.