Flow Control on a Swept Back Cylinder of Finite Aspect Ratio

Force and moment measurements on a 60º swept back cylinder of finite aspect ratio indicated that large flow asymmetry is created by local injection of momentum in a direction that is perpendicular to the cylinder’s axis and inclined at 20º to the surface. The cylinder contains two actuators that divided the span into three segments of similar length and whose azimuthal location could be changed at will. The experiments were performed at Reynolds number of 3 x 10⁵ and roughness dots were distributed throughout the surface to ensure that the flow was fully turbulent. The interaction was investigated using surface pressure measurements, stereoscopic PIV and oil flow visualization. Since the jet was injected from a small nozzle representing a point source, its azimuthal location on the cylinder’s surface was very significant. When the actuator was azimuthally close to the natural separation line, the emitted jet was redirected by the strong spanwise flow on the cylinder. The jet-crossflow interaction seems to have reattached one vortex (in the lee of the cylinder) to the cylinder surface, generating a sufficiently large side force capable of yawing the cylinder to a new equilibrium location.