SUMMARY

Aerodynamic steering forces and moments on a wind tunnel model of an axisymmetric bluff body are altered by induced local attachment of the separated base flow. The model is suspended in the wind tunnel by eight thin wires for minimal support interference within the wake. Each wire is instrumented with a miniature strain gage sensor for direct dynamic force measurements. Control is effected by an array of synthetic jet actuators that emanate from narrow, azimuthally-segmented slots, within a backward facing step. In the first set of experiments, the array of synthetic jets is distributed around the perimeter of the circular tail end which extended into a Coanda surface. The fluidic actuation results in a localized, segmented vectoring of the separated base flow along the rear Coanda surface and induces asymmetric aerodynamic forces and moments to effect steering during flight. In addition, transitory modulation of the actuation waveform of multiple actuators around the tail leads to the generation of significant dynamic side forces of controlled magnitude and direction with the potential utility for flight stabilization and fast maneuvering. The second set of experiments placed the array of synthetic jets upstream of a mid-body axisymmetric cavity, issuing over a Coanda surface. In this case, it is shown that a single jet generates a quasi-steady, nearly matched force couple at the upstream and downstream ends of the cavity. Furthermore, transitory activation of multiple jets can be used to control the onset and sequencing of the couple forces and therefore the resultant force and moment. In both sets of experiments, the aerodynamic effects are characterized using direct force, hot-wire and PIV measurements.