Counterflow Thrust Vector Control of Subsonic Jets: Continuous and Bistable Regimes

Fluidic thrust vectoring of a subsonic jet was examined by the asymmetric application of countere ow to the jet shear layers. When countere ow is applied to one side of a 4:1 aspect ratio rectangular jet in the proximity of a control surface, the shear-layer entrainment characteristics are altered asymmetrically giving rise to a cross-stream pressure gradient and e ow vectoring. Thrust vector control up to 20 deg was possible at Mach numbers up to 0.5 using countere ow. Two regimes of e uidic control were identie ed, a continuous regime and a bistable one. During continuous vectoring, proportional control could be achieved between jet response and the pressure conditions established in the countere owing stream. However, under certain circumstances, proportional control was lost leading to jet bistability. Since such bistability is undesirable for aircraft control applications, the phenomenon was studied in detail. A parametric study of the collar geometry was used to minimize jet attachment and expand the operating domain over which proportional control could be maintained.