Aerodynamic flow-vectoring of a planar jet in a co-flowing stream

Abstract

The vectoring of an incompressible, two-dimensional jet in a co-flowing stream is investigated by means of direct numerical simulation. The control input used to stimulate jet vectoring is accomplished through distributed suction from blunt-faced lips at the exit of the jet. The thrust vector methodology is based on suppression of global instabilities in the wake-shear layers formed between the co-flow and the jet. Once a critical suction volume flux needed to suppress these global instabilities is exceeded, local flow control can be realized through varying the distribution of suction across the base of the jet lips. It is found that the critical suction flux scales primarily with the ambient co-flow, not with the jet speed, and that lift-to-thrust ratios exceeding 15% can be realized. The effects of jet Reynolds number, jet-to- ambient velocity ratio, boundary-layer thickness, and geometric parameters on various performance characteristics are examined. It is also shown that the asymmetric flow control approach used for vectoring the jet can also be implemented in a symmetric configuration to enhance jet spreading. Significant increases in jet spreading can be realized when the symmetrically applied suction flux is sufficient to stimulate the sinuous mode of instability of the jet such that energetic apping motion ensues.