Fluidic thrust vectoring for low observable aircraft

The work presented in this paper deals with the development of a coflow fluidic thrust vectoring system for use on a low observable unmanned air vehicle operating in the subsonic flight regime. Two approximately 1/10 th scale fluidic thrust vectoring demonstrator rigs were designed and built in order to investigate the effect of various geometric variables on thrust vectoring effectiveness. These included secondary gap height, dh, and Coanda surface diameter, ∅. Load measurements were obtained using a six component overhead balance. The thrust vector force, Fz,tv, was made non-dimensional using the thrust force of the nonvectored primary jet, F x , to give a thrust vector coefficient, Cz. Tests were carried out over the mass flow ratio range 0 � m s /m p < 0.13 which corresponded to a momentum flow ratio range of 0 � Ms/Mp < 0.4. A computational investigation for 2D flow was also undertaken primarily to aid in the design of the experimental demonstrator rigs and smoke flow visualisation techniques were used to further investigate the flow characteristics of a non-vectored and a vectored primary jet. The investigation shows that both the experimental and computational results obtained follow a similar trend line. A ‘dead zone’ appears at low mass flow ratios in which no control can be achieved. There then follows a control region in which continuous thrust vector control can be achieved followed by a hypothetical saturation region. The secondary jet blowing rate, the Coanda surface diameter and the primary nozzle to secondary nozzle height ratio are seen to determine whether effective and efficient fluidic thrust vectoring can be achieved. Nomenclature Ap Cross sectional area of primary jet m 2 As Cross sectional area of secondary jet m 2