Purpose - The purpose of this paper is to analyze the flowfield structure and performance of dual secondary injection system for thrust vectoring in a convergent-divergent nozzle and to compare it with a single secondary injection system. Design/methodology/approach - Dual secondary injection for thrust vectoring in a convergent-divergent nozzle is studied by solving three-dimensional Reynolds-averaged Navier-Stokes equations by the means of Fluent. Realizable k-epsilon turbulent model with enhanced wall-treatment approach is used for viscous model. Density-based solver and explicit scheme are employed in the computational model. In order to study the effect of injection location on the flowfield, distance between ports is considered as the key variable. Findings - Results show that under some circumstances, dual secondary injection system is more effective than a single injection system with the same mass flow rate. The study shows that when the distance between two ports is 8.5 times of the injection port's diameter (or more) and in the same time the first injection port is at least 1 throat diameter far from the nozzle throat, this system will show a better performance. In addition, this system reduces the probability of bow shock impingement to the opposite wall and consequently, the side force production has less limitation. Practical implications - Dual secondary injection for thrust vector control (SITVC) needs less secondary flow and therefore it makes less reduction in the primary thrust. It means that for a specific primary thrust, less mass fuel is needed which makes it more economic regarding the traditional SITVC systems. Originality/value - The paper's value lies in using a three-dimensional model to study the effect of two ports distance on SITVC performance and comparison among the performance of dual and single injections when there is an impingement.
