Numerical investigation of dynamic characteristics of dual throat nozzle and bypass dual throat nozzle in thrust vectoring starting process

The Bypass Dual Throat Nozzle(BDTN) is a novel fluidic Thrust Vectoring(TV) nozzle,it switches to TV state by opening the valve in the bypass. To greatly manipulate the BDTN, the dynamic characteristics in the TV starting process should be analyzed. This paper conducts numerical simulations to grasp the variation processes of performances and the flow field evolution of BDTN and Dual Throat Nozzle(DTN). The dynamic responses of TV starting in typical DTN models are investigated at first. Then, the TV starting processes of BDTN in different Nozzle Pressure Ratio(NPR) conditions are simulated, and the valve opening durations(T) are also considered. Before the expected TV direction is achieved in the DTN, the jet is deflected to the opposite direction at the beginning of the dynamic process, which is called the reverse TV phenomenon.However, this phenomenon disappears in the BDTN. The larger injection width of DTN intensifies unsteady oscillations, and the reverse TV phenomenon is strengthened. In the BDTN, T determines the delay degree of performance variations compared to the static results, which is called hysteresis effect. At NPR = 10, the hysteresis affects the final stable performance of BDTN. This study analyses the dynamic characteristics in DTN and BDTN, laying a foundation for further design of nozzles and control strategies.