Numerical simulation of flow characteristics of a mechanical iris-type adjustable nozzle for solid rocket motors

Abstract This study conducts numerical simulations of the flow characteristics of a mechanical iris-type adjustable nozzle under steady-state conditions, using a periodic grid to reduce computational cost. The flow characteristics and axial forces around the insert body at three different throat areas are analyzed. The engine thrust loss is calculated. The results indicate that as the throat area increases, the total pressure loss due to the shock system in the nozzle throat remains approximately 21% along the axial direction. Meanwhile, the axial force acting on the insert body decreases, and the static pressure distribution on both sides remains consistent. However, the engine’s thrust loss rises significantly and continues to increase.