Flow-Field Design and Analysis within Single and Dual-Bell Propulsion Nozzles

Abstract

The present study focuses on the design and numerical analysis of a dual-bell propulsion nozzle, and compares its performance and flow-field characteristics with those of a conventional single-bell nozzle having the same area ratio at the throat and exit. The I. _________________________________________________________________________________________________________________ I. Abdou, M. Flow-Field Design and Analysis within Single and Dual-Bell Propulsion Nozzles 2 dual-bell nozzle, known for its altitude-adaptive capabilities, was modeled to exploit its two distinct operating modes: a sea-level mode with flow separation, and a high-altitude mode with flow attachment along the walls. Steady-state simulations were carried out using “ANSYS Fluent” platform that solves the Reynolds-Averaged Navier–Stokes (RANS) equations in 2-D axisymmetric form, with the k-ω SST turbulence model used to close the system. Key flow parameters such as pressure and Mach distributions along the performance characteristics, were evaluated. Compared to the single-bell configuration, the dual-bell nozzle exhibits more stable flow behavior under over-expanded conditions and delivers better overall thrust efficiency under varying ambient conditions. This comparative study highlights the potential of dual-bell nozzles to enhance the performance of the first stages of next-generation launch vehicles.