Numerical strategies for a full time-scale transient simulation of progressive-burning solid rocket motors’ internal ballistics

Abstract

Accurate prediction of internal ballistics in solid rocket motors (SRMs) is essential for reliable design but remains challenging due to the transient nature of combustion and nozzle flow. While steady-state models are computationally efficient, they fail to capture time-dependent effects such as shock wave formation. This study presents a full time-scale CFD simulation of progressive-burning sugar-based propellant, using ANSYS Fluent with both pressure-based and density-based solvers. A Realizable k–ε turbulence model with non-equilibrium wall functions and non-reactive species transport formulation was applied in a fixed-mesh approach. Simulations reproduced the complete burn time of several experimental tests. Both solvers captured shock wave dynamics consistently, but the pressure-based solver achieved convergence within 4 days, whereas a density-based solver would require 10 days. Comparisons with experimental thrust coefficient highlighted sensitivity to burn-rate data, underscoring its critical role in quantitative accuracy. The results demonstrate that pressure-based solvers provide a practical, resource-efficient strategy for iterative SRM design without compromising essential flow physics.