Comparative assessment of Reynolds-Averaged Navier-Stokes turbulence models for external aerodynamics of a 155-mm artillery projectile

This work presents a comparative numerical investigation of Reynolds-averaged Navier–Stokes turbulence models applied to the external aerodynamic analysis of a 155-mm artillery projectile. Axisymmetric compressible computational fluid dynamics simulations were performed using the Spalart–Allmaras, standard k − ε , and Shear Stress Transport (SST) k − ω turbulence models under subsonic, transonic, and supersonic flight conditions. The numerical methodology employed finite volume discretization, structured meshes with near-wall refinement, and a density-based implicit solver. Mesh independence was evaluated using the Grid Convergence Index methodology. The aerodynamic drag coefficients obtained from the computational fluid dynamics simulations were compared with reference data generated using PRODAS software. Statistical metrics, including mean absolute percentage error, root mean square error, and coefficient of determination ( R 2 ), were used to quantify the agreement between numerical predictions and reference data. The results demonstrated that the SST k − ω model provided the best overall agreement with PRODAS predictions, achieving a mean absolute percentage error of 3.47% and an R 2 value of 0.9594. The standard k − ε model also showed satisfactory capability in reproducing the drag coefficient trend throughout the investigated Mach range, whereas the Spalart–Allmaras model presented larger deviations. Overall, the applied numerical methodology demonstrated satisfactory capability for predicting and analyzing the external ballistic aerodynamics of artillery projectiles.