Axisymmetric and three-dimensional flow simulation of a mixed compression supersonic air inlet

The flow through an axisymmetric supersonic mixed-compression air inlet has been simulated numerically to investigate the effects and the necessity of the three-dimensional (3D) modeling in comparison with the axisymmetric one. For this purpose, a supersonic inlet has been simulated numerically via axisymmetric and 3D CFD solvers, using the steady state Reynolds-averaged Navier-Stokes equations along with the SST k-ω turbulence model, for a free-stream Mach number of 2.0 and at zero degrees angle of attack. The grid for the 3D cases was a 14.4-degree sector, instead of a 360-degree domain one, with rotational periodic boundary condition for the side boundaries. The results show that both static and total pressure distributions match well with the experimental data for both the axisymmetric and the 3D simulations. If the prediction of performance parameters is the main goal of simulations, it seems that the axisymmetric simulation provides adequate accuracy, and the 3D simulation one is not the best choice. The 3D numerical simulation results in an in-depth study on the supersonic inlets, including the shock wave-boundary layer interaction, the location of the terminal normal shock wave, and consequently the separation point. For an axisymmetric supersonic inlet in an axisymmetric flow condition, 3D effects are not strong enough to have a significant influence on the inlet performance for all operational conditions. However, it seems that 3D effects play an important role in both critical and supercritical operating conditions during the steady state operation.