Reynolds Number Effect on Aerodynamic and Starting Characteristics of a Two-Dimensional Hypersonic Inlet

The Reynolds number effect induced by model scaling and inflow conditions will affect the aerodynamic and starting characteristics of a two-dimensional hypersonic inlet. This effect is investigated through a numerical simulation method. First, the numerical simulation method is validated through experimental data. The static pressure from the numerical simulation method agreed well with wind tunnel tests. Then, this simulation method is used to study the Reynolds number effect on a two-dimensional hypersonic inlet caused by the model scaling and inflow conditions. The numerical simulation results indicate that as the Reynolds number decreases from 4.86 × 106 to 9.71 × 104 with model scaling increases from 1 to 1/50, the relative boundary layer thickness at the entrance of the inlet increases from 10.4% to 21.2%; as the flight altitude increases from 25.5 km to 36.5 km, which causes the Reynolds number to decrease from 5.67 × 106 to 1.07 × 106, the relative boundary layer thickness at the entrance of the inlet increases from 9.8% to 13.2%. Finally, the Reynolds number effect on the aerodynamics and starting characteristics caused by these two different factors are compared. The results show that the effect of scaling the model is similar to the effect of changing the altitude. As the relative boundary layer thickness increased by 1.0%, the total pressure recovery at the throat section decreased by 0.8%, and the inlet starting Mach number increased by 0.1.