Abstract: Two-dimensional hypersonic inlets with a forward-swept sidewall and an aft-swept sidewall are tested experimentally and simulated numerically to examine the effect of sidewall geometry on the starting characteristics of a two-dimensional hypersonic inlet. The result shows that the forward-swept sidewall inlet exhibits significantly better capability of self-starting. The bottom wall pressure distribution, surface oil flow pattern and numerical result all reveal that the unstarted flowfield structures of the two inlets are quite different. Large-scale flow separation occurs at the bottom wall side in the unstarted flowfield of an aft-swept sidewall inlet, while it is at the cowl side in the unstarted flowfield of a forward-swept sidewall inlet because of the constraint on the separation bubble by the forward-swept sidewall leading edge. The cowl side boundary layer is much thinner than the bottom wall side boundary layer and it can resist stronger reverse pressure gradient before the separation occurred. That accounts for the fact that the forward-swept sidewall inlet has better starting characteristics.

Key words: hypersonic, inlet, sidewall geometry, starting characteristics, free-jet, numerical simulation