Hypersonic aeroheating characteristics of leading edges with different nose radii

The applications of leading edges with different nose radii in hypersonic flights require investigations on their aeroheating characteristics in various gas flow regimes. For a detailed numerical study of this problem, the direct simulation Monte Carlo method is used to compute the wall heat fluxes and flowfield information for hypersonic flows over a series of leading-edge profiles. The stagnation point heat flux increases as the nose radius decreases but reaches a finite value when the nose radius approaches zero. This variation characteristic conflicts with the formulas based on continuum flow theory. A further analysis of the flowfield structures illustrates the continuum-breakdown phenomena caused by the strong local nonequilibrium in the vicinity of sharpened leading edges, where a molecular kinetic description of the gas flow is necessary. The distribution functions of molecular velocity at the stagnation points of different leading edges are presented and successfully explain the relation between the stagnation point heating and the nose radius.Afast estimation formula for the stagnation point heat transfer coefficient is proposed. It applies to various flow regimes and gives results that agree well with the present numerical results and the existing experimental data.