The rarefaction effects in the problem of hypersonic flow around a profile with blunted leading edge are studied in the flow regimes when the edge bluntness radius is comparable with the mean free path in the free stream. The flow around a cylindrically blunted thick plate at zero incidence was modelled numerically in the transitional regime by using the direct simulation Monte Carlo method, the finite-difference solution of the kinetic equation of the relaxation type (the ellipsoidal statistical model), and the solution of the Navier - Stokes equations. It is shown that for the Knudsen numbers in terms of the bluntness radius below 0. 1, the Navier - Stokes equations can be applied successfully for viscous flow description behind the shock wave provided that the initial rarefaction effects are taken into account via the slip and temperature jump boundary conditions on the plate surface. For Knudsen number of about 0. 5, the rarefaction effects are more appreciable; in particular, a substantial anisotropy of the distribution function takes place, but the Navier - Stokes equations yield, as before, a qualitatively correct result. The initial stage of the boundary layer development in the edge vicinity has been studied. In the considered range of Knudsen numbers, the entropy layer near the edge is comparable with the boundary layer thickness. As the distance from the leading edge increases one observes the absorption of the entropy layer by the boundary layer. In the studied parameter range, the interaction between the boundary and entropy layers leads to a flow stability increase.
ASJC Scopus subject areas
- Nuclear and High Energy Physics