Flat-ended circular cylinder in hypersonic rarefied flow

Abstract

The paper describes a study of the rarefied hypersonic flow about a flat-ended circular cylinder at various angles of attack. Examples of direct simulation Monte Carlo (DSMC) calculations for nonreacting nitrogen flows are presented, covering a range of Knudsen numbers from 0.034 to 1.84. These include the effects of rotational and vibrational energy exchange. Contour plots of density and temperature show the structure of the disturbed flowfield. For zero angle-of-attack flows, the density and rotational temperature predictions are compared with measurements made in a hypersonic wind tunnel at a Mach number of about 25 for a range of Knudsen numbers. Close agreement between the two is seen, although a lag in rotational temperature suggests that the coupling to this mode is underestimated. The DSMC calculations have been extended to cover angles of attack up to 40 deg. Flowfield and surface flux patterns are presented for these cases. For the denser flows, the maxima in heat transfer occur away from the plane of symmetry.