Flare-Control Effectiveness at Hypersonic Speeds

Abstract

The effects of flare control on the aerodynamic characteristics, performance, and stability of a cylindrical body under laminar and turbulent boundary layer conditions have been studied experimentally and computationally. The experimental study has been carried out in a hypersonic gun tunnel at a Mach number of 8.2 and a Reynolds number of 158,100, based on the cylinder diameter, at flare angles 0, 5, 10, 15, 20, 25 and 30 degrees and at pitch angles of −12 to 12 deg for the 10 deg flare case only. The surface flow was studied using the oil-dot technique. Some information regarding the shock layer was obtained from schlieren pictures. The effects of turbulence on onset of separation were also deduced from pressure measurements over the cylinder and the flare. The forces were measured with a three-component balance equipped with semiconductor strain gauges. The effects of centre of gravity (CG) location on the aerodynamic characteristics and in particular on the C_Mαwere examined. The results under turbulent conditions and zero-incidence were compared with numerical simulations performed using a 3-D time-marching Navier-Stokes code. The magnitude of the separated region, the minimum flare angle required to induce separation, and the effects of small-scale separation are detailed.