Water Tunnel Flow Visualization Study of a 4.4% Scale X-31 Forebody

Abstract

A water-tunnel test of a 4.4 percent--scale, forebodyonly model of the X-31 aircraft with different forebody strakes and nosebooms has been performed in the Flow Visualization Facility at the NASA Dryden Flight Research Center. The focus of the study was to determine the relative effects of the different configurations on the stability and symmetry of the high-angle-ofattack forebody vortex flow field. The clean, noseboom-off configuration resisted the development of asymmetries in the primary vortices through 70° angle of attack. The wake of the X-31 flight test noseboom configuration significantly degraded the steadiness of the primary vortex cores and promoted asymmetries. An alternate L-shaped noseboom mounted underneath the forebody had results similar to those seen with the noseboom-off configuration, enabling stable, symmetrical vortices up to 70° angle of attack. The addition of strakes near the radome tip along the waterline increased the primary vortex strength while it simul...