Forebody Articulation at High Angles of Incidence

Abstract

An experimental investigation was carried out to understand the effect of forebody articulation on the aerodynamic characteristics and the flowfield development over a slender body at high angles of incidence. The experiments were carried out at the Florida A&M University and Florida State University low-speed wind tunnel over a range of forebody deflection ([Formula: see text], [Formula: see text], and [Formula: see text]) and flow conditions. The results show that a positive forebody deflection increases the normal-force coefficient, whereas a negative forebody deflection decreases the normal-force coefficient at high angles of incidence. Pitching moment characteristics showed that all forebody deflections tested produce a pitching moment despite minimal normal force at low angles of incidence. Lateral aerodynamic characteristics showed that the side-force onset angle does not solely depend on the semi-apex angle of the forebody (as predicted for axisymmetric slender bodies), and the role of the forebody-to-aftbody transition geometry in initiating vortex asymmetry is equally important. The particle image velocimetry results show that a positive forebody deflection increases the size, strength, and circulation of the vortices developing on the body, leading to an increase in aerodynamic forces and moments. The flowfield development for a negative forebody deflection is dominated by secondary shear-layer vortices originating from the forebody to aftbody junction.