No abstract

Vortex asymmetry on axisymmetric pointed forebodies at high angles of incidence results in side forces and yawing moments even in symmetrical flight. This can adversely affect the yaw control characteristics of a flight vehicle and limit maneuverability. An experimental investigation of vortex asymmetry was carried out on a 12° semi-apex angle cone at high angles of incidence at low speeds. Measurements include forces and moments using a six-component strain gage balance and stereoscopic particle image velocimetry to obtain three-dimensional flow field characteristics. Results show that slender cones at high angles of incidence show bi-stable behavior with roll orientation. Vortex asymmetry is initiated at very close to the cone tip due to the presence of micro-imperfections on the cone surface and develops into asymmetric vortex sheet downstream along the conical body. The strength of the fully developed vortex moving away from the surface is nearly double of the vortex residing close to the surface, leading to large magnitude side forces and yawing moments.= cone base area, π(D/2) 2 C s = coefficient of side force, SF/(0.5ρU ∞ 2 A b ) C x = aerodynamic force coefficient , F/(0.5ρU ∞ 2 A b ) C m = aerodynamic moment coefficient , F/(0.5ρU ∞ 2 A b D) D = cone base diameter F = aerodynamic force r = azimuthal plane distance from cone centerline Re D = Reynolds number SF = side force U ∞ = freestream velocity U XY = cross-flow velocity x = axial distance from nose V = in-plane velocity component (Y-direction) W = in-plane velocity component (Z-direction) α = angle of incidence ρ = density φ = roll angle

No abstract