Interaction of missile nose-tip vortices with a control surface

Abstract

The interaction between vortices forming at the nose tip of a missile model and a single fin located down the axis of the model was investigated experimentally for a range of axial fin positions [2.6 < —180 deg), and Reynolds number (6 x 103 < Red < 3.4 x 10 4) for two angles of attack, 30 and 45 deg. Symmetric, attached vortices formed over the model at the lower angle of attack, whereas the vortices were asymmetric when the angle of attack was increased to 45 deg. The interaction was documented using flow visualization and mean pressure measurements on the fin surfaces. The pressure data were used to compute the normal force coefficients on the fin. The effects of the interaction on the fin are described; in particular, the similarities and differences in the flowfield at the two angles of attack are discussed for one axial fin location [(x/d)f = 7.1]. Nomenclature Cfp = normal force coefficient, port surface of fin C/.v = normal force coefficient, starboard surface of fin Cft = total normal force coefficient Cp = pressure coefficient d = model diameter Red = Reynolds number based on model diameter x = axial distance along model from nose tip x' = axial distance from leading edge of fin (x/d)f = dimensionless distance from nose to leading edge of fin y' = transverse (spanwise) distance from root chord of fin a = pitch angle (p azimuthal angle of fin, measured from leeward ray