Sources of High Alpha Vortex Asymmetry at Zero Sideslip

Abstract

A review of existing experimental results for slender bodies and delta wings, tested at high angles of attack, reveals that no physical evidence exists that vortex asymmetry on slender pointed bodies or delta wings has ever occurred through the so-called hydrodynamic instability process. It will be shown that in the numerous tests performed, asymmetric flow separation and/or asymmetric flow reattachment, were the flow mechanisms triggering the vortex asymmetry. Slender wing rock is found to result from a basic lack of roll damping, existing for attached leading-edge vortices, and the vortex-asymmetry is generated at nonzero roll angle, i.e., for asymmetric flow conditions. Nomenclature b = wingspan c = reference length, d CQ = delta wing center chord d = maximum diameter of body of revolution € = rolling moment, coefficient C€ = €/(p00U£/2) Re = Reynolds number based on d and freestream conditions S — reference area, ird2/4 or projected wing area U = horizontal velocity Y = side force, coefficient CY = Y/(pJJl/2) a = angle of attack OA = aPex half-angle Oc = cone half-angle A = leading-edge sweep p = air density = body roll angle Subscripts A = apex c = cone oo = freestream conditions