| The vortex flow which develops on a flying aircraft or missile becomes asymmetric at some large incidence. This asymmetric vortex configurations can give rise to significant undesirable side forces and yawing moments.; The vortex-flow asymmetry was experimentally studied on a circular cone in the low-speed wind tunnel of KFUPM, at high angles of attack. Circumferential surface-pressure distributions were measured, at {dollar}Resb{lcub}D{rcub} = 142,000{dollar} from {dollar}alpha{dollar} = 15 deg to 35 deg. Asymmetric pressure distribution due to vortex-flow asymmetry occurs on the lee-side, at {dollar}alpha geq 17{dollar} deg. resulting in large side force. Inserting a longitudinal fin between the vortices at {dollar}alpha = 25{dollar} deg and 35 deg appreciably reduces the asymmetry of the vortices and the side force.; The angle of attack, {dollar}alphasb{lcub}onset{rcub}{dollar}, at which the lee-side vortex system becomes asymmetric was determined, by smoke-flow visualization, as a function of free-stream Reynolds number {dollar}Resb{lcub}D{rcub}{dollar}, for {dollar}Resb{lcub}D{rcub} = 5,000{dollar} to 202,000 (based on cone base diameter). The results show a clear dependence of {dollar}alphasb{lcub}onset{rcub}{dollar} on {dollar}Resb{lcub}D{rcub}{dollar}, and on surface conditions. |
