Experimental investigations of the vortex flow behind a circular cone at high angles of attack

Abstract

The vortex flow which develops on a flying aircraft or missile becomes asymmetric at some large incidence. This asymmetric vortex configuration 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 Re = 142,000 from a - 15 deg to 35 deg. Asymmetric pressure distribution due to vortex-flow asymmetry occurs on the lee-side, at a> 17 deg. Resulting in large side force. Inserting a longitudinal fm between the vortices at a = 25 deg and 35 deg appreciably reduces the asymmetry of the vortices and the side force. The angle of attack, a , at which the lee-side vortex system becomes asymmetric was determined, by smoke-flow visualization, as a function of free-stream Reynolds number Re, for Re = 5,000 to 202,000 (based on cone base diameter). The results show a clear dependence of a on Re and on surface conditions.