Analysis of the high angle of attack aerodynamics on finned bodies with spinning nose tip strakes

Abstract

Large out-of-plane loads on slender axisymmetric bodies at high angles of incidence have been observed by numerous researchers. Steady loads can be generated by large, stable, asymmetric vortices which shed off the leeward side of the body. The out-of-plane loading is dependent on the formation of the vortices. For a given flight attitude, the vortices are steady. However, small disturbances in the upstream flow can. cause a reorientation of the vortex structure into a new steady formation. This leads to a different out-ofplane loading on the body. Due to this phenomena, prediction of the side forces, yawing moment, and rolling moment are extremely difficult, and control of tactical missiles at high angles of attack involves robust adaptive control systems which react to the changes in out-of-plane loading. If the slender body has wings and fins, the shed vorticity will interact with the lifting' surfaces. Previous research has shown that the side force, yawing moment, and rolling moment can be significantly reduced if a disturbance is continuously generated at the nose tip of a slender body. The experimental work placed 0- 3 strokes on the nose tip of a finned missile, and then spun the nose tip at various rates. The out-ofplane loading showed significant reduction throughout the angle of attack regime. Using discrete vortex theory, an analysis was performed to predict the experimental results for the spinning nose slender finned body. A comparison is then made between the theoretical and experimental results.