Experimental Investigations on the Phantom Yaw Effect on a maneuvering slender body

Abstract

This paper deals with the topic of asymmetric vortices on slender bodies at high angles of attack called the Phantom Yaw Effect. In contrast to most of the existing studies, the Phantom Yaw is investigated both on the still and on the moving body undergoing pitching motions with almost realistic pitch rates. Tests were performed at different Mach numbers (0.5 ≤ M ≤ 1.1) and Reynolds numbers (2.0 ≤
10^5  ReD ≤ 4.2 ≤
10^5) but only some of the results obtained at M = 0.8 and ReD = 4.2
∙ 10^5 are presented within this paper. The test model is a generic missile configuration with a blunt nose and a high fineness ratio of 20. With this model, the influence of the (nose) roll angle, as well as the effect of an asymmetric transition fixation (at the nose and shoulder section) on the formation of asymmetric vortices were studied. The tests showed that the asymmetry can be triggered but they also revealed that the mechanisms are not simple and the effects not always distinct. Furthermore, symmetrical longitudinal side-jets in the shoulder region (aerostrakes) were used to force a symmetric flow separation in order to reduce the occurring side forces and yawing moments. The tests showed that this device works well under static conditions (no model motion) but has deficiencies under dynamic conditions.