Experimental Investigations on the Phantom Yaw Effect on a Maneuvering Slender Body

Abstract

Phantom Yaw can be induced by e.g. small perturbations or deviations in geometry which cause an asymmetric separation. Experiments were conducted investigating this phenomenon under both static (no model motion) and dynamic (pitching motions at almost realistic pitch rates) conditions. The tests were performed at M = 0.8 and ReD = 4.3*105 using a generic missile configuration. The effect of small geometric deviations on the Phantom Yaw was studied by changing the model’s roll angle. Additionally, the possibility of triggering asymmetric vortices by a fixed, asymmetric transition at the model’s nose and shoulder was investigated. Indeed, the asymmetry can be triggered but the mechanisms are complex and the effects not always distinct. Furthermore, two Phantom-Yaw-Reduction devices were tested. These were “conventional strakes“ and “aerostrakes“ (two symmetrical side-jets at the model’s shoulder). In combination with a fixed asymmetric transition, both devices revealed deficiencies and were not able to really reduce/suppress Phantom Yaw. Without this fixed transition, the aerostrakes worked well under static conditions but a reduction of the yawing moment was not always achieved within the maneuver simulations. With conventional strakes, no significant Phantom Yaw was measured under both static and dynamic conditions.