Fundamental aspects of the vortex flow on cones

A large number of studies of flow visualisations, developed on the upper surface of delta or gothic wings and of cones, have been carried out in the wind tunnel of the Valenciennes University Aerodynamics and Hydrodynamics Laboratory (LAH). These studies have provided a better understanding of the development and the positioning of vortex structures and have enabled, in particular, the preferential nature of intervortex angles, thereby defined, to be determined. Such a notable angular characterisation has revealed, in the case of delta and gothic wings, the existence of a simple law, that of filiation, which finds expression in an angular correspondence between the main vortex torque and the leading edges of the wing. The study of the vortical structures developed on the upper surface of cones has produced an equally simple definition, also called the law of filiation, which, by analogy, is applicable to an angular correspondence between the main and the secondary vortex torques. This paper, which limits itself to discussing the case of a cone having an included angle of 68.6°, provides a detailed description of the phenomenon. However, no current theory seems to be able to give a straightforward explanation of these behavioural properties.