Mean flow and turbulence measurements in a half-delta wing vortex

A subsonic experimental study has been conducted to examine the mean and turbulent properties of a single longitudinal vortex generated by a half-delta wing. Measurements were made on fine cross-plane grids at seven streamwise locations using hot cross-wires. The evaluated streamwise vorticity contours indicated that the initially distorted vortex at a streamwise station equivalent to a half wing height became round by about three wing heights. In this initial " transition" region, where the vortex was still rolling-up, the peak vorticity dropped by about 50% following a X^{- 1 2} decay. In this region, the generator wake remained distinct from the region of maximum vorticity, although the two regions were seen to slowly merge together. The Reynolds stress contours were also distorted initially with the maximum values occurring in the generator wake region, rather than in the vortex core, but these also decayed rapidly. Downstream of the transition region, the vortex appeared to reach an equilibrium state with the regions of maximum vorticity and turbulent kinetic energy coincident and the levels approximately constant with increasing streamwise distance. Comparison with previous data on vortices produced by double-branched generators further confirmed that the present vortex had achieved a fully developed state, and in a relatively short streamwise distance.