Characterization of Trailing Line Vortices

Mean velocity surveys were taken for axial or trailing line vortices produced behind a bi-wing vortex generator in a low-speed wind tunnel. Data were taken primarily with a seven-hole probe at a speed of 30m/s; but vortex steadiness was studied using smoke flow visualization over a speed range between 10 and 40 m/s. Various generator center body configurations were studied, with particular interest directed toward how a centerline jet and an asymmetric, unsteady circumferential flow influenced the mean velocity profiles. This study found that a centerline jet did not produce a well-behaved two-cell vortex over the parametric range available in the wind tunnel. Mean velocity profiles that were produced when circumferential disturbances were introduced via the center body were found to be identical, within experimental error, to mean profiles produced behind the same configuration with the injection slots taped. Since vortex stability, with respect to vortex breakdown, has been delineated using Rossby number, steady vortex velocity profiles have been identified in terms of local Rossby and Reynolds number. Using an axial-based Reynolds number, these experiments covered a Reynolds number range of 8,900 to 21,400 and the Rossby number varied between 0.99 and 2.20.