Vortex Chararcteristics Analysed from HART Data

Abstract

This paper analyses the detailed data taken during the HART test 1994 on a pressure instrumented BO105 hingeless model rotor. Leading edge pressure distribution provides information, over which part of the rotor disk vortices passed on top, where they penetrate the disk and where they are below. The intensity of BVI is qualitatively visible. From pressure distribution along chord in the outer part of the blade, the load distribution and therewith the blade bound circulation can be computed. This results into the strength, sense of rotation, the number and the radial position of tip vortices trailed into the wake. Flow visualisation by LLS technique provides the vortex trajectories in space at a desired blade azimuth and the vortex passage height and time through the LDV measurement range, and its inclination angles with respect to the LDV position, can be derived from these data. 3D velocity vectors within a wide time window are available by LDV measurements along two vertical lines. These data provide information about the vortex structure, i.e. vorticity distribution, vector field, core radius, circulation, height and time of passage of the vortex center through the LDV measurement range. All of these data are used in this paper to analyse the vortex structures, to compare LLS and LDV results where possible and to point on noncompatibilities found between the results.