Characterization of Aircraft Wake Vortices by Multiple-Lidar Triangulation

Abstract

Three continuous-wave lidar systems have been deployed to measure simultaneously the aire ow associated with wake vortices generated by a medium-size full-scale test aircraft. The lidar systems were positioned to permit investigation of fundamental aspects of vortex behavior. Two lidars were located 27 m apart, along a line parallel to the glide slope. This allowed a consistency check via comparison of the two sets of results and gave an indication of axial variations in vortex location and character. The third lidar was positioned 80 m away along a line perpendicular to the glide slope. This permitted accurate location of the vortex cores by triangulation methods via a tracking algorithm based on an extended Kalman e lter, typically to an accuracy of better than § §4.0 m. The mean value of core separation for a vortex age of 2 s agrees to within 5% of that predicted for this aircraft using the approximation of elliptically distributed lift. Calculation of vortex circulation requires accurate information on vortex range in conjunction with tangent velocity proe les: The trajectories thus determined are an essential input, and, hence, this method will reduce the uncertainty in the values of circulation in comparison to studies involving only a single lidar.