Properties of aircraft wake vortices measured by ground-based continuous-wave Doppler lidar

The DLR ground-based cw Doppler lidar has been developped for wind and turbulence measurements in the Atmospheric Boundary Layer. Moreover, it is used for experimental investigations of aircraft wake vortices. By the present paper measurements of wake vortices generated by military-type fixed-wing as well as rotor-wing aircraft will be presented. The experimental data has been analysed regarding the structure and circulation of wake vortices, partly also regarding their temporal development. The influence of flight parameters has been measured during several consecutive fly-bys. Small variations in the velocity profiles could be observed which were overlayed by the signatures of the variable wind and turbulence field, a problem which can only be solved by statistical treatment. The influence of the aircraft design could be demonstrated by comparison of the vortex signatures generated by two B707-type aircraft with pronounced differences in aircraft design.