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An experiment is performed to investigate the feasibility of using a water tunnel to study the aircraft wake vortex behavior in ground effect. Two blades are used to generate the vortices, simulating an aircraft wake. The ground plane is modeled with a splitter plate. Vortex mean positions are determined using an optical technique. The results show all the critical properties of an aircraft wake in the vicinity of the ground. The vortices are shown to descend monotonically until they start interacting with the ground plane. The minimum height to which the filaments sink is shown to compare favorably with that predicted by numerical methods and the operational data obtained from lidar. The vortex span is shown to increase at the same rate as that estimated from an empirical model based on lidar data as well. Vortex rebound is observed with maximum heights comparing well with other predictions. Partial comparison is also presented with a numerical scheme developed for AVOSS application.

Dynamic interactions of pairs of co-rotating vortex filaments, typical of those emanating from wing tips and flap tips are studied. Time history of the motion of individual filaments has been obtained in a water tunnel using an optical method. It is demonstrated that before their merger, co-rotating vortex filaments tend to oscillate along preferred directions. Also, the motion appears to be unstable with increasing amplitude over a wide range of frequencies. These conclusions are shown to be consistent with analytical predictions. It is also shown that the merger location correlates well with the vortex strength. Comparisons with analytical and computational results are provided where appropriate.