Vortex Interactions in Multiple Vortex Wakes behind Aircraft

Abstract

A flow visualization technique has been developed that allows the nature of lift-generate d wakes behind aircraft models to be investigated. The technique is applicable to models being towed underwater in a ship model basin. Several different configurations of a 0.61-m (2-ft) span model of a Boeing 747-type transport aircraft were tested to allow observation of typical vortex interactions and merging in multiple vortex wakes. The vortices were identified by emitting tracer dyes from selected locations on the model. Their trajectories were obtained from photographs of the wake. Wingspan loading and model attitude were found to effect both vortex motions within the wake and resulting far-field wake velocity. Landing-gear deployment caused a far-field reformation of vorticity behind a model configuration which dissipated concentrated vorticity in the near-field wake. Circulation from the wing always caused a downward movement of the horizontal tail vortices, which merged with wing vortices. A modified landing configuration was developed that appeared to significantly alleviate the concentrated wake vorticity associated with the current landing configuration.