Quantitative flow field measurements in a catapult facility using particle image velocimetry

In order to investigate the long term behaviour of the wake vortex flow behind an aircraft, quantitative whole-field measurements have been carried out in a free flight analysis laboratory using the PIV (Particle Image Velocimetry) technique. Instantaneous velocity fields were measured in successive planes crosswise to the flight path of a free flying air-liner model, so that the evolution, interaction and decay of vortices originating from the wing, flap and slat tips can be described. The optical measurement system consisting of two aerosol generators for seeding, a pulsed laser system for illumination, two CCD cameras for image recording and trigger electronics for synchronisation had to be adapted to the particular test conditions of a catapult facility, where a long-lasting, unsteady "single event" initiated by the model's launch is subject of the experimental study. The paper focuses on the technical aspects of interfacing a catapult facility and a digital PIV system.