RECENT APPLICATIONS OF PARTICLE IMAGE VELOCIMETRY IN AERODYNAMIC RESEARCH

Particle image velocimetry (PIV) is increasingly used to investigate u nsteady velocity fields instantaneously. For the first time the PIV te chnique allows the recording of a complete velocity field in a plane o f the flow within a few microseconds. The PIV technique thereby provid es information about unsteady flow fields which is difficult to obtain with other experimental techniques. The short acquisition times and f ast availability of data reduce the operational time, and hence cost, in large scale wind tunnels and test facilities. At DLR a variety of P IV systems for use in industrial wind tunnels has been developed in th e past decade. The flexibility of these portable systems is illustrate d by presenting several results of recent PIV applications. More recen tly the original photographic means of PIV image recording has been pa rtially replaced by high resolution electronic imaging which can provi de PIV data nearly on-line. Images recorded by either system use the s ame multiple-pass, cross-correlation analysis software, whose algorith ms are briefly described. Several examples of actual applications are given: the flow issuing from a jet nozzle was imaged by a specially de veloped high-speed video camera at close proximity. A high resolution dual-frame digital camera was applied in the study of helicopter rotor aerodynamics and wake Vortex measurements of an airplane model. Furth er, large image sequences exceeding 100 PIV recordings provided detail ed information on the structure of a turbulent boundary layer. (C) 199 7 Elsevier Science Ltd.