The Investigation of Unsteady Flow Fields in Aerodynamics by Means of Particle Image Velocimetry

Abstract

Particle Image Velocimetry (PIV) is increasingly used to investigate unsteady velocity fields instantaneously. For the first time the PIV technique allows the recording of a complete velocity field in a plane of the flow within microseconds. PIV provides information about unsteady flow fields, that is difficult to obtain with other experimental techniques. It also helps to save operationaltime in the wind tunnel. At DLR a set up for PIV has been developed which can be operated under the rough environmental conditions (noise, vibrations) of large industrial wind tunnels, such as DNW. This system has been successfully applied to very low speed as well as to high speed flows (U &#61 1. 600 m/s) at a number of aerodynamicinvestigations such as e.g. in the field of grid turbulence, boundarylayer instabilities, rotors, wakes behind airfoils, and for the investigation of transonic flows in the wake of cascade blades. The evaluation and post-processing of the PIV recordings run fully.