Investigations of Unsteady Flow Fields in Transonic Wind Tunnels Using Particle Image Velocimetry

Abstract

Over the past two decades the non-intrusive Particle Image Velocimetry (PIV) has matured from its developmental stage in laboratory scale to a reliable whole field measurement technique in industrial wind tunnel applications. Figure 1 shows the simple principle of the PIV technique in a wind tunnel experiment. After seeding the flow with small tracer particles the instantaneous measurement of a whole velocity vector field in a plane of the flow can be performed within a few microseconds by using a double cavity pulse laser, light sheet- and imaging optics and a (digital) camera. Nowadays all three components of up to 10000 velocity vectors can be determined out of two simultaneously captured stereoscopic double images of illuminated particles inside the wind tunnel flow.