Application of Particle Image Velocimetry to Aerodynamic Investigations in Wind Tunnels

Abstract

The PIV technique, which allows an instantaneous and nonintrusive measurement of the flow velocity in a two-dimensional plane within the recording of a complete velocity field in a plane of the flow within microseconds. This does not only give information about unsteady flow fields otherwise not obtainable but also helps to save operational time in the wind tunnel. Generally, there exist a number of different possibilities to realize a PIV system, according to the fluid mechanical problem to be investigated. However, special requirements have to be fulfilled, when applying the PIV technique in large wind tunnels or at high flow velocities. At DLR a PIV system has been developed during the last years, which has been operated in different flow facilities as e.g. jet flow facility, low turbulence wind tunnel, 3 x 3 m hoch 2 low speed wind tunnel, and high-speed blow-down wind tunnel. Some improvements of the PIV technique had to be carried out in order to be able to utilize the PIV technique in a high speed wind tunnel with a measuring time of less than 20 seconds and in large wind tunnels where easy and fast operating of the PIV technique is required. Among these improvements are a fast focusing device for the recording camera, on-line observation of seeding with tracer particles, master control unit for automatic control of the whole measuring sequence and the parallel data acquisition of pressure, temperature, angle of incidence etc.