A two component LDA-system to be operated in a 3 x 3 sq m low speed windtunnel

A two component laser Doppler anemometer operated in backscatter mode with a focal length of 2300 mm has been built up in the DFVLR Goettingen. For use in large wind tunnels other requirements than for a laboratory system must be fulfilled. In particular positioning of the system, taking measurements in a reasonable time and achieving a quick-look-result must be performed automatically under computer control to save wind tunnel running time. Several tests under laboratory conditions and in a pipe flow have been undertaken in order to get familiar with the system and to improve critical optical components. Measurements on a prolate spheroid in the 3 x 3 sq m wind tunnel of the DFVLR were performed to test the system in a large wind tunnel. The experimental results are compared with theoretical predictions.