Photon correlation techniques for wind-tunnel anemometry

The experience gained at the Royal Aircraft Establishment in laser anemometry techniques, using a photon correlator, is reviewed. The theory of operation of the equipment is summarized for both laminar and turbulent flows, and methods of data-reduction are discussed, with particular reference to the optical criteria which should be met. Flow seeding requirements are considered and a practical system described. The results of a number of experiments on subsonic and supersonic airflows, both laminar and turbulent, are presented.