Practical experiences in the application of particle image velocimetry to engineering fluid mechanics.

The 1980's have seen the rapid development of particle image velocimetry, often referred to as speckle velocimetry, as a new and powerful technique for obtaining non intrusive measurements of fluid flow. Two in plane components of velocity are obtained simultaneously at all points in an illuminated sheet of laser light where scattering centres exist. The sheet is provided by a pulsed laser or a strobed continuous wave laser so that a series of discrete images are seen either by a 'still' or video camera viewing along a normal to the illuminated plane. Post experimental data reduction uses a variety of image processing techniques to difference the images and thus obtain the in plane velocity components. The present paper describes the practical experiences of two years of experimentation developing the technique as a practical engineering tool. The operation of two systems is described.