A NEW APPROACH TO FLOW-FIELD MEASUREMENT - A VIEW OF DOPPLER GLOBAL VELOCIMETRY TECHNIQUES

Nonintrusive techniques for determining velocities in fluid flowfields , based on the use of laser technology, have been the subject of much research over the last three decades. Many of these techniques, such a s laser-Doppler-anemometry (LDA) and laser-two-focus-anemometry (L2F), have been based on point-wise measurements until the advent, in the l ast decade, of particle image velocimetry (PIV). There is much interes t in pursuing the goal of nonintrusive, whole-field velocity measureme nts, although such techniques are still some way from maturity. A new technique has recently emerged to challenge the position of PIV: the t echnique of Doppler global velocimetry (DGV). This paper outlines the origins of the technique, the physical principles involved, and the po tential advantages of DGV over PIV. A review is made of the technology used by the small number of groups researching this new method, drawi ng comparisons between the major aspects of their differing techniques . Finally, examples are given of ''test case'' measurements of two wel l-established velocity fields: those of a rotating disc, and those in a subsonic open jet. (C) 1997 by Elsevier Science Inc.