The accurate determination of the velocity vector from a particle image velocimetry (PIV) transparency depends on the number of image pairs that have been recorded in the region under examination. If one particle pair is present, there is an ambiguity of rad in direction. Two particle pairs give four ambiguous velocity vectors. This paper describes a new approach in PIV that resolves the ambiguity problem and potentially increases the dynamic range of the technique.
Jeremy M. Coupland,
Christopher J. D. Pickering,
Neil A. Halliwell,
"Particle Image Velocimetry: The Ambiguity Problem," Optical Engineering 27(3), 273193 (1 March 1988). http://dx.doi.org/10.1117/12.7977910